KR101328800B1 - Characteristic controlling method of pulsed plasma using Multi-frequency RF pulsed power - Google Patents

Abstract

Disclosed is a method of controlling a characteristic of a pulsed plasma using pulse power of multiple frequencies. RF pulse power of multiple frequencies is applied to the source electrode portion and / or the bias electrode portion of the plasma generating device to form a pulsed plasma, and the pulsing state, period, and duty ratio of two or more RF powers are changed. By controlling the period and duty ratio of the pulses it is possible to control the characteristics of the pulsed plasma to suit each process.

Description

Characteristic controlling method of pulsed plasma using Multi-frequency RF pulsed power}

The present invention relates to a method for controlling the characteristics of a pulsed plasma using a multi-frequency RF pulse power, and more particularly, duty ratio according to whether or not pulse power of two or more RF powers applied during pulse plasma formation, and on / off period control. The present invention relates to a method of controlling the characteristics of a pulsed plasma using a multi-frequency RF pulse power for controlling the characteristics of the pulsed plasma used in each process through a change in ratio).

In accordance with the trend of miniaturization and integration of components used in semiconductor devices, recent efforts to increase the size of wafers used as bases in semiconductor manufacturing and to reduce the size of the wafers to increase the cost have been actively made.

Meanwhile, as the degree of integration of semiconductor devices increases, a method of treating a surface of a wafer through plasma is used to form finer patterns.

1 is a cross-sectional view showing a conventional capacitively coupled plasma (CCP) generating device.

Referring to FIG. 1, the capacitively coupled plasma generation device is installed in a process chamber 10, a source electrode portion 20 provided on an upper portion of the process chamber, and a direction opposite to the source electrode portion 20. 40 is composed of a bias electrode portion 30 to be seated. The bias electrode part 30 serves to suck and compress the wafer 40.

When RF power is applied to the source electrode portion 20 and the bias electrode portion 30 of the capacitively coupled plasma generator, an electric field is induced between the source electrode portion 20 and the bias electrode portion 30. At the same time, when the reaction gas is injected into the process chamber 10 through a gas injection hole (not shown) provided on the top or sidewall of the process chamber 10, the reaction gas is induced by an electric field induced in the process chamber 10. Transform into plasma state. By the generated plasma, a wafer treatment process such as etching or thin film deposition on the wafer 40 is performed.

In this case, a conventional continuous wave (CW) plasma is formed by applying RF power to the plasma generating apparatus for processing a large-diameter wafer, thereby processing a substrate such as etching, deposition, and ashing. In the case of performing the electron temperature, the decomposition of the injected reactive gas due to the high electron temperature is excessive, and the generation of charge is excessively active, resulting in a high incidence of physical and electrical damage.

Meanwhile, Korean Patent No. 10-0416715 discloses an ion implantation method using pulsed plasma and a technology thereof. This method includes placing a sample on a sample stage in a vacuum chamber, supplying a gas to be plasmaded in the vacuum chamber, radiating an RF pulse to the gas, and applying a negative DC high voltage to the sample to change the sample into a plasma state. Injecting to the surface of the. In this case, however, the RF pulse power of a single frequency is applied, and it is difficult to control the characteristics of the plasma such as the control of electron energy distribution and the uniformity of plasma by simply applying the RF pulse power having a single frequency as described above. There was this.

Accordingly, an object of the present invention is to apply a multi-frequency RF pulse power to the source electrode portion and / or the bias electrode portion constituting the plasma generating device, and to adjust the density or electron temperature of the plasma through a mixture of the applied multi-frequency RF pulse power It is to provide a method of controlling the characteristics of the pulsed plasma used in the wafer processing process by changing to suit each process.

According to an aspect of the present invention, there is provided a plasma generating apparatus including a gas injection hole, a source electrode part, and a bias electrode part, applying at least two RF powers at least one of which is pulsed to the source electrode part; Applying at least one RF power that is not pulsed to the bias electrode part and injecting a reaction gas into the gas inlet to form a pulsed plasma, the frequency of two or more RF powers applied to the source electrode part; Is selected to have different values.

In addition, providing a plasma generating apparatus comprising a gas injection port, a source electrode portion and a bias electrode portion, applying a single RF pulse power to the source electrode portion, applying a single RF pulse power to the bias electrode portion And forming a pulse plasma by injecting a reaction gas into the gas inlet, wherein the frequencies of the RF pulse powers of the source electrode and the bias electrode are selected to have different values, and are coupled to each other. It is characterized by the configuration.

According to an embodiment of the present invention, a method of controlling a characteristic of a pulsed plasma using a multi-frequency RF pulse power may be performed by applying a multi-frequency RF pulse power to a source electrode part and / or a bias electrode part constituting a plasma generating device. Accordingly, the duty ratio can be changed by adjusting the on / off period, thereby controlling the characteristics of the plasma to be suitable for each process by controlling the degree of charge cancellation and the reactivity.

