EP1112587A1

EP1112587A1 - Device and method for etching a substrate by means of an inductively coupled plasma

Info

Publication number: EP1112587A1
Application number: EP00949074A
Authority: EP
Inventors: Volker Becker; Franz Laermer; Andrea Schilp
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1999-07-20
Filing date: 2000-06-06
Publication date: 2001-07-04
Also published as: WO2001006539A1; KR20010075207A; US7811941B1; JP4690618B2; KR100752064B1; DE19933842A1; JP2003505868A

Abstract

The invention relates to a method for etching a substrate (10), especially a silicon body, by means of an inductively coupled plasma (14) and to a device for the implementation of said method. To this end, a high-frequency electromagnetic alternating field is generated with an ICP source (13). Said field produces an inductively coupled plasma (14) consisting of reactive particles in a reactor (15). The inductively coupled plasma (14) is produced by the effect of the high-frequency electromagnetic alternating field on a reactive gas. A device is also provided by means of which the plasma power coupled with the ICP source (13) into the inductively coupled plasma (14) by means of the high-frequency electromagnetic alternating field can be pulsed in such a way that a pulsed high-frequency power can be coupled at least temporarily as plasma power into the inductively coupled plasma. The pulsed plasma power can also be combined or correlated with a pulsed magnetic field and/or a pulsed substrate electrode power.

Description

Device and method for etching a substrate by means of an inductively coupled plasma

The invention relates to a device and a method which can be carried out therewith for etching a substrate, in particular a silicon body, by means of an inductively coupled plasma according to the category of the independent claims.

State of the art

In order to implement an anisotropic high-rate etching process, for example for silicon, using an inductive plasma source, it is necessary in processes such as are known, for example, from DE 42 41 045 C2, to carry out an efficient sidewall passivation in the shortest possible time using so-called passivation steps and also to achieve the highest possible To achieve concentration of silicon-etching fluorine radicals during so-called etching steps. In order to increase the etching rate, it makes sense to work with the highest possible high-frequency powers on the inductive plasma source and thereby as high as possible

To couple plasma power into the generated inductively coupled plasma. However, there are limits to the plasma services that can be coupled in, which result on the one hand from the load-bearing capacity of the electrical components of the plasma source, and on the other hand are also of a technical nature. Thus high high-frequency powers of the inductive plasma source, ie high plasma powers to be coupled in, intensify harmful electrical interventions from the source area into the generated inductively coupled plasma, which deteriorate the etching results on the substrate wafer.

In addition, in the case of etching processes according to the type of DE 42 41 045 C2, stability problems occur in the plasma coupling in the switching phases between etching and passivation steps with very high plasma outputs. This is due to the fact that power reflections and voltage spikes that occur during the switchover phases have a destructive effect on the electrical circuit of the plasma source (coil, connected capacities, generator output stage, etc.) at high powers to be coupled in in the kWatt range.

For this purpose, the application DE 199 00 179 already describes an inductive plasma source which has been further developed compared to DE 42 41 045 C2 and which is suitable for particularly high plasma powers by means of a loss-free symmetrical high-frequency supply of the coil of the inductive plasma source, and which generates an inductive plasma which is particularly useful is poor in interference. But also for this type of source there is a practicable power limit of about 3 k att to 5 k att, above which the required high-frequency components become extremely expensive or problems regarding the plasma stability become excessive.

From the application DE 199 198 32 it is also already known that the inductively coupled plasma with a high-frequency electromagnetic alternating field coupled plasma power adiabatically to vary between individual process steps, in particular alternating etching and passivation steps.

Such an adiabatic power transition, i.e. A gradual start-up or reduction of the coupled plasma power, with simultaneous continuous adaptation of the impedance of the ICP source to the respective plasma impedance dependent on the coupled plasma power by means of an automatic matching network or an impedance transformer (“matchbox”) makes it possible to explain the problems relating to power reflection and voltage increase when switching on and off plasma powers in the range from 1 kWatt to 5 kWatt. However, a typical duration of the switch-on processes is in the range from 0.1 sec to 2 sec. Faster power changes are not possible with this approach.

Advantages of the invention

The device according to the invention and the method carried out therewith has the advantage over the prior art that it is a variably adjustable, pulsed

High-frequency power is generated, which can be coupled as plasma power into the inductively coupled plasma, the pulsing of the plasma power taking place very quickly, for example within microseconds, and at the same time being associated with power changes of several thousand watts.

