CN104756238B - Method of controlling a switch-mode ion energy distribution system - Google Patents

Abstract

Systems, methods, and apparatus for regulating ion energy within a plasma chamber and clamping a substrate to a substrate support are disclosed. An exemplary method comprises: placing a substrate within a plasma chamber; forming a plasma within the plasma chamber; controllably switching electrical energy to the substrate to apply a periodic voltage function to the substrate; and modulating the periodic voltage function in response to a defined ion energy distribution of the surface of the substrate during a plurality of periods of the periodic voltage function so as to achieve the defined ion energy distribution on a time-averaged basis.

Description

Method of controlling a switch-mode ion energy distribution system

Related Cases and Priorities

This application is a continuation-in-part of US Patent Application No. 13/193,299, filed July 28, 2011 and a continuation-in-part of nonprovisional US Patent Application No. 12/870,837, filed August 29, 2010. The details of Application Nos. 13/193,299 and 12/870,837 are incorporated by reference in their entireties into this application for all appropriate purposes.

technical field

The present disclosure generally relates to plasma processing. In particular, but not limited to, the present invention relates to methods and apparatus for plasma assisted etching, deposition, and/or other plasma assisted processes.

Background technique

Many types of semiconductor devices are fabricated using plasma-based etching techniques. If the conductor is etched, a negative voltage with respect to ground can be applied to the conductive substrate to create a substantially uniform negative voltage across the surface of the substrate conductor, which attracts positively charged ions towards the conductor, and as a result , the positive ions that collide with the conductor have essentially the same energy.

However, if the substrate is a dielectric, the constant voltage has no effect on the voltage across the surface of the substrate. But an AC voltage (eg high frequency) can be applied to the conductive plate (chuck) so that the AC region induces a voltage at the surface of the substrate. During the positive half of the AC cycle, the substrate attracts electrons which are light in mass relative to the positive ions; thus many electrons will be attracted to the surface of the substrate during the positive half cycle. As a result, the surface of the substrate will be negatively charged, so that ions will be attracted to the negatively charged surface. And when the ions strike the surface of the substrate, the impact dislodges material from the surface of the substrate, completing the etch.

In many cases, a narrow ion energy distribution is desired, but applying a sine wave to the substrate induces a broad ion energy distribution, which limits the ability of the plasma process to perform the desired etch profile. Known techniques for achieving narrow ion energy distributions are expensive, inefficient, difficult to control, and can adversely affect plasma density. As a result, these known techniques have not been adopted commercially. Accordingly, what is needed is a system and method that addresses the deficiencies of the current technology and provides other novel and inventive features.

Contents of the invention

Exemplary embodiments of the present disclosure illustrated in the drawings are summarized below. These and other embodiments are described more fully in the Detailed Description section. It should be understood, however, that there is no intention to limit the invention to the forms described in this Summary or Detailed Description. Those skilled in the art can recognize that there are many modifications, equivalents and alternative constructions which would fall within the spirit and scope of the invention as expressed in the claims.

According to one embodiment, the invention may be characterized as a method for establishing one or more plasma sheath voltages. The method may include providing the modified periodic voltage function to the substrate support of the plasma chamber. The substrate support may be coupled to a substrate configured for processing in a plasma. Likewise, the modified periodic voltage function may comprise a periodic voltage function modified by ion current compensation Ic. The modified periodic voltage function may include pulses and portions between the pulses. Likewise, the pulses may be a function of the periodic voltage function and the slope of the portion between the pulses may be a function of the ion current compensation Ic. The method may further comprise accessing _an effective capacitance value Ci representing at least the capacitance of the substrate support. The method may ultimately identify _a value of the ion current compensation Ic that will produce a defined ion energy distribution function for ions reaching the surface of the substrate, wherein the identification is the effective capacitance C and the A function of the slope dV ₀ /dt of the portion between pulses.

According to another embodiment, the invention may be described as a method for biasing a plasma to achieve a defined ion energy at the surface of a substrate within a plasma processing chamber. The method may include applying to the substrate support a modified periodic voltage function comprising a periodic voltage function modified by ion current compensation. The method may also include sampling at least one cycle of the modified periodic voltage function to generate voltage data points. The method may also include estimating a value of a first ion energy at the substrate surface from the voltage data points. Likewise, the method may comprise adjusting the modified periodic voltage function until the first ion energy is equal to the defined ion energy.

According to yet another embodiment, the invention can be characterized as a method to achieve the breadth of the ion energy distribution function. The method can include providing a modified periodic voltage function to a substrate support of a plasma processing chamber. The method may also include sampling at least two voltages from the non-sinusoidal waveform at a first time instant and at a second time instant. The method may additionally comprise calculating the slope of the at least two voltages as dV/dt. Likewise, the method may include comparing the slope to a known reference slope to correspond to an ion energy distribution function width. Finally, the method may include adjusting the modified periodic voltage function such that the slope approaches the reference slope.

Another aspect of the disclosure can be characterized as an apparatus including a power supply, an ion current compensation component, and a controller. The power supply may provide a periodic voltage function having pulses and portions between the pulses. The ion current compensation component may modify the slope of the portion between the pulses to form a modified periodic voltage function. The modified periodic voltage function may be configured for provision to a substrate support for processing in a plasma processing chamber. The controller may be coupled to the switched mode power supply and the ion current compensation component. The controller may be further configured to identify a value of the ion current compensation that, if provided to the substrate support, would result in a defined ion energy distribution of ions reaching the surface of the substrate function.

Yet another aspect of the present disclosure can be characterized as a non-transitory tangible computer readable storage medium encoded with processor readable instructions to perform a method for monitoring an ion current of a plasma configured to process a substrate method. The method may include sampling a modified periodic voltage function taking into account ion current compensation having a first value, and taking into account said ion current compensation having a second value, sampling said modified The periodic voltage function is sampled. The method may also include determining a slope of the modified periodic voltage function as a function of time based on the first sample and the second sample. The method also determines a slope of the modified periodic voltage function as a function of time based on the first sample and the second sample. The method may ultimately include calculating a third value of the ion current compensation based on the slope at which the constant voltage across the substrate will be at least exist within one cycle.

These and other embodiments are described in further detail herein.

Description of drawings

Various objects and advantages and a more complete understanding of the present invention will become apparent and more readily understood by reference to the following detailed description and appended claims when taken in conjunction with the accompanying drawings, wherein like reference numerals refer to throughout the several drawings Identical or similar elements, and in the drawings:

Figure 1 shows a block diagram of a plasma processing system according to one embodiment of the present invention;

FIG. 2 is a block diagram illustrating an exemplary embodiment of the switched-mode power supply system shown in FIG. 1;

FIG. 3 is a schematic representation of components that may be used to implement the switch-mode bias power supply described with reference to FIG. 2;

FIG. 4 is a timing diagram showing two drive signal waveforms;

5 is a graphical representation of a single mode of operating a switched mode bias power supply to achieve an ion energy distribution focused at a particular ion energy;

Figure 6 is a diagram illustrating a dual-modal mode of operation in which two discrete peaks in the ion energy distribution are generated;

7A and 7B are diagrams showing actual, direct ion energy measurements made in a plasma;

Figure 8 is a block diagram illustrating another embodiment of the present invention;

Figure 9A is a graph showing an exemplary periodic voltage function modulated by a sinusoidal modulation function;

Figure 9B is an exploded view of a portion of the periodic voltage function shown in Figure 9A;

Figure 9C shows the time-averaged resulting ion energy distribution resulting from the sinusoidal modulation of the periodic voltage function;

Figure 9D shows actual direct ion energy measurements made in a plasma of the time-averaged IEDF obtained when the periodic voltage function is modulated by a sinusoidal modulation function;

Figure 10A shows a periodic voltage function modulated by a sawtooth modulation function;

Figure 10B is an exploded view of a portion of the periodic voltage function shown in Figure 10A;

Figure 10C is a graph showing the time-averaged resulting distribution of ion energies resulting from the sinusoidal modulation of the periodic voltage function in Figures 10A and 10B;

Figure 11 is a diagram showing the IEDF function in the right column and the associated modulation function in the left column;

Figure 12 is a block diagram illustrating an embodiment in which ion current compensation components compensate for ion current within a plasma chamber;

Figure 13 is a diagram showing exemplary ion current compensation components;

FIG. 14 is a graph showing exemplary voltages at the node Vo shown in FIG. 13;

15A-15C are voltage waveforms occurring at the surface of a substrate or wafer in response to a compensation current;

FIG. 16 is an exemplary embodiment of a current source that may be implemented to implement the current source described with reference to FIG. 13;

17A and 17B are block diagrams illustrating other embodiments of the present invention;

Figure 18 is a block diagram illustrating another embodiment of the present invention;

Figure 19 is a block diagram illustrating yet another embodiment of the present invention;

Figure 20 is a block diagram of input parameters and control outputs that may be used in conjunction with the embodiments described with reference to Figures 1-19;

Figure 21 is a block diagram illustrating yet another embodiment of the present invention;

Figure 22 is a block diagram illustrating yet another embodiment of the present invention;

Figure 23 is a block diagram illustrating yet another embodiment of the present invention;

Figure 24 is a block diagram illustrating yet another embodiment of the present invention;

Figure 25 is a block diagram illustrating yet another embodiment of the present invention;

Figure 26 is a block diagram illustrating yet another embodiment of the present invention;

Figure 27 is a block diagram illustrating yet another embodiment of the present invention;

Figure 28 illustrates a method according to an embodiment of the disclosure;

Figure 29 shows another method according to an embodiment of the present disclosure;

Figure 30 illustrates one embodiment of a method of controlling the ion energy distribution of ions striking a surface of a substrate;

Figure 31 shows a method for setting the IEDF and ion energy;

Figure 32 shows two modified periodic voltage function waveforms delivered to a substrate support according to one embodiment of the present disclosure;

Figure 33 shows ion current waveforms that can be indicative of plasma source instabilities or changes in plasma density;

Figure 34 shows the ion current _II with a modified periodic voltage function waveform having a non-periodic shape;

Figure 35 shows a modified periodic voltage function waveform that may indicate a fault within the bias supply;

Figure 36 shows a modified periodic voltage function waveform that can indicate dynamic changes in system capacitance;

Figure 37 shows a modified periodic voltage function waveform that can indicate a change in plasma density;

Figure 38 shows sampling of ion currents for different process runs, where drift in ion current may indicate system drift;

Figure 39 shows sampling of ion current for different process parameters.

Figure 40 shows two bias waveforms monitored with no plasma in the chamber;

Figure 41 shows two bias waveforms that can be used to verify the plasma process;

Figure 42 shows several supply voltage and ion energy graphs showing the relationship between supply voltage and ion energy;

Figure 43 illustrates one embodiment of a method of controlling the ion energy distribution of ions striking a surface of a substrate;

Figure 44 shows various waveforms at various points in the system disclosed herein;

Figure 45 shows the effect of making a final incremental change in the ion current compensation Ic so that it matches the ion current _II ;

Figure 46 shows the selection of ion energy;

Figure 47 illustrates selection and expansion of ion energy distribution function width;

Figure 48 shows one mode of supply voltage V _PS that can be used to achieve more than one ion energy level, where each ion energy level has a narrow IEDF width;

Figure 49 shows another mode of supply voltage V _PS that can be used to achieve more than one ion energy level, where each ion energy level has a narrow IEDF width; and

Figure 50 shows one combination of supply voltage V _PS and ion current compensation IC that can be used to create the defined _IEDF .

detailed description

An exemplary embodiment of a plasma processing system is generally shown in FIG. 1 . As shown, plasma power supply 102 is coupled to plasma processing chamber 104 and switched mode power supply 106 is coupled to support 108 upon which substrate 110 is placed within chamber 104 . Also shown is a controller 112 coupled to the switch mode power supply 106 .

In the exemplary embodiment, plasma processing chamber 104 may be implemented as a chamber of substantially conventional construction (eg, including a vacuum enclosure evacuated by one or more pumps (not shown)). Furthermore, those skilled in the art will understand that the plasma in chamber 104 may be excited by any source, including, for example, a helical plasma source that includes magnetic coils to energize and maintain plasma 114 in the reactor. and antenna, and a gas inlet may be provided to introduce gas into the chamber 104 .

As shown, the exemplary plasma chamber 104 is configured and configured for plasma-assisted material etching. The plasma power supply 102 in this embodiment is configured to apply energy (eg, RF energy) to the chamber 104 via a matching network (not shown) at one or more frequencies (eg, 13.56 MHz) to energize and maintain plasma114. It should be understood that the present invention is not limited to any particular type of plasma power supply 102 or source used to couple energy to chamber 104 and that various frequencies and energy levels may be capacitively or inductively coupled to plasma 114 .

As shown, a dielectric substrate 110 (e.g., a semiconductor wafer) to be processed is at least partially supported by a support 108, which may comprise a portion of a conventional wafer chuck (e.g., for semiconductor wafer processing) . The support 108 may be formed with an insulating layer between the support 108 and the substrate 110 , where the substrate 110 is capacitively coupled to the platform, but the support 108 may also float at a different voltage than the support 108 .

As mentioned above, if both the substrate 110 and the support 108 are conductors, a constant voltage can be applied to the support 108, and due to electrical conduction through the substrate 110, the voltage applied to the support 108 is also applied to the substrate. The surface of the bottom 110.

However, applying a constant voltage to the support 108 has no effect on generating a voltage across the treated surface of the substrate 110 when the substrate 110 is a dielectric. Accordingly, the exemplary switched-mode power supply 106 is configured to be controlled to achieve a voltage on the surface of the substrate 110 that attracts ions in the plasma 114 to collide with the substrate 110 to perform a controlled etch of the substrate 110 and/or or deposition and/or other plasma assisted processes.

Furthermore, as discussed further herein, switch-mode power supply 106 of an embodiment is configured to operate such that there is substantially There is no interaction on . For example, the energy applied by controlling the switch mode power supply 106 is controllable so that ion energy can be controlled without substantially affecting the plasma 114 density.