1 is a cross-sectional view showing a conventional capacitively coupled plasma (CCP) generating device.
FIG. 2 is a diagram showing an electron density change of a pulse plasma formed by applying RF pulse power.
FIG. 3 is a diagram showing an electron temperature change of a pulse plasma formed by applying RF pulse power.
4 is a diagram illustrating a multi-frequency RF pulse power structure applied to a source electrode unit.
5 is a diagram illustrating a multi-frequency RF pulse power structure applied to a bias electrode unit.
6A and 6B illustrate a multi-frequency RF pulse power structure applied to a source electrode part and a bias electrode part.
7A to 7C are diagrams illustrating embodiments of various modes of applying time-modulated time (RF) pulse power of multiple frequencies to a source electrode unit.
FIG. 8 is a diagram illustrating a method of applying and coupling RF pulse power of high frequency wave (HF) to the source electrode portion and RF pulse power of low frequency wave (LF) to the bias electrode portion.
9A to 9C illustrate a case where the RF pulse power of the high frequency wave (HF) is applied alone, the case of applying the RF pulse power of the low frequency wave (LF) alone and the case of applying the RF pulse power mixed with the high frequency and the low frequency plasma. It is a figure which shows an electron energy distribution function (EEDF).
10A to 10D are SEM images illustrating a shape in which a silicon oxide film is etched using a pulsed plasma according to an embodiment of the present invention.

The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The plasma generating apparatus that can be used to perform the present invention may be a capacitively coupled plasma (CCP) generating apparatus, but the present invention is not limited thereto, and any plasma generating apparatus capable of applying RF power in a pulse form may be used. Can be. Hereinafter, a capacitively coupled plasma (CCP) generating device including a source electrode part and a bias electrode part will be described as an example.

RF power is applied to at least one of the source electrode portion and the bias electrode portion in a pulse form. The RF pulse power may be applied by pulsing by connecting a separate device to existing RF power, or by applying RF pulse power. Pulsed wave plasma may be formed by applying RF pulse power in one of the above methods.

At this time, the plasma is generated at the on time of the pulse, and the plasma is extinguished at the off time. The duty ratio (DR) is changed according to the period of the pulse power applied as described above, affecting the characteristics of the generated pulsed plasma. The duty ratio means a ratio of the on period and the off period of the plasma. For example, in the case of DR 60%, the duty ratio means 60% of the pulse plasma and 40% of the off period. This means that the on and off cycles are the same.

FIG. 2 is a diagram showing an electron density change of a pulse plasma formed by applying RF pulse power.

FIG. 3 is a diagram showing an electron temperature change of a pulse plasma formed by applying RF pulse power.

Referring to FIGS. 2 and 3, the characteristics of the pulsed plasma may be controlled by changing the duty ratio by pulsing the RF power or adjusting the on / off period of the pulse when applying the RF pulse power. Representative of these is the control of the electron density and electron temperature of the plasma. When the RF power is applied without pulsing, the electron density and the electron temperature are continuously high. Accordingly, decomposition of the injected reactive gas becomes active, the potential of the plasma increases, and the generation of charge becomes excessively active, thereby increasing the physical and electrical damage incidence of the wafer. On the other hand, when pulsing RF power or applying RF pulse power, the on / off period of the plasma can be changed to control the increase and decrease of the electron density and electron temperature. And the like can have an excellent effect on the performance of the process.

4 is a diagram illustrating a multi-frequency RF pulse power structure applied to a source electrode unit.

Referring to FIG. 4, it is possible to change the density and reactive species (reactive radicals, ions, and electrons) of the pulsed plasma formed by mixing and applying the multi-frequency RF pulse power at the source electrode part. At this time, the multi-frequency configuration of the RF pulse power applied to the bias electrode part is very high frequency (VHF) in the range of 60 MHz to less than several hundred MHz and high frequency in the range of 13.56 MHz to less than 60 MHz. , HF) or a mixture of very high frequency (VHF) ranging from 60 MHz to less than several hundred MHz and low frequency (LF) ranging from 0.1 MHz to less than 13.56 MHz. In addition, it is possible to prevent the effect of excessive concentration of energy to the lower by applying a lower frequency RF power than the ground (ground) or the source electrode portion to the bias electrode portion.

5 is a diagram illustrating a multi-frequency RF pulse power structure applied to a bias electrode unit.