The pulsation of the plasma power continues with a significant improvement in the economy of the ICP source connected and opens the possibility to reduce the mean plasma power without reducing the etching rate or to increase the etching rate with unchanged mean plasma power. Furthermore, pulsing the plasma power can effectively reduce electrical interference effects from the source area of the ICP source.

Advantageous developments of the invention result from the measures mentioned in the subclaims.

It is particularly advantageous if the plasma plasma system according to the invention is provided with a balanced, symmetrically constructed and symmetrically powered configuration of the ICP source. In this way, the homogeneity of the etching rates over the surface of the substrate is significantly improved and the electrical coupling of high plasma powers into the generated plasma is considerably simplified.

It is also advantageous if an additional, constant or time-varying longitudinal magnetic field is generated in the interior of the reactor, which leads the generated, inductively coupled plasma from the plasma source in the manner of a magnetic bottle to the substrate to be etched.

This magnetic field, the direction of which is at least approximately or predominantly parallel to the direction defined by the connecting line between the substrate and the inductively coupled plasma, significantly improves the use of the coupled high-frequency power to generate the desired plasma species (electrons, ions, free radicals), ie the efficiency of the plasma generation , Therefore, at same plasma power, significantly higher etching rates are possible.

A particularly good guidance of the generated plasma through the magnetic field and a particularly low penetration of the generated magnetic field onto the substrate itself to be etched further advantageously results if an aperture is also provided, which is arranged concentrically to the inner wall of the reactor, preferably about 5 cm is arranged above the substrate arranged on a substrate electrode. This aperture leads to an improved uniformity of the etching over the substrate surface and at the same time avoids in the case of a time-varying magnetic field high induced voltages in the substrate to be etched, which may damage electronic components there.

It is also very advantageous if components are integrated in the ICP coil generator which are used for impedance matching as a function of the ones to be coupled in

Plasma power can vary the frequency of the generated alternating electromagnetic field, since it enables a particularly fast switchover between plasma power pulses and pulse pauses.

This frequency variation advantageously prevents high reflected powers occurring back into the ICP coil generator when the plasma power is pulsed, in particular in times of a rapidly changing coupled plasma power, ie in the case of pulse-to-pause transitions. Another major advantage of an impedance matching that is as good as possible at all times via a variable frequency of the high-frequency power of the ICP coil generator is that this frequency change is very great can be carried out quickly since it is only limited by the control speed of an electronic circuit which carries out the frequency variation. Response times or very rapid changes in the output power of the ICP coil generator in the microsecond range are thus possible in a stable manner, which makes it possible to work with plasma power pulses during the etching and / or passivation steps, the duration of which is in the microsecond range.

Since very rapid impedance changes in the plasma occur during pulsed operation of the ICP source, it is impossible according to the prior art for single pulse powers in the kWatt range, in particular in the range above 3 kWatt, to have high reflected power when switching the on and off coupled

Avoid high-frequency power pulses or at least render them harmless. In contrast, the device according to the invention also ensures the impedance matching of inductively coupled plasma or ICP source and ICP coil generator at all times in this case.

Pulsed operation of the ICP source has the essential advantage over continuous operation that during the high-frequency power pulses or

Plasma power pulses achieve a much higher plasma density than with continuous operation. This is due to the fact that the generation of an inductive plasma is a highly non-linear process, so that the average plasma density in this pulsed operating mode is higher than with an average plasma power corresponding to the time average. Therefore, based on the time average, more reactive species and ions are effectively obtained in pulse mode than in continuous wave mode. This is especially true when so-called "giant pulses" are used, ie relatively short and extremely powerful high-frequency power pulses of, for example, 20 kWatt peak power, as is now possible with the device according to the invention, the mean plasma power then being, for example, only 500 watts.

In this case, inevitable heat losses in the ICP coil generator and other system components of the plasma treatment system are advantageously correlated with the relatively low time average of the plasma power, while desired plasma effects, in particular the achievable etching rates, advantageously correlate with the peak powers that occur. As a result, the efficiency of generating reactive species and ions is significantly improved.

Another advantage of pulsed operation of the ICP source is that, in the pauses between the high-frequency power pulses, disruptive electrical charges can be discharged on the substrate to be etched, and thus the overall profile control during etching is improved.