Furthermore, many of the embodiments of the exemplary switched-mode power supply 106 shown in FIG. 1 are implemented from relatively inexpensive components that can be controlled by relatively simple control algorithms. And many embodiments of the switch mode power supply 106 are much more efficient than the prior art; thereby reducing energy costs and expensive materials associated with removing excess thermal energy.

One known technique for applying a voltage to a dielectric substrate utilizes a high power linear amplifier combined with a complex control scheme to apply energy to the substrate support which induces a voltage on the substrate surface. However, this technology has not been adopted by commercial entities because it has not proven to be cost-effective and easy to manage. Specifically, the linear amplifiers used are usually large, very expensive, inefficient and difficult to control. Furthermore, linear amplifiers inherently require AC coupling (eg, DC blocking capacitors), and additional chuck-like functions are performed by parallel feed circuits, which compromise the AC spectral cleanliness of systems with chucked sources.

Another technique that has been considered is to apply high frequency power to the substrate (eg, using one or more linear amplifiers). However, this technique has been found to adversely affect plasma density due to the effect of high frequency power applied to the substrate on plasma density.

In some embodiments, the switch-mode power supply 106 shown in FIG. 1 may be implemented by buck, boost, or buck-boost type energy technology. In these embodiments, the switched-mode power supply 106 may be controlled to apply varying levels of pulsed power to induce an electrical potential on the surface of the substrate 110 .

In other embodiments, the switch mode power supply 106 may be implemented by other more complex switch mode power supply and control techniques. Referring next to FIG. 2, for example, the switch-mode power supply described with reference to FIG. The energetic ions that bombard the substrate 110 . Also shown is an ion energy control component 220 , an arc detection component 222 , and a controller 212 coupled to both a switched mode bias power supply 206 and a waveform memory 224 .

The arrangement of these components shown is rational; thus in a practical implementation these components can be combined or further separated and connected in various ways without changing the basic operation of the system. For example, in some embodiments, both the power supply 202 and the switch-mode bias power supply 206 may be controlled by a controller 212 , which may be implemented in hardware, software, firmware, or a combination thereof. However, in an alternate embodiment, the power supply 202 and the switch-mode bias power supply 206 are implemented by entirely separate functional units. By way of further example, controller 212, waveform memory 224, ion energy control 220, and switch mode bias power supply 206 may be integrated into a single component (eg, in a common housing) or may be distributed among discrete components.

The switch-mode bias power supply 206 in this embodiment is generally configured to apply a voltage to the support 208 in a controllable manner to achieve a desired (defined) energy distribution of ions bombarding the substrate surface. More specifically, the switch-mode bias power supply 206 is configured to achieve a desired (defined) ion energy distribution by applying one or more specific waveforms at specific energy levels to the substrate. And more specifically, in response to input from ion energy control section 220, switch mode bias power supply 206 applies a specific energy level to achieve a specific ion energy, and utilizes one or more voltages defined by waveform data in waveform memory 224 waveform to apply a specific energy level. Accordingly, one or more specific ion bombardment energies may be selected using the ion control to perform a controlled etch (or other form of plasma processing) of the substrate.

As shown, the switched mode power supply 206 includes switching components 226', 226" (eg, high power field effect transistors) for switching energy to The support portion 208 of the substrate 210 . And the drive signals 230', 230" generated by the drive components 228', 228" are controlled by the controller 212 based on timing defined by the contents of the waveform memory 224. For example, the controller 212 in many embodiments is adapted to interpret the contents of the waveform memory and generate drive control signals 232', 232", which are utilized by the drive components 228', 228" to control the switching components to 226 ′, 226 ″ drive signals 230 ′, 230 ″. Although two switching components 226 ′, 226 ″ that may be arranged in a half-bridge configuration are shown for exemplary purposes, it is certainly conceivable that in various architectures the Fewer or additional switching components are implemented (eg, H-bridge configuration).

In various modes of operation, the controller 212 modulates (e.g., using waveform data) the timing of the drive control signals 232', 232" to achieve a desired waveform at the support 208 of the substrate 210. Additionally, the switched-mode power supply 206 is based on The ion energy control signal 234 provides power to the substrate 210, and the control signal 234 can be a DC signal or a time-varying waveform. Therefore, this embodiment can control the timing signal to the switching components and control the timing signals applied by the switching components 226', 226". The energy (controlled by the ion energy control unit 220) to control the ion energy distribution.

Additionally, controller 212 in this embodiment is configured to perform arc management functions in response to an arc within plasma chamber 204 detected by arc detection component 222 . In some embodiments, when an arc is detected, the controller 212 alters the drive control signals 232', 232", such that the waveform applied to the output 236 of the switch-mode power supply 206 extinguishes the arc in the plasma 214. In other implementations In one example, the controller 212 extinguishes the arc by simply interrupting the application of the drive control signals 232', 232", such that the application of energy to the output 236 of the switch-mode bias power supply 206 is interrupted.

Reference is next made to FIG. 3 , which is a schematic representation of components that may be used to implement the switch-mode bias power supply 206 described with reference to FIG. 2 . As shown, the switching elements T1 and T2 in this embodiment are arranged in a half bridge (also known as totem pole) type topology. Collectively, R2, R3, C1, and C2 all represent the plasma load, C10 is the effective capacitance (also referred to herein as series capacitance or chuck capacitance), and C3 is an optional physical capacitor to prevent The induced voltage or DC current from the voltage of the electrostatic chuck (not shown) flows through the circuit. C10 is referred to as the effective capacitance because it includes the series capacitance of the substrate support and the electrostatic chuck (or e-chuck) (or also known as the chuck capacitance) as well as other capacitances inherent to the application of bias, such as insulation and substrate. As shown, L1 is the stray inductance (eg, the inherent inductance of a conductor feeding power to the load). And in this embodiment, there are three inputs: Vbus, V2 and V4.

V2 and V4 represent drive signals (e.g., drive signals 230', 230" output by drive components 228', 228" described with reference to FIG. / or mutually delayed) so that the closing of T1 and T2 can be modulated to control the waveform of the voltage output Vout applied to the substrate support. In many implementations, neither of the transistors used to implement switching components T1 and T2 is an ideal switch, so in order to achieve the desired waveforms, transistor specific characteristics are considered. In many modes of operation, simply varying the timing of V2 and V4 can achieve the desired waveform to be applied at Vout.

For example, the switches T1, T2 may be operated such that the voltage at the surface of the substrate 110, 210 is generally negative and the periodic voltage pulse approaches and/or slightly exceeds the positive voltage reference. The voltage value at the surface of the substrate 110, 210 is a value defining ion energy, which may be characterized in terms of an ion energy distribution function (IEDF). To achieve the desired voltage at the surface of the substrate 110, 210, the pulse at Vout is generally rectangular and has a width long enough to induce a brief positive voltage at the surface of the substrate 110, 210 to attract sufficient electrons to the substrate. The bottom 110, 210 surfaces to achieve the desired voltage and corresponding ion energy.

Periodic voltage pulses approaching and/or slightly exceeding the positive voltage reference may have a minimum time limited by the switching capabilities of the switches T1, T2. The substantially negative portion of the voltage may extend as long as the voltage does not build up to a level that damages the switch. At the same time, the length of the negative part of the voltage should exceed the ion transit time.

Vbus in this embodiment defines the pulse amplitude measured at Vout, which defines the voltage at the substrate surface as well as the ion energy. Referring briefly again to FIG. 2, Vbus may be coupled to an ion energy control, which may be implemented by a DC power supply for applying a DC signal or time-varying waveform to Vbus.

The pulse width, pulse shape, and/or mutual delay of the two signals V2, V4 can be modulated to achieve a desired waveform at Vout (also referred to herein as a modified periodic voltage function), and the voltage applied to Vbus can affect the characteristic. In other words, the voltage Vbus can affect the pulse width, pulse shape and/or relative phase of the signals V2, V4. For example, referring briefly to FIG. 4 , a timing diagram is shown showing two drive signal waveforms (as V2 and V4 ) that may be applied to T1 and T2 to produce a periodic voltage function at Vout as shown in FIG. 4 . The timing of the two gate drive signals V2, V4 can be controlled in order to modulate the pulse shape at Vout (eg, to achieve the minimum time of the pulse of Vout, but also the peak value of the pulse).

For example, two gate drive signals V2, V4 may be applied to the switching elements T1, T2, whereby each pulse applied at Vout may be short in time compared to the time T between pulses, but long enough to be in A positive voltage is induced on the surface of the substrate 110, 210 to attract electrons to the surface of the substrate 110, 210. Furthermore, it has been found that by varying the gate voltage level between pulses, the slope of the voltage applied to Vout between pulses can be controlled (eg, to achieve a substantially constant voltage at the substrate surface between pulses). In some modes of operation, the repetition rate of the gate pulses is approximately 400kHz, but this repetition rate will necessarily vary depending on the application.

Although not required, in practice, from modeling and refinement based on actual implementations, waveforms that can be used to generate desired (defined) ion energy distributions can be defined and stored (e.g., in the reference graph 1 described in the waveform memory section, as a sequence of voltage levels). Additionally, in many implementations, waveforms can be generated directly (eg, without feedback from Vout); thus, undesirable aspects of feedback control systems (eg, set times) are avoided.

Referring again to FIG. 3, Vbus can be modulated to control ion energy, and the stored waveform can be used to control gate drive signals V2, V4 to achieve the desired pulse amplitude at Vout while minimizing the pulse width. Again, this can be done in terms of specific characteristics of transistors that can be modeled or implemented and established empirically. For example, referring to FIG. 5 , there is shown a graph of Vbus varying with time, the voltage at the surface of the substrate 110 , 210 varying with time, and the corresponding ion energy distribution.

The diagram in Figure 5 shows a single mode of operation of the switch mode bias power supply 106, 206, which achieves ion energy distribution at a particular ion energy concentration. As shown, to achieve concentration of individual ion energies in this example, the voltage applied to Vbus is held constant while the voltages applied to V2 and V4 are controlled (e.g., using the drive signals shown in FIG. 3 ) so that Pulses are generated at the output of the switch mode bias power supply 106, 206 which achieve the corresponding ion energy distribution shown in FIG.

As shown in FIG. 5 , the potential of the surface of the substrate 110 , 210 is generally negative to attract ions that bombard and etch the substrate 110 , 210 . Periodic short pulses applied to the substrate 110, 210 (by pulsing Vout) have a magnitude defined by the potential applied to Vbus, and these pulses result in small changes in the potential of the substrate 110, 210 (e.g., close to Positive or slightly positive potential), which attracts electrons to the substrate surface so as to achieve a substantially negative potential along the surface of the substrate 110, 210. As shown in Figure 5, a constant voltage applied to Vbus achieves a concentration of individual ion flux at a specific ion energy; thus, a specific ion bombardment energy can be selected by simply setting Vbus to a specific potential. In other modes of operation, two or more separate concentrations of ion energies may be created (eg, see FIG. 49 ).

Those skilled in the art will recognize that the power supply need not be limited to a switch mode power supply, and as such, the output of the power supply can also be controlled in order to affect a certain ion energy. As such, the output of a power supply (whether switched mode or otherwise) may also be referred to as the supply voltage V _PS when considered without combination with ion current compensation or ion current.

Referring to FIG. 6 , for example, a diagram of a dual mode mode of operation that produces two separate peaks in the ion energy distribution is shown. As shown, in this mode of operation, the substrate is subjected to two distinct levels of voltage and periodic pulses, and thus two separate concentrations of ion energy are created. As shown, to achieve two distinct ion energy concentrations, the voltage applied at Vbus alternates between two levels, and each level defines an energy level for the two ion energy concentrations.

Although Figure 6 shows the two voltages of the substrate 110, 210 alternating after each pulse (eg, Figure 48), this is certainly not required. For example, in other modes of operation, the voltages applied to V2 and V4 are switched relative to the voltage applied to Vout (e.g., using the drive signals shown in FIG. 3 ) such that the induced voltage at the substrate surface Alternating from the first voltage to the second voltage (and vice versa) after two or more pulses (eg, FIG. 49 ).

In the prior art, attempts have been made to apply the combination of two waveforms (generated by the waveform generator) to a linear amplifier and apply the amplified combination of the two waveforms to the substrate in order to achieve multiple ion energies. However, this method is much more complex than that described with reference to Figure 6 and requires expensive linear amplifiers and waveform generators.

Referring next to Figures 7A and 7B, there are shown graphs of actual direct ion energy measurements made in a plasma corresponding to single-energy and bi-level modulation of the DC voltage applied to Vbus, respectively. As shown in FIG. 7A, in response to a constant voltage applied to Vbus (eg, as shown in FIG. 5), the ion energy distribution is centered around 80 eV. And in FIG. 7B, in response to a bi-level adjustment of Vbus (eg, as shown in FIG. 6), two separate ion energies exist concentrated around 85eV and 115eV.

Referring next to FIG. 8 , there is shown a block diagram illustrating another embodiment of the present invention. As shown, switched mode power supply 806 is coupled to controller 812 , ion energy control component 820 , and substrate support 808 via arc detection component 822 . The controller 812, the switch mode power supply 806 and the ion energy control unit 820 work together to apply energy to the substrate support 808 to achieve a desired (defined) ion energy distribution on the surface of the substrate 810 on a time-averaged basis .

Referring briefly to FIG. 9A , for example, a periodic voltage function with a period of about 400 kHz is shown, which is modulated by a sinusoidal modulation function of about 5 kHz during a number of cycles of the periodic voltage function. Fig. 9B is an exploded view of a portion of the periodic voltage function cycled in Fig. 9A, and Fig. 9C shows the resulting distribution of ion energies on a time-averaged basis resulting from sinusoidal modulation of the periodic voltage function. And Fig. 9D shows actual direct ion energy measurements in plasmas of time-averaged IEDFs obtained when the periodic voltage function is modulated by a sinusoidal modulation function. As discussed further herein, achieving a desired (defined) ion energy distribution on a time-averaged basis can be achieved by simply varying the modulation function applied to the periodic voltage.