Referring to FIG. 5, RF pulse power of multiple frequencies may be mixed and applied to the bias electrode part to change the density and reactive species (reactive radicals, ions, and electrons) of the pulsed plasma. At this time, the multi-frequency configuration of the RF pulse power applied to the bias electrode part is very high frequency (VHF) in the range of 60 MHz to less than several hundred MHz and high frequency in the range of 13.56 MHz to less than 60 MHz. , HF) or a mixture of very high frequency (VHF) ranging from 60 MHz to less than several hundred MHz and low frequency (LF) ranging from 0.1 MHz to less than 13.56 MHz. In addition, by applying RF power of a lower frequency than the ground or bias electrode portion to the source electrode portion, it is possible to prevent the effect of excessive concentration of energy to the top.

6A and 6B illustrate a multi-frequency RF pulse power structure applied to a source electrode part and a bias electrode part.

6A and 6B, the multi-frequency application is not limited to either the source electrode portion or the bias electrode portion, and the multi-frequency is applied by applying an RF pulse power having one or two frequencies to the source electrode portion and the bias electrode portion. Can be configured.

For example, as shown in FIG. 6A, one RF pulse power may be applied to each of the source electrode part and the bias electrode part so that they are coupled to form multiple frequencies, and the multiple frequencies are source electrode parts / biased. The electrode unit may be applied in a configuration of ultra high frequency (VHF) / low frequency (LF) or high frequency (HF) / low frequency (LF). That is, when applying the RF pulse power of the ultra-high frequency (VHF) or the high frequency (HF) to the source electrode portion, the RF pulse power of the low frequency (LF) may be applied to the bias electrode portion.

In addition, it is also possible to apply and couple two multi-frequency RF pulse powers to the source electrode portion and also apply the two multi-frequency RF pulse powers to the bias electrode portion. The configuration of the multi-frequency applied to the source electrode portion may be a configuration of ultra-high frequency (VHF) / low frequency (LF) or high frequency (HF) / low frequency (LF) as described above, the corresponding bias electrode portion in the source It is preferable to apply a frequency having a value smaller than the frequency applied to the electrode portion.

At this time, the frequency range of the ultra-high frequency, high frequency and low frequency applied in each of the above cases is as described above. Ultra high frequency (VHF) or high frequency (HF) applied to the source electrode portion adjusts the density of the plasma, and low frequency (LF) applied to the bias electrode portion can control the plasma characteristics independently by controlling the energy of the ions. There is an advantage.

7A to 7C are diagrams illustrating embodiments of various modes of applying time-modulated time (RF) pulse power of multiple frequencies to a source electrode unit.

Referring to FIGS. 7A to 7C, for example, an RF pulse power of 100 MHz may be applied as an ultra high frequency and an RF pulse power of 60 MHz may be applied as a high frequency. In this case, various methods may be used to apply the multiple frequencies to the source electrode unit. As shown in FIG. 7A, the multiple frequencies may be divided and applied to the pulse on period of the source electrode unit before and after time. That is, RF pulse power of 100 MHz may be applied as a very high frequency for a predetermined time of a pulse on period, and RF pulse power of 60 MHz may be applied as a high frequency for the remaining time.

In addition, as shown in FIG. 7B, the multiple frequencies may be applied to the pulse on period of the source electrode part at the same time and the simultaneous removal to the pulse off period of the source electrode part. Therefore, in this case, since the ultra-high frequency RF pulse power of 100 MHz and the high frequency RF pulse power of 60 MHz are simultaneously applied in the on-cycle, multiple frequencies are merged.

As shown in FIG. 7C, the high frequency RF pulse power of 60 MHz is applied to the pulse on period 1 of the source electrode part, and the continuous wave is continuously applied to the ultra high frequency RF pulse power of 100 MHz to the pulse on period 2 of the source electrode part. It can be operated like a plasma.

FIG. 8 is a diagram illustrating a method of applying and coupling RF pulse power of high frequency wave (HF) to the source electrode portion and RF pulse power of low frequency wave (LF) to the bias electrode portion.

Referring to FIG. 8, RF frequencies of ultra high frequency (VHF) or high frequency (HF) are applied to the source electrode portion, and RF frequencies of low frequency (LF) are applied to the bias electrode portion to couple the multiple frequencies. Can be configured.

9A to 9C illustrate a case where the RF pulse power of the high frequency wave (HF) is applied alone, the case of applying the RF pulse power of the low frequency wave (LF) alone and the case of applying the RF pulse power mixed with the high frequency and the low frequency plasma. It is a figure which shows an electron energy distribution function (EEDF).

9A to 9C, it can be seen that when the high frequency HF and the low frequency LF are mixed and applied, different electron energy distributions are formed than when the high frequency HF and the low frequency LF are applied alone. . Therefore, when two or more of the multiple frequencies are mixed, the degree of dissociation of the reactive gas injected by the mixing of the electron energy distribution may be changed, and thus the characteristics of the plasma may be changed.