Finally, it is very advantageous if the pulsing of the generated magnetic field is temporally correlated or synchronized with the pulsing of the injected plasma power and / or the pulsing of the high-frequency power injected into the substrate via the substrate voltage generator. The temporal synchronization of the pulsation of the magnetic field and the coupled plasma power results in a significant reduction in the ohms occurring in the magnetic field coil, see heat losses, which alleviates problems of cooling and temperature control of the magnetic field coil. If, for example, the injected plasma power is operated with a pulse-to-pause ratio of 1:20, the current through the magnetic field coil can also be pulsed, for example with a pulse-to-pause ratio of 1:18, which advantageously means that the required Heat dissipation from the magnetic field coil reduced to 1/18 of the original value. At the same time, the consumption of electrical energy drops accordingly.

drawings

Exemplary embodiments of the invention are explained in more detail with reference to the drawings and the description below. FIG. 1 shows a schematic plasma setting system, FIG. 2 shows an electronic one

Feedback circuit with connected ICP source, Figure 3 shows an example of a filter characteristic, Figure 4 shows an example of a time synchronization of high-frequency plasma power pulses coupled into the plasma with magnetic field pulses, Figure 5 shows one in the

6, an equivalent circuit diagram for the generation of the substrate electrode voltage and FIG. 7, the change in the substrate electrode voltage during a high-frequency power pulse as a function of the number of oscillation periods.

embodiments

A first exemplary embodiment of the invention is explained in more detail with reference to FIG. 1. For this purpose, a plasma set 5 initially has a reactor 15, in the upper region of which in an inductively coupled plasma 14 is generated in a manner known per se via an ICP source 13 (“Inductively Coupled Plasma”). Furthermore, there is a gas supply 19 for supplying a reactive gas such as SF ₆ , C1F ₃ , 0 ₂ , CF ₈ , C ₃ F ₆ , SiF ₄ or NF ₃ , a gas discharge 20 for the removal of

Reaction products, a substrate 10, for example a silicon body or silicon wafer to be structured with the etching method according to the invention, a substrate electrode 11 in contact with the substrate 10, a substrate voltage generator 12 and a first impedance transformer 16. The substrate voltage generator 12 couples a high-frequency alternating voltage or high-frequency power into the substrate electrode 11 and above that into the substrate 10, which accelerates the inductively coupled

Plasma 14 generated ions on the substrate 10 causes. The high-frequency power or alternating voltage coupled into the substrate electrode 11 is typically between 3 watts and 50 watts or 5 volts and 100 volts in continuous wave mode or in pulsed mode in the time average over the pulse sequence.

Furthermore, an ICP coil generator 17 is provided, which is connected to a second impedance transformer 18 and above that to the ICP source 13. Thus, the ICP source 13 generates a high-frequency alternating electromagnetic field and above it in the reactor 15 an inductively coupled plasma 14 composed of reactive particles and electrically charged particles (ions), which are created by the action of the high-frequency alternating electromagnetic field on the reactive gas. For this purpose, the ICP source 13 has a coil with at least one turn. The second impedance transformer 18 is preferably designed in the manner proposed in the application DE 199 00 179.0, so that a balanced, symmetrical configuration and supply of the ICP source 13 via the ICP coil generator 17 is provided. This ensures in particular that the high-frequency AC voltages applied to the two ends of the coil of the ICP source 13 are at least almost in phase opposition to one another. Furthermore, the center tap 26 of the coil of the ICP source 13, as indicated in FIG. 2, is preferably grounded.

The plasma etching system 5 also carries out, for example, the anisotropic high rate etching process known from DE 42 41 045 C2 for silicon with alternating etching and passivation steps. With regard to further details, known per se to the person skilled in the art, of the plasma deposition system 5, which is known from the prior art as far as described so far, and of the etching process carried out therewith, in particular with regard to the reactive gases, the process pressures and the substrate electrode voltages in the respective etching steps or passivation steps therefore, reference is made to DE 42 41 045 C2.

The plasma set 5 according to the invention is also suitable for process control as described in the application DE 199 27 806.7.

In particular, when the substrate 10 is etched, the passivation steps in the reactor 15 are passivated with a process pressure of 5 μbar to 20 μbar and with an average plasma power of 300 to 1000 watts coupled into the plasma 14 via the ICP source 13. C ₄ F ₈ or C ₃ F ₆ , for example, is suitable as the passivating gas. A process pressure of 30 μbar to is then during the subsequent etching steps 50 μbar and a high mean plasma power of 1000 to 5000 watts. SF ₆ or C1F ₃ , for example, is suitable as the reactive gas. In the context of the invention, mean plasma power is always understood to mean a coupled-in plasma power averaged over a large number of plasma power pulses.