Referring to FIGS. 10A and 10B as another example, a 400 kHz periodic voltage function is modulated by a sawtooth modulation function of approximately 5 kHz to achieve the ion energy distribution shown in FIG. 10C on a time averaged basis. As shown, the periodic voltage function used in connection with FIG. 10 is the same as FIG. 9 except that the periodic voltage function in FIG. 10 is modulated by a sawtooth function rather than a sinusoidal function.

It should be appreciated that the ion energy distribution functions shown in FIGS. 9C and 10C do not represent the instantaneous ion energy distribution at the surface of the substrate 810, but instead represent time-averaged ion energies. Referring to Fig. 9C, for example, at a particular moment, the ion energy distribution will be a subset of the shown ion energy distribution that exists over the entire period of the modulation function.

It should also be realized that the modulation function need not be a fixed function, nor need it be a fixed frequency. In some cases, for example, it may be desirable to modulate a periodic voltage function with one or more periods of a particular modulation function to achieve a particular, time-averaged ion energy distribution, and then to have one or more other The period of the modulation function is modulated by a periodic voltage function to achieve another time-averaged ion energy distribution. Such a change to the modulation function (that modulates the periodic voltage function) can be advantageous in many cases. For example, if a particular ion energy distribution is required to etch a particular geometry or etch through a particular material, a first modulation function can be used, and then another modulation function can subsequently be used to achieve a different etch geometry or etch through another a material.

Similarly, periodic voltage functions (e.g., the 400kHz component in Figures 9A, 9B, 10A, and 10B and Vout in Figure 4) do not have to be strictly fixed (e.g., the shape and frequency of the periodic voltage function can vary), but typically its frequency Determined by the transit time of the ions in the chamber such that the ions in the chamber are affected by the voltage applied to the substrate 810 .

Referring back to FIG. 8 , the controller 812 provides drive control signals 832 ′ and 832 ″ to the switch-mode power supply 806 such that the switch-mode power supply 806 generates a periodic voltage function. The switch-mode power supply 806 can be implemented by the components shown in FIG. 3 ( For example, create the periodic voltage function shown in Figure 4), although it is certainly conceivable that other switching architectures could be utilized.

In general, ion energy control component 820 functions to apply a modulation function (generated by controller 812 in conjunction with switched mode power supply 806 ) to a periodic voltage function. As shown in FIG. 8 , the ion energy control unit 820 includes a modulation controller 840 in communication with a custom IEDF section 850 , an IEDF function memory 848 , a user interface 846 and a power supply unit 844 . It should be appreciated that these components are shown to represent functional components, which in practice may be implemented by the same or different components.

The modulation controller 840 in this embodiment typically controls the power supply section 844 (and its output 834) based on data defining the modulation function, and the power supply section 844 (based on the control signal 842 from the modulation controller 840) generates the modulation function 834, which will Modulation function 834 is applied to the periodic voltage function generated by switch mode power supply 806 . The user interface 846 in this embodiment is configured to enable the user to select a predefined IEDF function stored in the IEDF function memory 848 , or to define a custom IEDF in conjunction with the custom IEDF component 850 .

In many implementations, the power supply section 844 includes a DC power supply (eg, a DC switch-mode power supply or a linear amplifier) that applies a modulated voltage (eg, a varying DC voltage) to a switch-mode power supply (eg, as shown in FIG. Vbus of the switch-mode power supply). In these embodiments, the modulation controller 840 controls the voltage level output by the power supply component 844 such that the power supply component 844 applies a voltage consistent with the modulation function.

In some implementations, the IEDF function store 848 includes a plurality of data sets corresponding to each of the plurality of IEDF distribution functions, and the user interface 846 enables a user to select a desired (defined) IEDF function. Referring to FIG. 11, for example, the right column shows exemplary IEDF functions available for user selection. And the left column shows the associated modulation function that the modulation controller 840 applies to the periodic voltage function in conjunction with the power supply unit 844 to implement the corresponding IEDF function. It should be appreciated that the IEDF functions shown in FIG. 11 are exemplary only and other IEDF functions may also be selected.

The custom IEDF component 850 generally functions to enable a user to define a desired (defined) ion energy distribution function through the user interface 846 . In certain embodiments, for example, a custom IEDF component 850 enables a user to determine values for specific parameters that define ion energy distributions.

For example, a custom IEDF component 850 allows for relative flux levels (e.g., in terms of percentages of flux) at high level (high IF), medium level (mid IF), and low level (low IF) The IEDF function is defined in combination with one or more functions defining the IEDF between these energy levels. In many cases, only the IEDF function between high IF, low IF and these levels is sufficient to define the IEDF function. As a specific example, a user may request 1200 eV for the 20% contribution level, 1200 eV for the 30% contribution level with a sinusoidal IEDF between the 20% contribution level (contribution to the total IEDF) and the 30% contribution level. 700eV.

It is also contemplated that the custom IEDF section 850 may enable a user to populate a table with a list of one or more (eg, multiple) energy levels and the corresponding percentage contribution of each energy level to the IEDF. And in another alternative embodiment, it is contemplated that the custom IEDF component 850 in conjunction with the user interface 846 enables the user to graphically generate a desired (defined) IEDF by presenting the user with a graphical tool that enables the user to draw the desired (defined) IEDF defined) IEDF.

It is also contemplated that the IEDF function memory 848 and the custom IEDF component 850 can interoperate to enable the user to select a predefined IEDF function and then alter the predefined IEDF function in order to generate a custom IEDF function derived from the predefined IEDF function. IEDF function.

Once the IEDF function is defined, the modulation controller 840 converts the data defining the desired (defined) IEDF function into a control signal 842 that controls the power supply unit 844 such that the power supply unit 844 implements a function corresponding to the desired (defined) IEDF modulation function. For example, the control signal 842 controls the power supply component 844 such that the power supply component 844 outputs a voltage defined by the modulation function.

Reference is next made to FIG. 12 , which is a block diagram illustrating an embodiment of ion current compensation component 1260 compensating for ion current within plasma chamber 1204 . Applicants have found that at higher energy levels, higher levels of ion current in the chamber affect the voltage at the substrate surface and, as a result, the ion energy distribution is also affected. Referring briefly to FIGS. 15A-15C , for example, voltage waveforms and their relationship to the IEDF are shown as they appear at the substrate 1210 or wafer surface.

More specifically, Figure 15A shows the periodic voltage function of the substrate 1210 surface when the ion current I _I is equal to the compensation current Ic; Figure 15B shows the voltage waveform on the substrate 1210 surface when the ion current I _I is greater than the compensation current Ic ; and FIG. 15C shows the voltage waveform on the substrate surface when the ion current I _I is less than the compensation current Ic.

As shown in FIG. 15A , when I _I =Ic, the spread 1470 of ion energies is relatively narrower than the uniform spread 1472 of ion energies shown in FIG. 15B when I _I >Ic, or in Uniform spread 1474 of ion energy when _II < Ic shown in 15C. Thus, the ion current compensation component 1260 achieves a narrow spread of ion energy when the ion current is high (e.g., by compensating for the effects of the ion current), and also enables a uniform spread 1572, 1574 of the ion energy that is controllable (e.g., when desired with ion energy extension).

As shown in Figure 15B, without ion current compensation (when I _I > Ic), the voltage at the substrate surface becomes smaller in a ramp-like fashion between the positive parts of the periodic voltage function Negatively, this produces a wider ion energy spread 1572. Similarly, when ion current compensation is used to increase the level of compensation current until the level of ion current (I _I < Ic) is exceeded as shown in FIG. 15C, between the positive part of the periodic voltage function, the substrate The voltage at the bottom surface becomes more negative in a ramped fashion and produces a wider uniform ion energy spread 1574 .

Referring back to FIG. 12 , ion current compensation component 1260 can be implemented as a separate accessory that can optionally be added to switch mode power supply 1206 and controller 1212 . In other embodiments, (eg, as shown in FIG. 13 ), ion current compensation component 1260 can be integrated with other components described herein (eg, switched mode power supplies 106 , 206 , 806 , 1206 and ion energy control component 220 ). , 820) share a common housing 1366. In this embodiment, the periodic voltage function provided to the plasma chamber 1204 may be referred to as a modified periodic voltage function because it includes a periodic voltage function modified by ion current compensation from ion current compensation component 1260 . Controller 1212 may sample voltages at different times at the electrical nodes of the output combination of switch mode power supply 1206 and ion current compensation 1260 .

As shown in FIG. 13 , an exemplary ion current compensation component 1360 is shown that includes a current source 1364 coupled to the output 1336 of the switched-mode power supply and a current source 1364 coupled to both the current source 1364 and the output 1336 . Current controller 1362. Figure 13 also shows a plasma chamber 1304 with capacitive elements C1, C2 and an ion current _II inside the plasma chamber. As shown, C1 represents the intrinsic capacitance (also referred to herein as effective capacitance) of components associated with chamber 1304 which may include, but is not limited to, insulating material, substrate, substrate support, and e-chuck, And C2 represents the sheath capacitance and stray capacitance. In this embodiment, the periodic voltage function provided to the plasma chamber 1304 and measurable at V ₀ may be referred to as a modified periodic voltage function since it includes a periodic voltage function modified by the ion current compensation Ic.

The sheath (also referred to herein as the plasma sheath) is the layer in the plasma close to the substrate surface and possibly the wall of the plasma processing chamber that has a high density of positive ions and thus an overall excess of positive charge. The surfaces that the sheath contacts typically have a predominantly negative charge. The sheath occurs by virtue of a faster electron velocity than the positive ions, thus causing a greater proportion of electrons to reach the substrate surface or wall, thus depleting the sheath of electrons. The _sheath thickness (λsheath) is a function of plasma properties such as plasma density and plasma temperature.

It should be noted that since _C1 in this embodiment is the intrinsic (herein also referred to as effective) capacitance of the components associated with chamber 1304, it is the accessible capacitance that is added to the gain control of the process. For example, some prior art approaches utilize a linear amplifier to couple a bias supply onto a substrate with a DC blocking capacitor, and then use the monitored voltage across the DC blocking capacitor as feedback to control its linear amplifier. While in many of the embodiments disclosed herein capacitors are able to couple the switched mode power supply to the substrate support, this is not necessary since several embodiments of the present invention do not require feedback control using DC blocking capacitors.

Referring to FIG. 14 in conjunction with FIG. 13 , FIG. 14 is a diagram illustrating an exemplary voltage (eg, a modified cycle voltage function) at Vo shown in FIG. 13 . In operation, the current controller 1362 monitors the voltage at Vo and calculates the ion current during interval t (as shown in FIG. 14 ) as follows:

(equation 1)

Either or both of the ion current _II and the intrinsic capacitance (also known as the effective capacitance) C ₁ may be time-varying. Since _C1 is substantially constant and measurable for a given tool, only Vo needs to be monitored to achieve uninterrupted control of the compensation current. As described above, to obtain a _{monoenergetic} distribution of more ion energies (e.g., as shown in _FIG . is related to _II according to Equation 2). In this way, a narrow spread of ion energy can be maintained even when the ion current reaches a level that affects the voltage of the substrate surface. And also, if desired, the spread of ion energy can be controlled as shown in Figures 15B and 15C such that additional ion energy is generated at the substrate surface.

Also, a feedback line 1370 is shown in Figure 13, which may be used in conjunction with controlling ion energy distribution. For example, the value of ΔV (also referred to herein as a voltage step or third portion 1406 ) shown in FIG. 14 represents instantaneous ion energy and may be used in many embodiments as part of a feedback control loop. In one embodiment, according to Equation 4, the voltage step ΔV is related to ion energy. In other embodiments, the peak-to-peak voltage V _PP may be related to the instantaneous ion energy. Alternatively, the difference between the peak-to-peak voltage V _PP and the product of the slope dV ₀ /dt of the fourth portion 1408 times the time t may be related to the instantaneous ion energy (e.g., V _PP −dV ₀ /dt·t)

Referring next to FIG. 16 , an exemplary embodiment of a current source 1664 is shown that may be used to implement the current source 1364 described with reference to FIG. 13 . In this embodiment, a controllable negative DC voltage source connected to series inductor L2 acts as a current source, but those skilled in the art will appreciate that, in light of this specification, other components and/or configurations may be used to implement current source.

Figure 43 illustrates one embodiment of a method of controlling the ion energy distribution of ions impinging on a surface of a substrate. Method 4300 begins by applying a modified periodic voltage function 4302 (see modified periodic voltage function 4402 in FIG. 44 ) to a substrate support that supports a substrate within a plasma processing chamber. The modified periodic voltage function can be controlled via at least two 'knobs', such as ion current compensation IC (see IC ₄₄₀₄ in FIG. 44 ) and supply voltage _{V PS} (see supply voltage 4406 in FIG. 44 ). For An exemplary component that generates the supply voltage is the switch-mode power supply 106 in Figure 1. To aid in explaining the supply voltage, _VPS , it is shown herein as measured without being coupled to the ion current and ion current compensation. Then the ion current compensation The modified periodic voltage function is sampled ₄₃₀₄ at the first value of IC and the second value _. At least two samples of the voltage of the modified periodic voltage function are taken for each value of ion current compensation IC. Execute Sampling 4304 to enable calculation 4306 (or determination) 4306 of ion current _II and _sheath capacitance Csheath. This determination may involve finding ion current compensation _Ic if applied to the substrate support (or when applied to the substrate support which, when applied to the substrate support, will produce a narrow (e.g., minimum) ion energy distribution function (IEDF) width. Calculation 4306 may also optionally include determining The voltage step ΔV (also referred to as the third part 1406 of the modified periodic voltage function). The voltage step ΔV can be related to the ion energy of the ions reaching the surface of the substrate. When the ion current _II is first found, it can be Neglect the voltage step ΔV. The details of sampling 4304 and calculation 4306 will be provided in the discussion of FIG. 30 below.

Once the ion current _II and the _sheath capacitance Csheath are known, method 4300 can move to method 3100 of FIG. 31 which involves setting and monitoring the ion energy and shape (eg, width) of the IEDF. For example, Figure 46 shows how changes in supply voltage can affect changes in ion energy. In particular, the shown reduced magnitude of the supply voltage results in a reduced magnitude of the ion energy. Additionally, Figure 47 shows that, given a narrow IEDF 4714, the _IEDF can be made wider by adjusting the ion current compensation IC. Alternatively or in parallel, method 4300 may perform various metrics as described with reference to FIGS. 32-41 , utilizing ion current _II , sheath capacitance _Csheath, and other aspects of the waveform of the modified periodic voltage function.