As described above, in the embodiments of FIGS. 4 to 9D, when multiple frequencies are applied to the source electrode part and / or the bias electrode part, a method of pulsing RF power or applying RF pulse power to all electrode parts is described. The present invention is not limited thereto, and the pulsing may be controlled by pulsing only the RF power of the source electrode part or the bias electrode part or pulsing the source electrode part and the bias electrode part. By varying the pulsing as described above, it is possible to change the characteristics of the plasma, there is an advantage that can create a plasma effect required for each process.

10A to 10D are SEM images illustrating a shape in which a silicon oxide film is etched using a pulsed plasma according to an embodiment of the present invention.

The process condition is a configuration in which multiple frequencies are applied to the source electrode portion, and the multi-frequency configuration is set to ultra high frequency (VHF) / low frequency (LF). At this time, 60MHz was applied as the ultrahigh frequency (VHF) and 2MHz was applied as the low frequency (LF), and the shape of the silicon oxide film which was etched using pulsed plasma for different times at a depth of about 1 micrometer (m). to be. The sample consists of a mask of an amorphous carbon layer (ACL) and a silicon oxide dielectric layer of several microns, which is subjected to an etching process using CW plasma, and a single pulsing with a period of 5 kHz at a high frequency 60 MHz power. (single pulsing) was used to observe the varying duty ratio.

Referring to FIG. 10A, in the case of CW plasma, it can be seen that distortion of the lower portion of the etched profile has been generated, while RF pulse power of multiple frequencies is applied by pulsing RF power of ultra-high frequency. 10B to 10D in which the duty ratio is changed, the electron temperature decreases and the etching rate decreases as the duty ratio decreases, but the selectivity and shape profile are improved. In addition, it can be seen that the distortion of the lower portion of the etched profile is reduced.

According to the present invention, a method of controlling the characteristics of a pulsed plasma using a multi-frequency RF pulse power can change the characteristics of a plasma to be suitable for each process by applying a multi-frequency RF pulse power to a source electrode part and / or a bias electrode part. Therefore, there is an advantage of significantly reducing plasma damage in a surface treatment process of a substrate such as etching or deposition using plasma.

10: process chamber
20: source electrode portion
30: bias electrode part
40: wafer

Claims (12)

Providing a plasma generating device including a gas injection hole, a source electrode part, and a bias electrode part;
Injecting a reaction gas into the gas inlet;
Forming a pulsed plasma between the source electrode portion and the bias electrode portion, wherein the first RF AC power and the first RF AC power having different frequency values are generated at any one of the source electrode portion and the bias electrode portion during the generation period of the pulse plasma; Applying 2 RF AC power, wherein at least one of the first and second RF AC powers is pulsed; And
And applying a third non-pulsed RF alternating current power to the other one of the source electrode portion and the bias electrode portion. The method of claim 1,
Applying a first RF AC power and a second RF AC power having different frequency values to the source electrode, wherein at least one of the first and second RF AC powers is pulsed,
A method of controlling the characteristics of a pulsed plasma using a multi-frequency RF pulse AC power for applying a third RF AC power that is not pulsed to the bias electrode part. 3. The method of claim 2,
Any one of the frequencies of the first RF AC power and the second RF AC power applied to the source electrode unit is selected from the range of 60MHz or less and less than 100MHz, the other is selected from the range of 13.56MHz or less and less than 60MHz, or 0.1MHz The characteristic control method of the pulsed plasma using the RF pulse AC power of the multi-frequency selected in the range below 13.56MHz. 3. The method of claim 2,
The first RF AC power and the second RF AC power applied to the source electrode portion control method of the pulsed plasma using a multi-frequency RF pulse AC power is applied by modulating the time in the plasma generation cycle. 3. The method of claim 2,
And the first RF AC power and the second RF AC power applied to the source electrode are simultaneously applied during the plasma generation cycle. 3. The method of claim 2,
The first RF AC power and the second RF AC power applied to the source electrode portion control characteristics of the pulsed plasma using a multi-frequency RF pulse AC power is continuously applied without the extinction period of the plasma. 3. The method of claim 2,
And a frequency of the third RF AC power applied to the bias electrode part is lower than that of the ground or the source electrode part. The method of claim 1,
Applying a first RF AC power and a second RF AC power having different frequency values to the bias electrode part, wherein at least one of the first and second RF AC powers is pulsed,
And a pulse plasma characteristic control method using a multi-frequency RF pulse alternating current power to apply a third RF alternating current power not pulsed to the source electrode portion. 9. The method of claim 8,
One of the frequencies of the first RF AC power and the second RF AC power applied to the bias electrode part is selected from a range of 60 MHz or more and less than 100 MHz, and the other is selected from a range of 13.56 MHz or more and less than 60 MHz, or 0.1 MHz. The characteristic control method of the pulsed plasma using the RF pulse AC power of the multi-frequency selected in the range below 13.56MHz. 9. The method of claim 8,
And a frequency of the third RF AC power applied to the source electrode portion is lower than that of the ground or the bias electrode portion. delete delete

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