Furthermore, in the plasma system 5 between the inductively coupled plasma 14 and the ICP source 13, i.e. the actual plasma excitation zone, and the substrate 10, a so-called “spacer” is placed as a spacer 22 made of a non-ferromagnetic material such as aluminum. This spacer 22 is inserted concentrically into the wall of the reactor 15 as a spacer ring and thus forms the reactor wall in some areas a typical height of approx. 5 cm to 30 cm with a typical diameter of the reactor 15 of 30 cm to 100 cm.

In a preferred embodiment of the exemplary embodiment, the spacer 22 is further surrounded by a magnetic field coil 21, which has, for example, 100 to 1000 turns and is wound from a copper wire that is sufficiently thick for the amperage to be used. In addition, copper pipes can be included in the magnetic field coil 21 through which cooling water flows in order to dissipate heat losses from the magnetic field coil 21.

Alternatively, it is also possible to wind the magnetic field coil 21 itself out of a thin copper tube which is coated with an electrically insulating material and through which cooling water flows directly. An electric current of, for example, 10 to 100 amperes is passed through the magnetic field coil 21 via a power supply unit 23.

In the first exemplary embodiment explained, this is, for example, a direct current which generates a static magnetic field inside the reactor 15, which in the case of a magnetic field coil 21 with 100 turns and a length of 10 cm and a diameter of 40 cm, for example, a magnetic field strength in the center of the magnetic field coil 21 of about 0.3 m Tesla / A current flow generated.

In order to ensure a significant increase in the plasma generation efficiency and adequate magnetic guidance of the inductively coupled plasma 14, magnetic field strengths of 10 mT to 100 mT, for example 30 mT, are required. This means that the power supply unit 23 provides current strengths of approximately 30 to 100 amperes at least during the etching steps for etching a substrate 10.

Instead of the magnetic field coil 21, a permanent magnet can also be used. Such a permanent magnet advantageously does not require any energy, but has the disadvantage that it is not possible to set the magnetic field strength, which is advantageous for setting an optimal etching process. In addition, the field strength of a permanent magnet is temperature-dependent, so that the magnetic field coil 21 is preferred.

In any case, it is important that the direction of the magnetic field generated via the magnetic field coil 21 or the permanent magnet is at least approximately or predominantly parallel to that through the connecting line of substrate 10 and inductively coupled plasma 14 or the

Plasma excitation zone is defined direction (longitudinal magnetic field orientation).

A further advantageous embodiment of the exemplary embodiment explained provides that, in order to improve the uniformity of the etching process, an aperture known from DE 197 34 278 inside the reactor 15 concentric with the reactor wall between the ICP source 13 or the plasma excitation zone and the substrate 10 is attached. This aperture is in Figure 1 for the sake of

Clarity not shown. It is preferably attached to the spacer 22 (“spacer”) about 5 cm above the substrate electrode 11 or the substrate 10.

In addition, if a magnetic field coil 21 is used, a suitable, known monitoring device must be integrated into the power supply unit 23, which is integrated into the process sequence control and monitors the coil temperature and performs an emergency shutdown, for example in the event of cooling water failure.

The ICP coil generator 17 continues to couple a pulsed plasma power into the inductively coupled plasma 14 during the etching steps and / or during the passivation steps, which average time is between a minimum of 300 watts and a maximum of 5000 watts. Preferably, 2000 watts are coupled in during the etching steps on average and 500 watts during the passivation steps.

In order to enable the pulsing of the injected plasma power, it is further provided that during the pulsing the impedance of the high-frequency power generated by the ICP coil generator 17 is continuously adapted to the plasma impedance that changes with changing, ie pulsed plasma power. For this purpose, the frequency of the high-frequency alternating electromagnetic field, which the ICP coil generator 17 generates, is varied within a predetermined bandwidth for impedance matching.

In detail, the matching network, which is preferably constructed symmetrically and feeds the ICP source 13 symmetrically, is initially set in the second impedance transformer 18 in such a way that the best possible impedance matching is always given when the coupled-in high-frequency plasma power pulses have reached their maximum values. Typical maximum values of the high-frequency plasma power pulses are between

3 kWatt and 20 kWatt with a pulse-to-pause ratio of 1: 1 to 1:10.