In addition to setting ion energy and/or IEDF width, method 4300 can adjust modified periodic voltage function 4308 so as to maintain ion energy and IEDF width. In particular, adjustments to the ion current compensation IC provided by the ion current compensation component and adjustments to the supply voltage can be performed ₄₃₀₈ . In some embodiments, the power supply voltage can be controlled by the bus voltage V _bus of the power supply (eg, the bus voltage V _bus of FIG. 3 ). The ion current compensation IC controls the _IEDF width, and the supply voltage controls the ion energy.

After these adjustments 4308, the modified periodic voltage function 4304 can be sampled again, and the calculation 4306 of the ion current _II , the _sheath capacitance Csheath, and the voltage step ΔV can be performed again. Ion current compensation I _C and/or supply voltage 4308 may be adjusted if ion current _II or voltage step ΔV is different from defined values (or in the alternative, desired values). A cycle of sampling 4304, calculating 4306, and adjusting 4308 may occur in order to maintain ion energy eV and/or IEDF width.

Figure 30 shows another embodiment of a method of controlling the ion energy distribution of ions impinging on a surface of a substrate. In some embodiments, as described above, it may be desirable to achieve a narrow IEDF width (eg, the minimum IEDF width, or in the alternative, ~6% full width at half maximum). As such, method 3000 may provide a modified periodic voltage function to the chamber and to the substrate support such that there is a constant substrate voltage, and thus sheath voltage, at the surface of the substrate. This in turn accelerates the ions across the sheath at a substantially constant voltage, thus enabling the ions to strike the substrate with substantially the same ion energy, which in turn provides a narrow IEDF width. For example, in FIG. 45 , it can be seen that adjusting the ion current compensation IC can cause the substrate voltage V _sub to have a constant or substantially constant voltage between pulses, thus causing a narrowing of the _IEDF .

Assuming no stray capacitance (see the last five cycles of the periodic voltage function (V ₀ ) in FIG. 45 ₎ , this modified periodic voltage function is achieved when the ion current compensation IC is equal to the ion current _II . In the alternative, the ion current compensation _I is related to the ion current I according to Equation 2, taking into account the stray capacitance _{C stray} :

(equation 2)

where C ₁ is the effective capacitance (eg, the inherent capacitance described with reference to FIGS. 3 and 13 ). The effective capacitance C ₁ can vary over time or be constant. For the purposes of this disclosure, a narrow _IEDF width may exist when I _I =IC or in the alternative when Equation 2 is satisfied. Figures 45-50 use the nomenclature I _I = _IC , but it should be understood that these equations are only a simplification of Equation 2, and that Equation 2 may therefore be substituted for the equation used in Figures 45-50. Stray capacitance _Cstray is the accumulated capacitance of the plasma chamber, as seen by the power supply. Eight cycles are shown in FIG. 45 .

Method 3000 may begin by applying a modified periodic voltage function (e.g., the modified periodic voltage function shown in FIG. The modified periodic voltage function 4402) of 3002. The voltage of the modified periodic voltage function can be sampled 3004 at two or more instants, and from the sampling, the slope dV ₀ /dt (e.g., pulse The slope between the portion or fourth portion 1408) 3006. At some point prior to decision 3010, a previously determined value of effective capacitance _C1 (e.g., intrinsic capacitance _C1 in FIG. 13 and intrinsic capacitance C10 in FIG. 3 ) may be accessed (e.g., from memory or from a user input). Take) 3008. Based on the slope dV ₀ /dt, the effective capacitance _{C 1} , and the ion current compensation IC, the function f (Equation 3 ₎ can be evaluated for each value of the ion current compensation IC as follows:

(equation 3)

If the function f is true, the ion current compensation IC is equal to the ion current _II , or in the alternative, so that Equation 2 is true, and a narrow _IEDF width 3010 has been achieved (see, eg, FIG. 45 ). If the function f is not true, the ion current compensation IC ₃₀₁₂ may be further adjusted until the function f is true. Another way of looking at this is that the ion current compensation _Ic can be adjusted until it matches the ion current _II (or in the alternative, the relationship of Equation 2 is satisfied), at which point there will be a narrow IEDF width. This adjustment of ion current compensation Ic and the resulting narrowing of the IEDF can be seen in FIG. 45 . In store operation 3014, the ion current _II and the corresponding ion current compensation Ic may be stored (eg, in a memory). The ionic current I _C can vary with time as can the effective capacitance C ₁ .

When Equation 3 is satisfied, the ion current I _I is known (either because I _C =I _I or because Equation 2 is true). Thus, method 3000 enables real-time remote and non-invasive measurement of ion current _II without affecting the plasma. This leads to several novel metrics, such as those that will be described with reference to FIGS. 32-41 (eg, remote monitoring of plasma density and remote fault detection of plasma sources).

When adjusting 3012 the compensation current I _C , the ion energy will likely be broader than the delta function, and the ion energy will be similar to that of FIG. 15B , FIG. 15C , or FIG. 44 . However, once the compensation current IC is found to satisfy Equation 2, an _IEDF will emerge, as shown in FIG. 15A or the right part of FIG. 45—as having a narrow IEDF width (eg, minimum IEDF width). This is because the voltage between pulses of the modified periodic voltage function results in a substantially constant sheath or substrate voltage when _Ic = _II (or alternatively when Equation 2 is true), and thus substantially constant ion energy. In Figure 46, the substrate voltage 4608 includes pulses between constant voltage portions. These pulses are of such short duration that their impact on the ion energy and IEDF is negligible, and thus the substrate voltage 4608 is considered substantially constant.

Further details regarding each of the method steps shown in Figure 30 are provided below. In one embodiment, the modified periodic voltage function may have a waveform like that shown in FIG. 14 and may include a first portion (e.g., first portion 1402), a second portion (e.g., 1404), a third portion (eg, third portion 1406 ) and a fourth portion (eg, fourth portion 1408 ), where the third portion may have a voltage step ΔV and the fourth portion may have a slope dV ₀ /dt. The slope dV ₀ /dt can be positive, negative or zero. The modified periodic voltage function 1400 can also be described as having pulses comprising a first portion 1402, a second portion 1404, and a third portion 1406, with a portion between the pulses (fourth portion 1408).

The modified periodic voltage function may be measured as V ₀ in FIG. 3 and may appear as modified periodic voltage function 4402 in FIG. 44 . Modified periodic voltage function 4402 is produced by combining supply voltage 4406 (also referred to as periodic voltage function) with ion current compensation 4404 . The supply voltage 4406 is primarily responsible for generating and shaping the pulses of the modified periodic voltage function 4402, and the ion current compensation 4404 is primarily responsible for generating and shaping the portion between pulses, which is typically a linearly sloped voltage. Increasing the ion current compensation Ic results in a decrease in the magnitude of the slope of the portion between pulses, as seen in FIG. 45 . Reducing the magnitude of the supply voltage 4606 results in a reduction in the magnitude of the amplitude of the pulses and the peak-to-peak voltage of the modified periodic voltage function 4602 , as seen in FIG. 46 .

In case the power supply is a switch mode power supply, a switching diagram 4410 of the first switch T1 and the second switch T2 may be applied. For example, the first switch T1 may be implemented as the switch T1 in FIG. 3 , and the second switch T2 may be implemented as the second switch T2 in FIG. 3 . Both switches are shown to have exactly the same switching times, but are 180° out of phase. In other embodiments, the switches may have a slight phase offset such as that shown in FIG. 4 . When the first switch T1 is turned on, the supply voltage pulls to a maximum magnitude, which is negative in FIG. 44 because the supply has a negative bus voltage. The second switch T2 is closed during this period, so that the supply voltage 4406 is isolated from ground. When the switch is reversed, the supply voltage 4406 approaches and passes slightly over ground. In the illustrated embodiment, there are two pulse widths, but this is not required. In other embodiments, the pulse width may be exactly the same for all periods. In other embodiments, the pulse width can be varied or modulated in time.

The modified periodic voltage function may be applied to the substrate support 3002 and sampled 3004 as V _at the last accessible point before the modified periodic voltage function reaches the substrate support (e.g., in a switched-mode power supply with effective capacitance). The unmodified periodic voltage function (or supply voltage 4406 in FIG. 44 ) may be derived from a power supply such as switched mode power supply 1206 in FIG. 12 . Ion current compensation 4404 in FIG. 44 may originate from a current source such as ion current compensation component 1260 in FIG. 12 or ion current compensation component 1360 in FIG. 13 .

A portion of the modified periodic voltage function or the entire modified periodic voltage function may be sampled 3004 . For example, a fourth portion (eg, fourth portion 1408) may be sampled. Sampling 3004 can be performed between the power supply and the substrate support. For example, in FIG. 1 , sampling 3004 may be performed between switched mode power supply 106 and support 108 . For example, in FIG. 1 , sampling 3004 may be performed between switched mode power supply 106 and support 108 . In FIG. 3, sampling 3004 may be performed between inductor L1 and inherent capacitance C10. In one embodiment, sampling 3004 may be performed at _V0 between capacitance C3 and intrinsic capacitance C10. Since the intrinsic capacitance C10 and the elements representing the plasma (R2, R3, C1 and C2) are not accessible for real-time measurements, sampling 3004 is typically performed to the left of the intrinsic capacitance C10 in FIG. 3 . Although the intrinsic capacitance C10 is not usually measured during processing, it is usually known to be constant and thus can be set during manufacture. Meanwhile, in some cases, the inherent capacitance C10 may vary with time.

While in some embodiments only two samples of the modified periodic voltage function are required, in other embodiments hundreds, thousands or thousands of samples may be chosen for each cycle of the modified periodic voltage function samples. For example, the sampling rate may be greater than 400kHz. These sampling rates enable more accurate and detailed monitoring of the modified periodic voltage function and its shape. In this same vein, more detailed monitoring of the cycle voltage function allows for a more precise comparison of waveforms: between different cycles, between different process conditions, between different processes, between different chambers, between different sources Wait. For example, at these sampling rates, the first, second, third and fourth parts 1402, 1404, 1406, 1408 of the periodic voltage function shown in Figure 14 can be distinguished, which would not be possible at conventional sampling rates. In some embodiments, the higher sampling rate enables resolution of the voltage step ΔV and slope dV ₀ /dt, which is not possible in the art. In some embodiments, a portion of the modified periodic voltage function may be sampled while other portions are not sampled.

The slope dV ₀ /dt may be calculated 3006 based on a number of V ₀ measurements taken during time t (eg, fourth portion 1408 ). For example, a linear fit can be performed to fit a line to the V ₀ value, where the slope of the line gives the slope dV _o /dt. In another example, values of V _at the beginning and end of time t (e.g., fourth portion 1408) in FIG. 14 can be determined, and a line can be fitted between these two points, wherein the The slope of the line is given as dV _o /dt. These are just two of many ways in which the slope dV _o /dt of the portion between pulses can be calculated.

Decision 3010 may be part of an iterative loop for tuning the IEDF to a narrow width (eg, the minimum width, or in the alternative, 6% full width at half maximum). Equation 3 holds true only if the ion current compensation I is equal to the ion current _I (or in the alternative, related to _I according to Equation 2), which is only true if there is a constant substrate voltage and thus constant and substantially Occurs in the case of upper single ion energies (narrow IEDF width). A constant substrate voltage 4608 (V _sub ) is seen in FIG. 46 . Therefore, ion current _II or alternatively ion current compensation Ic may be used in Equation 3.

Alternatively, two values along the fourth portion 1408 (also referred to as the portion between pulses) may be sampled for the first period and the second period, and the first slope and the second slope may be determined for each period, respectively. slope. From these two slopes, the ion current compensation Ic can be determined, which is expected to make Equation 3 true for the third (but not yet measured) slope. Therefore, the ion current _II can be estimated, which is expected to correspond to a narrow _IEDF width. These are just two of many ways in which a narrow IEDF width can be determined and a corresponding ion current compensation _Ic and/or a corresponding ion current II can be found.

Adjustment 3012 of ion current compensation Ic may involve increasing or decreasing ion current compensation Ic, and there is no limit to the step size of each adjustment. In some embodiments, the sign of the function f in Equation 3 can be used to determine whether to increase or decrease ion current compensation. If the sign is negative, the ion current compensation Ic may be decreased, while a positive sign may indicate that the ion current compensation Ic needs to be increased.

Once the ion current compensation Ic has been identified to be equal to the ion current _II (or in other schemes related thereto according to Equation 2), the method 3000 can proceed to further setpoint operations (see FIG. 31 ) or remote chamber and source monitoring operations ( See Figures 32-41). The further set point operations may include setting the ion energy (see also FIG. 46 ) and the distribution or IEDF width of the ion energy (see also FIG. 47 ). Source and chamber monitoring may include monitoring plasma density, source supply anomalies, plasma arcing, and others.

Furthermore, method 3000 optionally loops back to sampling 3004 to continuously (or, in the alternative, periodically) update ion current compensation Ic. For example, sampling 3004, calculating 3006, deciding 3010, and adjusting 3012 may be performed periodically to ensure that Equation 3 continues to be satisfied, taking into account the current ion current compensation Ic. At the same time, if the ion current compensation Ic satisfying Equation 3 is updated, the ion current _II may also be updated and the updated value may be stored 3014 .

While method 3000 may find and set ion current offset Ic to equal ion current _II , or in the alternative, satisfy Equation 2, without setting ion current _Ic to this value (or in alternative , before setting the ion current IC to this value), the value of the ion current compensation _Ic required to achieve a narrow IEDF width can be determined. For example, by applying a first ion current for the first period compensating for Ic1 and measuring the _first slope _dV01 /dt of the voltage between pulses, and by applying a second ion current for a _second period Ic2 and measuring between pulses The second slope dV ₀₂ /dt of the voltage of , may determine the third slope dV ₀₃ /dt associated with the third ion current compensation Ic ₃ , where Equation 3 is expected to be true. The third ion current compensation Ic ₃ may be an ion current compensation which if applied would result in a narrow IEDF width. Therefore, the ion current compensation _Ic satisfying Equation 3 and thus corresponding to the ion current II can be determined by means of only a single adjustment of the ion current compensation. Method 3000 may then move to the method described in FIG. 31 and/or FIGS. 32-41 without ever setting ion current _Ic to the value required to achieve a narrow IEDF width. Such an embodiment may be implemented in order to increase tuning speed.

Figure 31 shows a method for setting the IEDF width and ion energy. The method is derived from the method 3000 shown in FIG. 30 and can take either of the left path 3100 (also known as the IEDF branch) or the right path 3101 (also known as the ion energy branch) , which need to set the IEDF width and ion energy separately. The ion energy eV is proportional to the voltage step ΔV or the third part 1406 of the modified periodic voltage function 1400 of FIG. 14 . The relationship between ion energy eV and voltage step ΔV can be written as Equation 4:

(equation 4)

where _C1 is the effective capacitance (e.g., chuck capacitance; intrinsic capacitance C10 in Figure 3; or intrinsic capacitance C1 in Figure 13), and _C2 is the sheath capacitance (e.g., sheath capacitance C4 in Figure 3 or Sheath capacitance C2) in Figure 3). The sheath capacitance C ₂ may include stray capacitance and depends on the ion current I _I . The voltage step ΔV may be measured as a change in voltage between the second portion 1404 and the fourth portion 1408 of the modified periodic voltage function 1400 . By controlling and monitoring the voltage step ΔV, which is a function of the supply voltage or a bus voltage such as the bus voltage V _bus in FIG. 3 , the ion energy eV can be controlled and known.

Meanwhile, the IEDF width can be estimated according to Equation 5:

(equation 5)

where I is II in the case where C is C in _series , or _I is IC in the case where C is _C in _effect . Time t is the time between pulses, V _PP is the peak-to-peak voltage, and ΔV is the voltage step.

In addition, the sheath capacitance _C2 can be used in various computing and monitoring operations. For example, the Debye _sheath distance λsheath can be estimated as follows:

(equation 6)

where is the vacuum permittivity, and A is the area of the substrate (or in the alternative, the surface area of the substrate support). In some high voltage applications, Equation 6 is written as Equation 7:

(Equation 7)

Additionally, the e-field in the sheath can be estimated as a function of the sheath capacitance C ₂ , the sheath distance λ _sheath and the ion energy eV. The sheath capacitance C ₂ together with the ion current _II can also be used to determine the plasma density _ne according to Equation 8, where the saturation current I _sat is linearly related to the compensation current I _C for a separately ionized plasma.

(Equation 8)

The effective mass of ions at the substrate surface can be calculated using the sheath capacitance C ₂ and the saturation current I _sat . The plasma density _ne , the electric field in the sheath, the ion energy eV, the effective mass of the ion and the DC potential V _DC of the substrate are fundamental plasma parameters that are usually only monitored via indirect means in the art. The present disclosure enables direct measurement of these parameters, thus enabling more accurate real-time monitoring of plasma properties.

As seen in Equation 4, the sheath capacitance C ₂ can also be used to monitor and control the ion energy eV, as shown in ion energy branch 3101 of FIG. 31 . The ion energy branch 3101 begins by receiving a user selection 3102 of ion energy. The ion energy branch 3101 may then set 3104 the initial supply voltage of the switched mode power supply supplying a periodic voltage function. At some point prior to the sampled cycle voltage operation 3108, the ion current 3106 may also be accessed (eg, from memory). The periodic voltage can be sampled 3108 and a measurement of a third portion of the modified periodic voltage function can be measured 3110 . Ion energy I _I 3112 may be calculated from the voltage step ΔV (also referred to as the third portion (eg, third portion 1406 )) of the modified periodic voltage function. The ion energy branch 3101 can then determine if the ion energy is equal to the defined ion energy 3114, and if so, the ion energy is at the desired set point and the ion energy branch 3101 can end. If the ion energy is not equal to the defined ion energy, the ion energy branch 3101 can adjust the supply voltage 3116 and sample the cycle voltage again 3108 . The ion energy branch 3101 may then loop through sampling 3108, measuring 3110, calculating 3112, deciding 3114, and setting 3116 until the ion energy is equal to the defined ion energy.

A method for monitoring and controlling the IEDF width is shown in IEDF branch 3100 of FIG. 31 . The IEDF branch 3100 includes receiving a user selection 3150 of an IEDF width and sampling 3152 a current IEDF width. Decision 3154 then determines whether the defined IEDF width is equal to the current IEDF width, and if decision 3152 is satisfied, the IEDF width is as expected (or as defined) and the IEDF branch 3100 may end. However, if the current IEDF width is not equal to the defined IEDF width, the ion current compensation Ic 3156 may be adjusted. This determination 3154 and adjustment 3156 may continue in a loop until the current IEDF width is equal to the defined IEDF width.

In some embodiments, IEDF branch 3100 may also be implemented to preserve the desired IEDF shape. Various IEDF shapes can be generated, and each IEDF shape can be associated with a different ion energy and IEDF width. For example, the first IEDF shape may be a delta function, while the second IEDF shape may be a square function. Other IEDF shapes may be cup-shaped. Examples of various IEDF shapes can be seen in FIG. 11 .

Knowing the ion current _II and the voltage step ΔV, Equation 4 can be solved for the ion energy eV. The voltage step ΔV can be controlled by varying the supply voltage, which in turn causes the voltage step ΔV to vary. A larger supply voltage results in an increase in the voltage step ΔV, and a decrease in the supply voltage results in a decrease in the voltage step ΔV. In other words, increasing the supply voltage results in larger ion energies eV.

Furthermore, because the above systems and methods operate on a continuously varying feedback loop, desired (or defined) ion can be maintained despite variations in the plasma due to changes in plasma source or chamber conditions or deliberate adjustments. Energy and IEDF width.

Although Figures 30-41 have been described in terms of a single ion energy, those skilled in the art will recognize that these methods of generating and monitoring a desired (or defined) IEDF width (or IEDF shape) and ion energy can be further utilized For generating and monitoring two or more ion energies, each ion energy has its own IEDF width (or IEDF shape). For example, by providing the first power supply voltage V _PS in the first, third and fifth periods and the second power supply voltage in the second, fourth and sixth periods, two can be achieved for ions reaching the surface of the substrate. different and narrow ion energies (eg, Figure 42A). Using three different supply voltages resulted in three different ion energies (eg, Figure 42B). By varying the time during which each of multiple supply voltages is applied, or the number of cycles during which each supply voltage level is applied, ion flux for different ion energies can be controlled (e.g., FIG. 42C ).

The above discussion has shown how combining the periodic voltage function provided by the power supply with the ion current compensation provided by the ion current compensation component can be used to control the ion energy as well as the IEDF width and/or IEDF shape.

Some of the controls described so far are achieved by using some combination of: (1) a fixed waveform (sequential periods of the waveform are the same); (2) a waveform with at least two sections that are the same as Ion energy is proportional to the IEDF (e.g., the third and fourth portions 1406 and 1408 shown in FIG. 14); and (3) a high sampling rate (e.g., 125 MHz), which enables precise monitoring of different features of the waveform . For example, in the case of prior art techniques such as linear amplifiers sending a waveform to the substrate that resembles a modified periodic voltage function, the undesired variation between cycles makes it difficult to use those prior art waveforms to characterize ion energy or IEDF width (or IEDF shape).

Where linear amplifiers have been used to bias the substrate support, the need for sampling at high rates has not been seen because the waveform is not consistent from cycle to cycle, and thus the analytical characteristics of the waveform (e.g., the interval between pulses part of the slope) will generally not be informative. This useful information does appear when fixed waveforms are used, as seen in this and related disclosures.

The fixed waveforms and high sampling rates disclosed herein further lead to more precise statistical observations being feasible. Due to this increased precision, the operating and processing characteristics of the plasma source and the plasma in the chamber can be monitored via monitoring various characteristics of the modified periodic voltage function. For example, measurement of the modified periodic voltage function enables remote monitoring of sheath capacitance and ion current, and can be done without knowledge of chamber process or other chamber details. The several examples that follow illustrate only some of the numerous ways in which the systems and methods described thus far can be used for non-intrusive monitoring and fault detection of sources and chambers.

As an example of monitoring, and with reference to FIG. 14 , a DC offset of waveform 1400 may indicate the health of a plasma source (hereinafter "source"). In another example, the slope of the top portion 1404 (second portion) of the pulse of the modified periodic voltage function may be associated with a damping effect within the source. The standard deviation from the slope of the top portion 1404 of the horizontal (shown as having a slope equal to 0) is another way to monitor source health based on aspects of the waveform 1400 . Another aspect involves measuring the standard deviation of the sampled V ₀ points along the fourth portion 1408 of the modified periodic voltage function, and correlating the standard deviation to the chamber ringing. For example, where this standard deviation is monitored among successive pulses and increases over time, this may indicate the presence of ringing in the chamber, such as in an e-chuck. Ringing can be a sign of a poor electrical connection to or in the chamber or of additional unwanted inductance or capacitance.

Figure 32 shows two modified periodic voltage functions delivered to the substrate support according to one embodiment of the present disclosure. When compared, the two modified periodic voltage functions can be used for chamber matching or in situ anomaly or fault detection. For example, one of the two modified periodic voltage functions may be a reference waveform, and the second modified periodic voltage function may be selected from the plasma processing chamber during calibration. The difference between the two modified periodic voltage functions (eg, the difference in peak-to-peak voltage V _PP ) can be used to calibrate the plasma processing chamber. Alternatively, the second modified periodic voltage function may be compared to a reference waveform during processing, and any difference (e.g., shift) in waveform characteristics may indicate a fault (e.g., a fourth portion 3202 of the modified periodic voltage function difference in slope).

Figure 33 shows ion current waveforms that may indicate plasma source instabilities or changes in plasma density. Fluctuations in ion current _II , such as those shown in Figure 33, can be analyzed to identify faults and anomalies in the system. For example, periodic fluctuations in FIG. 33 may indicate low frequency instabilities in the plasma source (eg, plasma power supply 102). Such fluctuations in ion current _II can also indicate cyclic changes in plasma density. This indicator and the possible faults or abnormalities it may indicate are but one of many ways in which remote monitoring of the ion current _II can be used to particular advantage.

Figure 34 shows the ion current _II as a function of the modified periodic voltage with a non-periodic shape. This example of ion current _II can be indicative of non-periodic fluctuations such as plasma instabilities and changes in plasma density. Such fluctuations may also indicate various plasma instabilities, such as arcing, formation of parasitic plasma, or drift in plasma density.

Figure 35 shows a modified cycle voltage function that may indicate a fault within the bias supply. The top portion of the third illustrated cycle (also referred to herein as the second portion) shows anomalous behavior that may indicate ringing in the bias power supply (eg, power supply 1206 in FIG. 12 ). This ringing may be an indication of a fault within the bias supply. Further analysis of the ringing can identify characteristics that help identify faults within the power system.

Figure 36 shows a modified periodic voltage function that can indicate dynamic (or non-linear) changes in the capacitance of the system. For example, stray capacitances that are nonlinearly voltage dependent can lead to such a modified periodic voltage function. In another example, plasma breakdown or a fault in the chuck may also result in such a modified periodic voltage function. In each of the three illustrated cycles, non-linearity in the fourth portion 3602 of each cycle may indicate dynamic changes in system capacitance. For example, non-linearity may indicate a change in the sheath capacitance since other components of the system capacitance are mostly fixed.

Figure 37 shows a modified periodic voltage function indicative of a change in plasma density. The shown modified periodic voltage function shows a monotonic shift in slope dV ₀ /dt, which may be indicative of a change in plasma density. These monotonic movements can provide a direct indication of expected events, such as the end point of process etch. In other embodiments, these monotonic movements may indicate failures in the process where expected events do not exist.

Figure 38 shows sampling of ion current for different process runs, where drift in ion current may indicate system drift. Each data point may represent the ion current for a given run, where acceptable limits are user-defined or automatic limits that define acceptable ion currents. A drift in the ion current, which gradually pushes the ion current above the acceptable limit, may indicate that substrate damage is possible. This type of monitoring can also be combined with any number of other traditional monitoring (such as optical omission, thickness measurement, etc.). These traditional types of monitoring in addition to monitoring ion current drift can augment existing monitoring and statistical controls.

Figure 39 shows sampling of ion current for different process parameters. In this illustration, the ion current can be used as a figure of merit to differentiate between different processes and different process characteristics. Such data can be used in the development of plasma formulations and processes. For example, eleven process conditions may be tested, resulting in the eleven shown ionic current data points, and the process producing the preferred ionic current may be selected as the ideal process, or as the preferred process in the alternative. For example, the lowest ionic current can be selected as the ideal process, and thereafter the ionic current associated with the preferred process can be used as a metric to determine whether the process is performing with the preferred process conditions. This figure of merit can be used to name some non-limiting sexual example.

Figure 40 shows two modified periodic voltage functions monitored without plasma in the chamber. These two modified periodic voltage functions can be compared and used to characterize the plasma chamber. In an embodiment, the first modified periodic voltage function may be a reference waveform and the second modified periodic voltage function may be a currently monitored waveform. These waveforms can be chosen in the absence of plasma in the processing chamber (e.g., after chamber cleaning or preventive maintenance), and thus a second waveform can be used to provide insight into the chamber before releasing it into (or back into) production. Verification of electrical status.

Figure 41 shows two modified periodic voltage functions that can be used to verify the plasma process. The first modified periodic voltage function may be a reference waveform and the second modified periodic voltage function may be a currently monitored waveform. The currently monitored waveform may be compared to a reference waveform, and any differences may indicate parasitic and/or non-capacitive impedance issues that would otherwise be undetectable using traditional monitoring methods. For example, ringing seen on the waveform of Figure 35 can be detected and can indicate ringing in the power supply.