It is further provided that the frequency variation of the coupled electromagnetic alternating field takes place such that when the maximum values of the high-frequency plasma power pulses are reached, the stationary or resonant frequency 1 ^{λ λ} of the high-frequency alternating electromagnetic field generated by the ICP coil generator 17 is reached. The stationary frequency 1 ^{, Λ is} preferably 13.56 MHz.

The variation of the frequency of the electromagnetic alternating field around the stationary frequency 1 ^xx when pulsing the plasma power is carried out to ensure that when pulsing the plasma power always an at least extensive adaptation of the impedance of the generated high-frequency power or the ICP coil generator 17 to the respective, itself temporal as a function of plasma performance changing impedance of the plasma 14 is given. For this purpose, the frequency of the ICP coil generator 17 is released within a certain bandwidth around the stationary frequency 1 ^{λ λ} and varied within this bandwidth by control electronics for impedance matching.

This frequency variation is explained with the aid of FIG. 3, in which a filter characteristic curve 1 ^{Λ is} shown, which specifies a preset frequency range (bandwidth) within which the frequency of the ICP coil generator 17 is varied, each frequency having a certain high-frequency power or plasma power to be coupled in or a damping A is assigned to the power of the ICP coil generator 17. The frequency to be achieved in the stationary case is

Stationary frequency l ^{, λ} , which is at least approximately present when the respective maximum power of the pulse is reached during a plasma power pulse.

Further details of a suitable electronic circuit for impedance matching by frequency variation in the form of an automatically acting feedback loop are explained with the aid of FIG. 2. First, the ICP source 13, ie specifically its coil, is initially fed in a manner known per se from DE 199 00 179 through a preferably balanced symmetrical matching network 2 from an unbalanced asymmetrical output of the ICP coil generator 17. The matching network 2 is part of the second impedance transformer 18. The ICP coil generator 17 also has a high-frequency power amplifier 3 and a quartz oscillator 4 for generating a high-frequency fundamental with a fixed frequency of, for example, 13.56 MHz. The high-frequency fundamental oscillation of the quartz oscillator 4 is normally fed into the amplifier input of the power amplifier 3 in the prior art. However, this feed is first modified in such a way that the quartz oscillator 4 from the amplifier input of the power amplifier 3 at least during the

Power change phases separately and the input of which is made accessible externally, for example via a corresponding input socket. Since the quartz oscillator 4 no longer has a function in this embodiment, it can also be suitably deactivated.

It is also possible to use the quartz oscillator 4 in the stationary case, i.e. after completion of a power variation, switch back to the amplifier input and disconnect the external feedback loop.

This is a very quickly possible electrically

Switch between internal oscillator and external

Feedback loop, depending on whether the generator output power is stationary or in

Change is underway.

The power amplifier 3 also has generator control inputs 9, which are used for external control of the ICP coil generator 17, in a known manner. It is also possible, for example, to switch the ICP coil generator 17 on and off or to specify a high-frequency power to be generated for coupling into the plasma 14. In addition, generator status outputs 9 ^{λ are provided} for feedback of generator data, such as generator status, current output power, reflected power, overload, etc., to an external control device (machine control) (not shown) or the power supply unit 23 of the plasma generator 5. The amplifier input of the power amplifier 3 is now connected in the sense of a feedback circuit at least temporarily, ie during power change phases, to the ICP source 13 via a frequency-selective component 1. In addition, capacitors, inductors and resistors or combinations thereof can be connected and provided in a manner known per se as a voltage divider, in order to convert the high voltages that occur at the coil of the ICP source 13 to an input variable for the frequency-selective component 1 or to weaken the amplifier input of the power amplifier 3 suitable dimension. Such voltage dividers are state of the art and are only indicated in FIG. 2 by a coupling-out capacitor 24 between the coil of the ICP source 13, ie a signal tap 25 and the frequency-selective component 1. Incidentally, the signal tap 25 can alternatively also be moved into the vicinity of the grounded center or center tap 26 of the coil of the ICP source 13, where correspondingly lower voltage levels prevail. Depending on the distance of the signal tap 25, which can be designed, for example, as an adjustable clamping contact, from the grounded center tap 26 of the coil of the ICP source 13, a greater or lesser tapped voltage can be set and favorable level relationships can thus be achieved.