Any of the metrics shown in FIGS. 32-41 may be monitored while method 3000 loops to update ion current compensation Ic, ion current _II , and/or sheath capacitance _Csheath . For example, after each ion current _II , a sample is taken in FIG. 38, method 3000 may loop back to sample 3004 to determine an updated ion current _II . In another example, corrections to ion current _II , ion energy eV, or IEDF width may be desired as a result of monitoring operations. Corresponding corrections can be made, and method 3000 can loop back to sampling 3004 to find a new ion current compensation Ic that satisfies Equation 3.

Those skilled in the art will appreciate that the methods shown in FIGS. 30 , 31 , and 43 do not require any particular or described order of operations, nor are they limited to any order shown or implied by the figures. For example, metrics may be monitored before, during, or after setting and monitoring the IEDF width and/or ion energy eV (FIGS. 32-41).

Figure 44 shows various waveforms at different points in the system disclosed herein. Consider the illustrated switching pattern 4410 of the switching components of the switch mode power supply, the supply voltage V _PS 4406 (also referred to herein as the periodic voltage function), the ion current compensation Ic 4404, the modified periodic voltage function 4402 and the substrate At voltage V _sub 4412 , the IEDF has a width 4414 as shown (which may not be drawn to scale) or an IEDF shape 4414 . This width is wider than what this disclosure has referred to as a "narrow width". As can be seen, the substrate voltage V _sub 4412 is not constant when the ion current compensation _Ic 4404 is greater than the ion current II. The IEDF width 4414 is proportional to the voltage difference between ramp portions between pulses of the substrate voltage V _sub 4412 .

With this non-narrow IEDF width 4414 in mind, the methods disclosed herein require adjusting the ion current compensation Ic until _Ic = _II (or in the alternative, related to _II according to Equation 2). Figure 45 shows the effect of making a final incremental change in ion current compensation Ic so that it matches ion current _II . When I _C = _II , the substrate voltage V _sub 4512 becomes substantially constant and the IEDF width 4514 changes from non-narrow to narrow.

Once the narrow IEDF has been achieved, the ion energy can be adjusted to a desired or defined value as shown in FIG. 46 . Here, the magnitude of the supply voltage (or, in the alternative, the bus voltage V _bus of the switched-mode power supply) is reduced (eg, the maximum negative amplitude of the supply voltage 4606 pulses is reduced). Thus, ΔV ₁ decreases to ΔV ₂ , as does the peak-to-peak voltage, as it decreases from V _PP1 to V _PP2 . The magnitude of the substantially constant substrate voltage _Vsub 4608 is correspondingly reduced, thus reducing the magnitude of the ion energy from 4615 to 4614 while maintaining a narrow IEDF width.

Whether or not the ion energy is tuned, the IEDF width can be widened after achieving a narrow IEDF width, as shown in FIG. 47 . Here, assuming I _I = I _C (or in the alternative, Equation 2 gives the relationship between I _I and I _C ), I _C can be adjusted, thus changing the pulse-to-pulse ratio of the modified periodic voltage function 4702. The slope of the part. Since the ion current compensation Ic and the ion current _II are not equal, the substrate voltage moves from substantially constant to non-constant. A further consequence is that IEDF width 4714 extends from narrow IEDF 4714 to non-narrow IEDF 4702 . The farther I _I is adjusted from I _C , the wider the IEDF 4714 width will be.

Figure 48 shows one pattern of supply voltages that can be used to achieve more than one ion energy level, where each ion energy level has a narrow IEDF 4814 width. The magnitude of the supply voltage 4806 alternates every cycle. This produces an alternating ΔV and peak-to-peak voltage for each cycle in the modified cycle voltage function 4802 . The substrate voltage 4812 in turn has two substantially constant voltages that alternate between pulses of the substrate voltage. This produces two different ion energies, each with a narrow IEDF 4814 width.

Figure 49 shows another mode of supply voltage that can be used to achieve more than one ion energy level, where each ion energy level has a narrow IEDF 4914 width. Here, supply voltage 4906 alternates between two different magnitudes, but also alternates two cycles at a time before the alternation. As can be seen, the average ion energy is the same as if the VPS ₄₉₀₆ alternated every cycle. This shows just one example of how various other modes of VPS ₄₉₀₆ can be used to achieve the same ion energy.

Figure 50 shows one combination of supply voltage V _PS 5006 and ion current compensation Ic 5004 that can be used to create the defined IEDF 5014. Here, the alternating supply voltage 5006 produces two different ion energies. Additionally, by adjusting the ion current compensation 5004 away from the ion current _II , the IEDF 5014 width per ion energy can be extended. If the ion energies are close enough, as they are in the illustrated embodiment, the IEDFs 5014 for the two ion energies will overlap, resulting in one large IEDF 5014 . Other variations are possible, but this example is intended to show how a combination of adjustments to V _PS 5006 and IC 5004 can be used to achieve a defined ion energy and a defined _IEDF 5014 .

Referring next to Figures 17A and 17B, block diagrams illustrating other embodiments of the present invention are shown. As shown, the substrate support 1708 in these embodiments includes an electrostatic chuck 1782 and an electrostatic chuck power supply 1780 is used to provide power to the electrostatic chuck 1782 . In some variations, the electrostatic chuck power supply 1780 is arranged to provide power directly to the substrate support 1708, as shown in FIG. 17A, and in other variations, the electrostatic chuck power supply 1780 is arranged to provide power in conjunction with a switch mode power supply. It should be noted that the tandem chuck can be powered by an independent power source or through the use of a controller for net DC chuck functionality. In this DC coupled (eg, no DC blocking capacitor) series chuck function, undesired interference with other RF sources can be minimized.

Figure 18 shows a block diagram illustrating yet another embodiment of the present invention where the plasma power supply 1884 typically used to generate the plasma density is also configured to drive the substrate support 1808 and electrostatic chuck next to the switched mode power supply 1806 Power 1880. In this embodiment, each of the plasma power supply 1884, electrostatic chuck power supply 1880, and switch mode power supply 1806 may be located in separate components, or two or more of the power supplies 1806, 1880, 1884 may be configured as in the same physical assembly. Advantageously, the embodiment shown in FIG. 18 enables the top electrode 1886 (eg, showerhead) to be electrically grounded to achieve electrical symmetry and reduce the level of damage due to a small number of arcing events.

Referring to Figure 19, there is shown a block diagram illustrating yet another embodiment of the present invention. As shown, the switch mode power supply 1906 in this embodiment is configured to provide power to the substrate support and chamber 1904 in order to both bias the substrate and ignite (and sustain) the plasma without additional plasma Bulk Power Supply (eg, without plasma power supply 102, 202, 1202, 1702, 1884) For example, switch mode power supply 1806 may be operated at a duty cycle sufficient to ignite and sustain the plasma while providing bias to the substrate support.

Reference is next made to FIG. 20 , which is a block diagram illustrating input parameters and control outputs of a control section that may be used in conjunction with the embodiments described with reference to FIGS. 1 to 19 . The illustration of the controls is intended to provide a simplified illustration of exemplary control inputs and outputs that may be used in conjunction with the embodiments described herein, and is not intended to be a hardware diagram. In an actual implementation, the illustrated control portion may be distributed among several discrete components, which may be implemented by hardware, software, firmware, or combinations thereof.

With reference to the foregoing embodiments herein, the controller shown in FIG. 20 may provide the controller 112 described with reference to FIG. 1 , the controller 212 and the ion energy control unit 220 described with reference to FIG. The ion energy control part 820, the ion current compensation part 1260 described with reference to FIG. 12, the current controller 1362 described with reference to FIG. 13, the Icc control shown in FIG. 16, the controllers 1712A and 1712B shown in FIGS. 18 and 19 illustrate the functionality of one or more of the controllers 1812 and 1912, respectively.

As shown, parameters that may be used as input to the control section include dVo/dt and ΔV which have been described in more detail with reference to FIGS. 13 and 14 . As described above, dVo/dt can be used in conjunction with the ion energy distribution expansion input ΔE to provide a control signal Icc that controls the width of the ion energy distribution expansion described with reference to FIGS. 12, 13, 14, 15A-C and FIG. Additionally, the ion energy control input (Ei) in combination with optional feedback ΔV can be used to generate an ion energy control signal (e.g., affect Vbus shown in FIG. 3 ) to achieve the desired (defined ) ion energy distribution. And another parameter that can be incorporated into many e-chuck embodiments is a DC offset input that provides electrostatic force to hold the wafer on the chuck for effective thermal control.

FIG. 21 illustrates a plasma processing system 2100 according to an embodiment of the disclosure. The system 2100 includes a plasma processing chamber 2102 that encloses a plasma 2104 for etching a top surface 2118 of a substrate 2106 (and other plasma processes). A plasma is generated (eg, in situ or remote or projected) by a plasma source 2112 powered by a plasma power supply 2122 . The plasma _sheath voltage Vsheath measured between the plasma 2104 and the top surface 2118 of the substrate 2106 accelerates ions from the plasma 2104 across the plasma sheath 2115, causing the accelerated ions to impact the top of the substrate 2106 Surface 2118 and substrate 2106 (or portions of substrate 2106 not protected by photoresist) are etched. Plasma 2104 is at plasma potential _V3 with respect to ground (eg, a wall of plasma processing chamber 2102). Substrate 2106 has a bottom surface 2120 that is electrostatically held to support 2108 via electrostatic chuck 2111 and a chuck potential V _Chuck between top surface 2121 of electrostatic chuck 2111 and substrate 2106 . Substrate 2106 is a dielectric, and thus may have a first potential V ₁ at top surface 2118 and a second potential V ₂ at bottom surface 2120 . The top surface of the electrostatic chuck 2121 is in contact with the bottom surface 2120 of the substrate, and thus _both surfaces 2120, 2121 are at the same potential V2. The first potential V ₁ , the chuck potential V _chuck and the second potential V ₂ are controlled via an AC waveform with a DC bias or offset generated by the switch mode power supply 2130 and provided to the electrostatic chuck via the first conductor 2124 2111. Optionally, an AC waveform is provided via a first conductor 2124 and a DC waveform is provided via an optional second conductor 2125 . The AC and DC outputs of the switch mode power supply 2130 can be controlled via a controller 2132 which is also configured to control various aspects of the switch mode power supply 2130 .

The ion energy and ion energy distribution are functions of the first potential V ₁ . Switched mode power supply 2130 provides an AC waveform tailored to affect a desired first potential V ₁ that is known to produce _a desired (or defined) ion energy and ion energy distribution. The AC waveform may be RF and have a non-sinusoidal waveform such as shown in Figures 5, 6, 11, 14, 15a, 15b and 15c. The first potential V ₁ may be proportional to a change in the voltage ΔV shown in FIG. 14 . The _first potential V1 is also equal to the plasma voltage _V3 minus the plasma sheath voltage _Vsheath . But since the plasma voltage _V3 is usually small (for example, less than 20V) compared to the plasma sheath voltage _Vsheath (for example, 50V–2000V), the _first potential V1 and the plasma sheath voltage _Vsheath The _layers are approximately equal and may be considered equal for implementation purposes. Thus, since the plasma sheath voltage _{Vsheath is} indicative of ion energy, the first potential V ₁ is proportional to the ion energy distribution. By maintaining a constant first potential V ₁ , the plasma sheath voltage _{Vsheath is} constant, and thus substantially all ions are accelerated via the same energy, and thus a narrow ion energy distribution is achieved. Plasma voltage V ₃ results from energy imparted to plasma 2104 via plasma source 2112 .

A first potential V ₁ at the top surface 2118 of the substrate 2106 is developed via a combination of capacitive charging from the electrostatic chuck 2111 and charge accumulation from electrons and ions passing through the sheath 2115 . The AC waveform from the switch mode power supply 2130 is tailored to counteract the effects of ion and electron transfer through the sheath 2115 and the resulting charge accumulation at the top surface 2118 of the substrate 2106 such that the _first potential V remains substantially constant.

The chuck force holding the substrate 2106 to the electrostatic chuck 2111 is a function of the _chuck potential VCHHuck. The switch mode power supply 2130 provides a DC bias or DC offset to the AC waveform such that the _second potential V2 is at _a different potential than the first potential V1. This potential difference results in a _chuck voltage VCHHuck. The chuck voltage VCHUCK can be measured from the top surface 2221 of the electrostatic _chuck 2111 to a reference layer inside the substrate 2106, which includes the inside of the substrate except the bottom surface 2120 of the substrate 2106 (the reference layer is on the substrate 2106). Any elevation other than the exact location within 2106 may vary). Thus, the chuck is controlled by and proportional to the _second potential _V2 .

In an embodiment, the _second potential V is equal to the DC offset of the switch mode power supply 2130 modified by the AC waveform (in other words, an AC waveform with a DC offset, wherein the DC offset is greater than the peak-to-peak voltage of the AC waveform). The DC offset may be substantially larger than the AC waveform such that the DC component of the output of the switch mode power supply 2130 dominates the second potential V ₂ and the AC component is negligible or disregarded.

The potential within the substrate 2106 varies between first and second potentials V ₁ , V ₂ . Due to the presence of Coulomb attraction between the substrate 2106 and the electrostatic chuck 2111, the chuck potential V _chuck can be positive or negative (e.g., V ₁ >V ₂ or V ₁ < V ₂ ), regardless of the chuck potential V _chuck What is the polarity of the _disk .

The switch mode power supply 2130 in conjunction with the controller 2132 can deterministically and sensorlessly monitor various voltages. In particular, ion energy (eg, mean energy and ion energy distribution) is deterministically monitored based on parameters of the AC waveform (eg, slope and step). For example, plasma voltage V ₃ , ion energy, and ion energy distribution are proportional to parameters of the AC waveform generated by switch mode power supply 2130 . In particular, ΔV of the falling edge of the AC waveform (see eg FIG. 14 ) is proportional to the first potential V ₁ , and thus proportional to the ion energy. By keeping the _first potential V1 constant, the ion energy distribution can be kept narrow.

While the _first potential V cannot be measured directly and the correlation between the output of the switch-mode power supply and the _first voltage V can vary based on the capacitance of the substrate 2106 and processing parameters, it can be determined empirically after a short processing time has elapsed The constant of proportionality between ΔV and the _first potential V1. For example, where the falling edge ΔV of the AC waveform is 50V and the constant of proportionality is empirically found to be 2 for a given substrate and process, the first potential V ₁ may be expected to be 100V. The ratio between the step voltage ΔV and the first potential V ₁ (and thus also the ion energy eV) is described by Equation 4. Thus, the first potential V ₁ as well as the ion energy and ion energy distribution can be determined without any sensors inside the plasma processing chamber 2102 based on knowledge of the AC waveform of the switched mode power supply. Additionally, the switch mode power supply 2130 in conjunction with the controller 2132 can monitor when and if chucking occurs (eg, whether the substrate 2106 is held to the electrostatic _chuck 2111 via the chuck potential VCHHuck).

Dechucking is performed by eliminating or reducing the _chuck potential VCHuck. This can be done by setting the _second potential V2 equal to the _first potential V1. In other words, the DC offset and AC waveform can be adjusted so as to result in the chuck voltage V _chuck being close to 0V. Compared to conventional dechucking methods, the system 2100 achieves faster dechucking and thus greater throughput because both the DC offset and the AC waveform can be adjusted to achieve dechucking. Also, when the DC and AC power sources are in a switch mode power supply 2130, their circuits are more unified and closer together, can be controlled via a single controller 2132 (as compared to a typical parallel setup of DC and AC power sources), and Change output faster. The speed of dechucking achieved by embodiments disclosed herein also enables dechucking after the plasma 2104 is extinguished, or at least after power from the plasma source 2112 has been turned off.

Plasma source 2112 may take a variety of forms. For example, in an embodiment, plasma source 2112 includes electrodes inside plasma processing chamber 2102 that establish an RF field within chamber 2102 that ignites and maintains plasma 2104 . In another embodiment, the plasma source 2112 includes a remotely projected plasma source that remotely generates an ionizing electromagnetic field, projects or extends the ionizing electromagnetic field into the processing chamber 2102, and uses the ionizing electromagnetic field to ignite and maintain Plasma2104. However, the remotely projected plasma source also includes a field delivery portion (e.g., a conductive tube) through which the ionizing electromagnetic field passes on its way to the plasma processing chamber 2102, during which time the ionizing electromagnetic field decays such that the plasma processing chamber 2102 The field strength is only one-tenth, one-hundredth, one-thousandth or even a smaller fraction of the field strength when said field was first generated in the remote projection plasma source. Plasma source 2112 is not drawn to scale.

The switched mode power supply 2130 can be floating and thus can be biased with any DC offset by a DC power supply (not shown) connected in series between ground and the switched mode power supply 2130 . The switch-mode power supply 2130 can be supplied via AC and DC power supplies internal to the switch-mode power supply 2130 (see, for example, FIGS. Figure 24, Figure 27) provides an AC waveform with a DC offset. In an embodiment, the switched mode power supply 2130 may be grounded and coupled in series to a floating DC power supply coupled in series between the switched mode power supply 2130 and the electrostatic chuck 2111.

When the switch mode power supply 2130 includes both AC and DC power supplies, the controller 2132 can control the AC and DC outputs of the switch mode power supply. When the switch mode power supply 2130 is connected in series with the DC power supply, the controller 2132 may only control the AC output of the switch mode power supply 2130 . In an alternative embodiment, controller 2130 may control both the DC power source coupled to switch-mode power supply 2130 and switch-mode power supply 2130 . Those skilled in the art will recognize that while a single controller 2132 is shown, other controllers may also be implemented to control the AC waveform and DC offset provided to the electrostatic chuck 2111.

The electrostatic chuck 2111 may be a dielectric (eg, ceramic) and thus substantially blocks the passage of DC voltages, or it may be a semiconducting material such as doped ceramic. In either case, electrostatic chuck 2111 may have a _second voltage V2 on top surface 2121 of electrostatic chuck 2111, which capacitively couples the voltage to top surface 2118 of substrate 2106 (typically a dielectric) to form first voltage V ₁ .

Plasma 2104 shape and dimensions are not necessarily drawn to scale. For example, the edge of plasma 2104 may be defined by a certain plasma density, in which case plasma 2104 is shown not drawn at any particular plasma density under consideration. Similarly, at least some of the plasma density fills the entire plasma processing chamber 2102 regardless of the plasma 2104 shape as shown. The illustrated shape of plasma 2104 is primarily intended to illustrate sheath 2115 , which has a substantially lower plasma density than plasma 2104 .

Another embodiment of a plasma processing system 2200 is shown in FIG. 22 . In the illustrated embodiment, the switched mode power supply 2230 includes a DC power supply 2234 and an AC power supply 2236 connected in series. The controller 2232 is configured to control the AC waveform with the DC offset output of the switch mode power supply 2230 by controlling both the AC power supply 2236 waveform and the DC power supply 2234 bias or offset. This embodiment also includes an electrostatic chuck 2211 having a grid or mesh electrode 2210 embedded in the chuck 2211. The switched mode power supply 2230 provides both AC and DC bias to the gate electrode 2210 . The DC bias together with the AC component (which is substantially smaller than the DC bias and can therefore be ignored) establishes a third potential V ₄ on the gate electrode 2210 . When the third potential V differs from the potential at the reference layer anywhere within the substrate 2206 ₍ except the bottom surface 2220 of the substrate 2206), the _chuck potential V and the Coulomb chuck force are established, which pull the substrate 2206 Hold to electrostatic chuck 2211. The reference layer is an imaginary plane parallel to the gate electrode 2210 . The AC waveform is capacitively coupled from the gate electrode 2210 through a portion of the electrostatic chuck 2211 and through the substrate 2206 to control a first potential V ₁ on the top surface 2218 of the substrate 2206 . Since the plasma potential _V3 is negligible relative to the plasma _sheath voltage Vsheath, the _first potential V1 and the plasma sheath voltage _{Vsheath are} approximately equal and are considered equal for practical purposes. Therefore, the first potential V ₁ is equal to the potential used to accelerate ions passing through the sheath 2215 .

In an embodiment, the electrostatic chuck 2211 may be doped so as to be sufficiently conductive such that any potential difference across the body of the chuck 2211 is negligible, and thus the grid or mesh electrode 2210 may be substantially in the same position as The same voltage as the _second potential V2.

The gate electrode 2210 may be any conductive planar device embedded in the electrostatic chuck 2211 parallel to the substrate 2206 and configured to be biased by a switch mode power supply 2230 and establish a _chuck potential VCHUCK. Although the gate electrode 2210 is shown embedded in the lower portion of the electrostatic chuck 2211 , the gate electrode 2210 may be positioned closer or further from the substrate 2206 . The gate electrode 2210 also does not have to have a gate pattern. In an embodiment, the gate electrode 2210 may be a solid electrode or a non-solid structure with a non-gate shape (eg, a checkerboard pattern). In an embodiment, the electrostatic chuck 2211 is ceramic or other dielectric, and thus the third potential V ₄ on the gate electrode 2210 is not equal to the first potential V ₁ on the top surface 2221 of the electrostatic chuck 2211 . In another embodiment, the electrostatic chuck 2211 is a slightly conductive doped ceramic, and thus the third potential V _on the gate electrode 2210 may be equal to the _second potential V on the top surface 2221 of the electrostatic chuck 2211 .

Switched mode power supply 2230 produces an AC output that may be a non-sinusoidal output. The switch mode power supply 2230 is capable of operating DC and AC power supplies 2234, 2236 in series because the DC power supply 2234 is AC-conductive and the AC power supply 2236 is DC-conductive. Exemplary AC power supplies that are not DC conducting are certain linear amplifiers that may be damaged when supplied with a DC voltage or current. Using AC conductive and DC conductive power supplies reduces the number of components used in the switch mode power supply 2230 . For example, if the DC power source 2234 is of the AC blocking type, then an AC bypass type or DC blocking type component (eg, a capacitor) may have to be placed in parallel with the DC power source 2234 . If the AC power source 2236 is of the DC blocking type, a DC bypass type or AC blocking type component (eg, an inductor) may have to be placed in parallel with the AC power source 2236 .

In this embodiment, the AC power supply 2238 is generally configured to apply a voltage bias to the electrostatic chuck 2211 in a controllable manner to achieve a desired (or defined) ion energy of the ions bombarding the top surface 2218 of the substrate 2206 distributed. More specifically, AC power supply 2236 is configured to achieve a desired (or defined) ion energy distribution by applying one or more specific waveforms to gate electrode 2210 at specific power levels. And more particularly, AC power source 2236 applies a particular power level to achieve a particular ion energy, and applies the particular power level using one or more voltage waveforms defined by waveform data stored in waveform memory (not shown). Accordingly, one or more specific ion bombardment energies may be selected to perform a controlled etch (or other plasma assisted process) of the substrate 2206 . In one embodiment, the AC power source 2236 may utilize a switch mode configuration (see, eg, FIGS. 25-27 ). The switch mode power supply 2230 (and more specifically the AC power supply 2236 ) can generate AC waveforms as described in various embodiments of the present disclosure.

Those skilled in the art will recognize that the gate electrode 2210 may not be necessary and that other embodiments may be practiced without the gate electrode 2210 . Those skilled in the art will also recognize that gate electrode 2210 is but one example of many devices that may be used to establish the _chuck potential VCHUCK.

Another embodiment of a plasma processing system 2300 is shown in FIG. 23 . The illustrated embodiment includes a switch mode power supply 2330 for providing an AC waveform and DC bias to the electrostatic chuck 2311. Switched mode power supply 2330 includes DC power supply 2334 and AC power supply 2336, both of which may be grounded. The AC power source 2336 generates an AC waveform that is provided to the first grid or mesh electrode 2310 embedded in the electrostatic chuck 2311 via the first conductor 2324 . The AC power source 2336 establishes a potential V ₄ across the first grid or mesh electrode 2310 . A DC power source 2334 generates a DC bias that is provided via the second conductor 2325 to the second grid electrode or mesh electrode 2312 embedded in the electrostatic chuck 2311 . A DC power source 2334 establishes a potential V ₅ across the second grid or mesh electrode 2312 . Potentials _V4 and _V5 are independently controllable via AC and DC power supplies 2336, 2334, respectively. However, the first and second grid or mesh electrodes 2310 , 2312 may also be capacitively coupled and/or there may be a DC coupling between the grid or mesh electrodes 2310 , 2312 via a portion of the electrostatic chuck 2311 . Potentials V ₄ and V ₅ can be coupled if there is AC or DC coupling. Those skilled in the art will recognize that the first and second gate electrodes 2310, 2312 may be disposed in various locations throughout the electrostatic chuck 2311, including disposing the first gate electrode 2310 closer to the second gate electrode 2312. on the substrate 2306.

Another embodiment of a plasma processing system 2400 is shown in FIG. 24 . In this embodiment, switch mode power supply 2430 provides an AC waveform to electrostatic chuck 2411 , wherein the switch mode power supply 2430 output is offset by a DC bias provided by DC power supply 2434 . The AC waveform of the switch mode power supply 2430 has a waveform selected by the controller 2435 to bombard the substrate 2406 with ions from the plasma 2404 having a narrow ion energy distribution. The AC waveform may be a non-sinusoidal waveform (eg, a square wave or pulse) and may be generated via the AC power source 2436 of the switch mode power supply 2430 . The chuck is controlled via a DC offset from a DC power supply 2434 which is controlled by a controller 2433 . DC power supply 2434 may be coupled in series between ground and switched mode power supply 2430 . Switched mode power supply 2430 is floating so that its DC bias can be set by DC power supply 2434 .

Those skilled in the art will appreciate that while the illustrated embodiment shows two separate controllers 2433, 2435, these controllers may be combined into a single functional unit, device or system (such as optional controller 2432) middle. Additionally, controllers 2433 and 2435 may be coupled so as to communicate with each other and share processing resources.

A further embodiment of a plasma processing system 2500 is shown in FIG. 25 . The illustrated embodiment includes a switched mode power supply 2530 that generates an AC waveform that may have a DC offset provided by a DC power supply (not shown). The switch mode power supply can be controlled via an optional controller 2535 comprising voltage and current controllers 2537,2539. Switched mode power supply 2530 may include a controllable voltage source 2538 having a voltage output controlled by a voltage controller 2537 and a controllable current source 2540 having a current output controlled by a current controller 2539 . Controllable voltage and current sources 2538, 2540 may be arranged in parallel. Controllable current source 2540 is configured to compensate for ion current between plasma 2504 and substrate 2506 .

Voltage and current controllers 2537, 2539 may be coupled and in communication with each other. Voltage controller 2537 may also control switch output 2539 of controllable voltage source 2538 . Switch output 2539 may include two switches connected in parallel as shown, or may include any circuitry that converts the output of controllable voltage source 2538 into a desired AC waveform (eg, a non-sinusoidal waveform). Via the two switches, the controlled voltage or AC waveform from the controllable voltage source 2538 can be combined with the controlled current output of the controllable current source 2540 to produce the AC waveform output of the switch mode power supply 2530 .

The controllable voltage source 2538 is shown with a given polarity, but those skilled in the art will recognize that the opposite polarity is equivalent to that shown. Optionally, the controllable voltage and current sources 2538, 2540 along with the switch output 2539 may be part of the AC power supply 2536, and the AC power supply 2536 may be placed in series with a DC power supply (not shown) internal or external to the switch mode power supply 2530 .

FIG. 26 illustrates yet another embodiment of a plasma processing system 2600 . In the illustrated embodiment, switch mode power supply 2630 provides an AC waveform with a DC offset to electrostatic chuck 2611 . The AC component of the waveform is produced via a parallel combination of a controllable voltage source 2638 and a controllable current source 2640 connected to each other by a switch output 2639 . The DC offset is generated by a DC power supply 2634 coupled in series between ground and a controllable voltage source 2638 . In an embodiment, the DC power supply 2634 may be floating rather than grounded. Similarly, switch mode power supply 2630 may be floating or grounded.