The frequency-selective component 1 is shown as an example as a tunable arrangement of coils and capacitors, so-called LC resonance circuits, which together form a bandpass filter. This bandpass filter has a certain predetermined bandwidth as a passband of, for example, 0.1 MHz to 4 MHz and a filter characteristic curve ^λ , as is shown schematically in FIG. In particular, the bandpass filter has a resonance or stationary frequency 1 ^{, Λ} with maximum signal transmission. This stationary frequency 1 ^{λ λ} amounts to 13.56 MHz in the example explained and can in particular be an additional one with a quartz crystal 6 or a piezoceramic filter element

Component of the bandpass filter can be precisely defined. In addition, it is also possible to combine so-called piezoceramic filter elements or other frequency-selective components known ^{per se} to form a ^bandpass filter with a desired filter characteristic, bandwidth and stationary ^{frequency λλ} instead of LC resonance circuits.

The arrangement described above of regulated power amplifier 3, matching network 2, ICP source 13 and band filter represents a feedback circuit in the manner of a Meissner 'see oscillator. This oscillates during operation first in the vicinity of the stationary frequency 1 ^{Λ λ} in order to focus on one to rock out the predetermined output power of the power amplifier 3. The phase relationship between the generator output and the signal tap 25 required for the oscillation is previously set once, for example via a delay line 7 of defined length and thus via a phase shift defined by the signal transit time or a phase shifter known per se instead of the delay line 7. This always ensures that the coil of the ICP source 13 is optimally evaporated with a correct phase.

Via the delay line 7 it is further ensured that at the location of the ICP source 13 the driving electrical voltage and the current in the coil of the ICP source 13 have a resonance phase of approximately 90 ° to one another. In practice, the resonance condition of the feedback circuit via the frequency-selective component 1 is otherwise not sharp, so that in many cases a slight frequency shift in the vicinity of the resonance or stationary frequency l ^{, λ is} sufficient to quasi automatically correct the resonance condition with regard to the phase. It is therefore sufficient to only approximately correct the resonance condition by the external wiring so that the resonance circuit swings up somewhere in the immediate range of its stationary frequency l ^λ .

However, should all the phase shifts from the signal tap 25 of the coil of the ICP source 13 through the bandpass filter into the input of the power amplifier 3 and through the power amplifier to the second

Adding impedance transformer 18 back into the coil of ICP source 13 so unfavorably that vaporization takes place instead of vaporization of the resonance circuit, so the system cannot oscillate. The feedback then becomes an undesirable negative feedback instead of the desired positive feedback. The setting of this phase, which is at least approximately correct, is carried out by the delay line 7, the length of which is therefore to be set once for the plasma generator 5 so that the feedback has a constructive effect, that is to say it has an evaporation effect.

Overall, in the event of a mismatch to the plasma impedance, for example during rapid changes in power, the explained feedback loop can be located within the pass band of the bandpass filter

Dodge frequency and thus always maintain a largely optimal impedance matching even with rapid changes in impedance of the inductively coupled plasma 14. During such rapid changes in performance is the one explained Feedback loop always activated and the internal oscillator 4 of the generator 17 deactivated.

As soon as the inductively coupled plasma 14 then stabilizes with regard to the plasma impedance or the coupled plasma power, the frequency of the ICP coil generator 17 will return to near or to the value of the maximum pass frequency, which is given by the stationary frequency 1 ^{, Λ} . This adaptation of the impedance by frequency variation takes place automatically and very quickly within a few oscillation periods of the high-frequency alternating voltage generated by the ICP coil generator, ie in the microsecond range.

The connection between the output of the power amplifier 3 and the input of the second impedance transformer 18 is otherwise provided by the line 8, which is designed as a coaxial cable and is capable of carrying a power of a few kWatt.

In order to couple a pulsed plasma power into the inductively coupled plasma, the output power of the ICP coil generator 17 is switched on and off, for example, periodically with a repetition frequency of typically 10 Hz to 1 MHz, preferably 10 kHz to 100 kHz. pulsed.

Alternatively, the amplitude of the Hull curve of the output voltage of the ICP coil generator 17 can be modulated with a suitable modulation voltage. Such devices for amplitude modulation are well known from high frequency technology. For this purpose, the generator control input 9 is used, for example, to set the target value for the high-frequency power of the ICP Coil generator 17 is used to feed the signal that modulates the high-frequency power of the ICP coil generator 17.