System 2600 may include one or more controllers for controlling the output of switch mode power supply 2630 . The first controller 2632 may control the output of the switch mode power supply 2630 via the second controller 2633 and the third controller 2635 , for example. The second controller 2633 can control the DC offset of the switched mode power supply 2630 as generated by the DC power supply 2634 . The third controller 2635 can control the AC waveform of the switch mode power supply 2630 by controlling the controllable voltage source 2638 and the controllable current source 2640 . In an embodiment, the voltage controller 2637 controls the voltage output of the controllable voltage source 2638 and the current controller 2639 controls the current of the controllable current source 2640 . The voltage and current controllers 2637 , 2639 may be in communication with each other and may be part of the third controller 2635 .

Those skilled in the art will appreciate that the above embodiments describing various configurations of the controller relative to the power sources 2634, 2638, 2640 are not limiting and that various other configurations can also be implemented without departing from the present disclosure. For example, the third controller 2635 or the voltage controller 2637 may control the switch output 2639 between the controllable voltage source 2638 and the controllable current source 2640 . As another example, the second and third controllers 2633, 2635 may be in communication with each other (although not shown as such). It should also be understood that the polarity of the controllable voltage and current sources 2638, 2640 is exemplary only and not intended to be limiting.

The switch output 2639 can be operated by alternately switching two parallel switches to shape the AC waveform. Switch output 2639 may comprise any kind of switch including, but not limited to, MOSFETs and BJTs. In one variation, DC power supply 2634 may be disposed between controllable current source 2640 and electrostatic chuck 2611 (in other words, DC power supply 2634 may be floating), and switched mode power supply 2630 may be grounded.

Another embodiment of a plasma processing system 2700 is shown in FIG. 27 . In this variation, the switch mode power supply 2734 is again grounded, rather than being incorporated into the switch mode power supply 2730, where the DC power supply 2734 is a separate component and contributes to the entire switch mode power supply 2730 (rather than just the components within the switch mode power supply 2730). ) to provide a DC offset.

FIG. 28 illustrates a method 2800 according to an embodiment of the disclosure. Method 2800 includes an operation 2802 of placing a substrate in a plasma chamber. Method 2800 also includes an operation 2804 of forming a plasma in the plasma chamber. This plasma can be formed in situ or via a remotely projected source. Method 2800 also includes switching power supply operation 2806 . Switching power operation 2806 involves controllably switching power to the substrate, thereby applying a periodic voltage function to the substrate. The periodic voltage function can be viewed as a pulsed waveform (eg, a square wave) or an AC waveform, and includes the DC offset produced by the DC power supply in series with the switched mode power supply. In an embodiment, a DC power supply may be incorporated into the switched mode power supply and thus in series with the AC power supply of the switched mode power supply. The DC offset creates a potential difference between the top surface of the electrostatic chuck and a reference layer within the substrate, and this potential difference is called the chuck potential. The chuck potential between the electrostatic chuck and the substrate holds the substrate to the electrostatic chuck, thus preventing the substrate from moving during processing. Method 2800 also includes a modulating operation 2808, wherein the periodic voltage function is modulated during the plurality of cycles. The modulation is responsive to a desired (or defined) ion energy distribution at the surface of the substrate such that the desired (or defined) ion energy distribution is achieved on a time averaged basis.

FIG. 29 illustrates another method 2900 according to an embodiment of the disclosure. Method 2900 includes an operation 2902 of placing a substrate in a plasma chamber. Method 2900 also includes an operation 2904 of forming a plasma in the plasma chamber. The plasma can be formed in situ or via a remotely projected source. Method 2900 also includes an operation 2906 of receiving at least one ion energy distribution setting. The settings received in receive operation 2906 may be indicative of one or more ion energies at the surface of the substrate. Method 2900 also includes switching power operation 2908, wherein power to the substrate is controllably switched to achieve: (1) a desired (or defined) distribution of ion energies on a time-averaged basis; and ( 2) Expected chuck potential on a time-averaged basis. A power supply can have an AC waveform and a DC offset.

In summary, in other aspects, the present invention provides a method and apparatus for selectively generating a desired (or defined) ion energy using a switched mode power supply. Those skilled in the art will readily recognize that many variations and substitutions may be made in the present invention, its use and its configuration to achieve substantially the same results as achieved by the embodiments described herein. Therefore, there is no intention to limit the invention to the disclosed exemplary forms. Numerous variations, modifications and alternative constructions fall within the scope and spirit of the disclosed invention.

Claims (36)

1. A method for establishing one or more plasma sheath voltages comprising: providing a modified periodic voltage function to a substrate support of a plasma chamber, wherein the substrate support is coupled to a substrate configured for processing in the plasma, and wherein the The modified periodic voltage function includes the periodic voltage function modified by ion current compensation Ic, wherein said modified periodic voltage function includes pulses and portions between said pulses, wherein said pulse is a function of said periodic voltage function, and wherein the slope of said portion between said pulses is a function of said ion current compensation Ic; accessing an effective capacitance value _C1 representing at least the capacitance of the substrate support; and identifying the value of the ion current compensation Ic that will produce a defined ion energy distribution function for ions reaching the surface _of the substrate, wherein the identification is the effective capacitance C and the part of the slope dV ₀ /dt function, Wherein, the value of the ion current compensation Ic satisfies the following function f: <mrow><mi>f</mi><mrow><mo>(</mo><msub><mi>I</mi><mi>C</mi></msub><mo>)</mo></mrow><mo>=</mo><mfrac><mrow><msub><mi>dV</mi><mn>0</mn></msub></mrow><mrow><mi>d</mi><mi>t</mi></mrow></mfrac><mo>-</mo><mfrac><msub><mi>I</mi><mi>C</mi></msub><msub><mi>C</mi><mn>1</mn></msub></mfrac><mo>=</mo><mn>0.</mn></mrow> 2. The method of claim 1, wherein the defined ion energy distribution is a narrow ion energy distribution. 3. The method of claim 2, wherein the defined ion energy distribution corresponds to a constant voltage at the substrate surface during the portion between the pulses. 4. The method of claim 3, further comprising: Setting the ion current compensation Ic to a first value; determining the sign of said function f; and If the sign of the function f is positive, the ion current compensation Ic is increased, and if the sign of the function f is negative, the ion current compensation Ic is decreased. 5. The method of claim 1, wherein the identifying includes sampling the voltage of the portion between the pulses at two or more time instants. 6. The method of claim 5, wherein the identifying includes calculating the slope dV ₀ /dt from voltages sampled at the two or more time instants. 7. The method of claim 6, wherein said identifying comprises calculating said slope dV ₀ /dt for two or more cycles of said modified periodic voltage function, wherein said two or Each of the plurality of cycles is associated with a different value of the ion current compensation Ic. 8. The method of claim 5, wherein said identifying comprises sampling the voltage of said portion between said pulses during a first period and during a second period, and based at least on these sampled voltage to calculate the slope dV ₀ /dt. 9. The method of claim 1, wherein the ion current compensation _Ic is linearly related to the ion current II through the plasma sheath of the plasma. 10. The method of claim 9, wherein the ionic current compensation _Ic is linearly related to the ionic current Il according to the following equation: where _C1 is the effective capacitance of the plasma chamber as seen by the bias power supply, and Cstray is the accumulated _stray capacitance of the plasma chamber as seen by the bias power supply. 11. The method of claim 10, wherein the effective capacitance _C1 varies with time. 12. The method of claim 10, wherein the ionic current compensation Ic varies with time. 13. The method of claim 1, further comprising providing the modified periodic voltage function to the substrate support such that ions reach the surface of the substrate with a first ion energy. 14. The method of claim 13, wherein the modified periodic voltage function has a first voltage step corresponding to the first ion energy. 15. The method of claim 14 , further comprising providing the modified periodic voltage function to the substrate support by means of the second value of the ion current compensation Ic, thereby broadening the ion energy distribution function . 16. The method of claim 14, wherein the first and second voltage steps are provided in adjacent periods of the modified periodic voltage function. 17. The method of claim 13, wherein the providing has a negligible effect on the density of the plasma. 18. A method for biasing a plasma to achieve a defined ion energy at a surface of a substrate within a plasma processing chamber, the method comprising: applying to the substrate support a modified periodic voltage function comprising a periodic voltage function modified by ion current compensation Ic, said modified periodic voltage function comprising pulses and portions between said pulses; sampling at least one cycle of the modified periodic voltage function to generate voltage data points; estimating a value of a first ion energy at the substrate surface from the voltage data points; and adjusting said modified periodic voltage function until said first ion energy equals said defined ion energy, Wherein, the value of the ion current compensation Ic satisfies the following function f: <mrow><mi>f</mi><mrow><mo>(</mo><msub><mi>I</mi><mi>C</mi></msub><mo>)</mo></mrow><mo>=</mo><mfrac><mrow><msub><mi>dV</mi><mn>0</mn></msub></mrow><mrow><mi>d</mi><mi>t</mi></mrow></mfrac><mo>-</mo><mfrac><msub><mi>I</mi><mi>C</mi></msub><msub><mi>C</mi><mn>1</mn></msub></mfrac><mo>=</mo><mn>0</mn><mo>,</mo></mrow> where C ₁ is an effective capacitance representing at least the capacitance of the substrate support and dV ₀ /dt is the slope of the portion between the pulses. 19. The method of claim 18 , further comprising sampling at least one cycle of the modified periodic voltage function, and calculating the first ion energy after each voltage increase of the adjustment. value. 20. The method of claim 18, wherein the estimating is a function of ion current as an input. 21. The method of claim 18, wherein the ionic current is a function of the ionic current compensation. 22. The method of claim 21 , wherein the following equation is used in said estimating the value of said first ion energy: where ΔV is the voltage step, C is the effective capacitance _of the chamber as seen by the bias supply, and Csheath is the _sheath capacitance of the plasma sheath, which depends on the ion current . 23. The method of claim 22, wherein said adjusting comprises adjusting said step voltage [Delta]V of said modified periodic voltage function until said first ion energy is equal to said defined ion energy. 24. The method of claim 18, further comprising changing the first value of the ion current compensation to a second value, thereby widening the width of the distribution of ion energies. 25. The method of claim 18, wherein the applying and the adjusting have a negligible effect on the plasma density of the plasma. 26. The method of claim 18, wherein the adjusting comprises adjusting a bias supply voltage until the first ion energy is equal to the defined ion energy. 27. A method for achieving the breadth of an ion energy distribution function, the method comprising: providing to a substrate support of a plasma processing chamber a modified periodic voltage function comprising a periodic voltage function modified by ion current compensation Ic, the modified periodic voltage function comprising pulses and portions between the pulses; sampling at least two voltages from the waveform of the modified periodic voltage function at a first instant and at a second instant; calculating the slope of the at least two voltages as dV/dt; comparing the slope to a known reference slope to correspond to the ion energy distribution function width; and adjusting the modified periodic voltage function so that the slope approaches the reference slope, Wherein, the value of the ion current compensation Ic satisfies the following function f: <mrow><mi>f</mi><mrow><mo>(</mo><msub><mi>I</mi><mi>C</mi></msub><mo>)</mo></mrow><mo>=</mo><mfrac><mrow><msub><mi>dV</mi><mn>0</mn></msub></mrow><mrow><mi>d</mi><mi>t</mi></mrow></mfrac><mo>-</mo><mfrac><msub><mi>I</mi><mi>C</mi></msub><msub><mi>C</mi><mn>1</mn></msub></mfrac><mo>=</mo><mn>0</mn><mo>,</mo></mrow> where C ₁ is an effective capacitance representing at least the capacitance of the substrate support and dV ₀ /dt is the slope of the portion between the pulses. 28. The method of claim 27, wherein the first instant occurs during a first period of the modified periodic voltage function, and the second instant occurs during a period of the modified periodic voltage function during the second cycle of . 29. The method of claim 27, wherein the first instant and the second instant occur during the same period of the modified periodic voltage function. 30. The method of claim 27, wherein the sampling is performed at a sampling rate of at least 400 kHz. 31. A plasma processing system comprising: a plasma processing chamber configured to contain a plasma; a substrate support disposed within the plasma processing chamber and positioned to support a substrate during plasma processing; a power supply that provides a periodic voltage function to the substrate support, the periodic voltage function having pulses and portions between the pulses; an ion current compensation component that modifies the slope dV ₀ /dt of the portion between the pulses to form a periodic voltage function supplied to the substrate support comprising a modification by ion current compensation Ic The modified periodic voltage function of ; and a controller in communication with the power supply and the ion current compensation component, Wherein, the value of the ion current compensation Ic satisfies the following function f: <mrow><mi>f</mi><mrow><mo>(</mo><msub><mi>I</mi><mi>C</mi></msub><mo>)</mo></mrow><mo>=</mo><mfrac><mrow><msub><mi>dV</mi><mn>0</mn></msub></mrow><mrow><mi>d</mi><mi>t</mi></mrow></mfrac><mo>-</mo><mfrac><msub><mi>I</mi><mi>C</mi></msub><msub><mi>C</mi><mn>1</mn></msub></mfrac><mo>=</mo><mn>0</mn><mo>,</mo></mrow> Wherein, C ₁ is an effective capacitance representing at least the capacitance of the substrate support. 32. The system of claim 31, wherein the controller adjusts the magnitude of the ion current compensation until a defined ion energy distribution function of ions reaching the surface of the substrate is achieved. 33. The system of claim 31 , wherein the controller is further configured to identify the magnitude of the pulse of the periodic voltage function if the pulse of the periodic voltage function is provided to the substrate support. The pulse will generate a defined ion energy of the ions reaching the surface of the substrate. 34. The system of claim 33 , wherein the controller adjusts the magnitude of the pulses of the periodic voltage function until the defined ion energy of ions reaching the surface of the substrate is achieved . 35. A method for monitoring an ion current of a plasma configured to process a substrate, the method comprising: taking a first sample of the modified periodic voltage function taking into account ion current compensation having a first value; taking a second sample of said modified periodic voltage function taking into account said ion current compensation having a second value; determining a slope of the modified periodic voltage function as a function of time based on the first sample and the second sample; and A third value for the ion current compensation at which a constant voltage on the substrate will exist for at least one cycle of the modified periodic voltage function is calculated based on the slope. 36. The method of claim 35, further comprising calculating a sheath voltage across a plasma sheath of the plasma.