Of course, the ICP coil generator 17 and the other affected components of the plasma generator 5 when pulsing the plasma power must be designed so that they can handle the peak loads (current and voltage peaks) without damage. Due to the high voltage peaks at the inductive coil, the balanced supply of the ICP source 13 has a particularly advantageous effect on the maintenance of favorable plasma properties.

Typical pulse-to-pause ratios, i.e. the ratio of the time duration of the pulses to the time duration of the pulse pauses in the plasma etching process with pulsed plasma power explained is otherwise between 1: 1 and 1: 100. The amplitude of the individual high-frequency power pulses for generating the plasma power pulses is expediently between 500 watts and 20,000 watts, preferably approximately 10,000 watts, the mean plasma power being set, for example, by adjusting the pulse-to-pause ratio.

A further exemplary embodiment provides in a continuation of the exemplary embodiment explained above that the magnetic field generated via the magnetic field coil 21 is now also pulsed. However, it should be emphasized that the use of a constant or pulsed magnetic field is advantageous for the method according to the invention for plasma etching with plasma power pulses, but is not essential. Depending on the individual case, an additional magnetic field can also be dispensed with. The pulsation of the magnetic field, which is produced in a simple manner via corresponding current pulses generated by the power supply unit 23, is particularly preferably carried out in such a way that the magnetic field is only generated when a high-frequency power pulse for generating or coupling plasma power into the inductively coupled plasma is also generated at the same time 14 is pending at the ICP source 13. As long as no plasma power is coupled in or no plasma is excited, no magnetic field support is usually required.

Such a temporal synchronization of high-frequency power pulses for coupling plasma power into the plasma 14 and current pulses through the magnetic field coil 21 is explained with the aid of FIG. 4. The coil current through the magnetic field coil 21 is switched on shortly before a high-frequency power pulse and switched off again shortly after the end of this pulse. The temporal synchronization of the current or plasma power pulses can be ensured in a simple manner by means of a pulse generator known per se, for example integrated into the power supply unit 23, which is provided with additional timing elements in order to provide the plasma power pulse with a certain delay of, for example, 10% of the set one

High frequency pulse duration after switching on the current of the magnetic field coil 21 or this current with a certain delay of, for example, 10% of the set high frequency pulse duration after the end of the

Switch off the plasma power pulse again. For this purpose, a connection between the power supply unit 23 and the ICP coil generator 17 is also provided. Such synchronization circuits and corresponding timers for Production of the time delays required are state of the art and generally known. For this purpose, the power supply unit 23 is further connected to the ICP coil generator 17. It should also be emphasized that the duration of a current pulse through the magnetic field coil 21 is advantageously always somewhat longer than the duration of a plasma power pulse.

Typical repetition rates or pulse rates are based on the inductance of the magnetic field coil 21, which

Rate of change of the coil current is limited. A repetition rate of a few 10 Hz to 10 kHz, depending on their geometry, is realistic for most magnetic field coils 21. Typical pulse-to-pause ratios for the plasma power pulses are between 1: 1 and 1: 100.

In this context, it is further provided to use the aperture known from DE 197 34 278.7 and already explained above below the magnetic field coil 21 a few cm above the substrate 10 or the substrate electrode 11 which carries the substrate 10. This aperture on the one hand significantly improves the uniformity of the etching across the substrate surface, in particular with a symmetrically fed ICP source 13. At the same time, it also reduces the time-variable magnetic field - the transients - at the location of the substrate 10.

Eddy currents in the aperture ring of the aperture lead to an evaporation of the time-variable magnetic field components immediately in front of the substrate 10, so that induction processes on the substrate 10 itself are weakened.

Such changing magnetic fields, so-called transients, could induce voltages on antenna structures on the substrate 10, which in turn can lead to damage to the substrate 10 if it does so for example, has integrated circuits or in particular field effect transistors.

A further exemplary embodiment provides, in a continuation of the above exemplary embodiments, that in addition to the pulsing of the plasma power via the ICP coil generator, if appropriate as explained above with simultaneous use of a temporally constant or pulsed magnetic field, now also the one applied to the substrate 10 via the substrate electrode 11. of the

High voltage power generated by the substrate voltage generator 12 is pulsed, and that these pulsations of plasma power and substrate voltage or of plasma power, substrate voltage and magnetic field are in particular synchronized with one another.

In particular, the pulsing of the pulsed high-frequency power coupled into the substrate electrode 11 preferably takes place in such a way that high-frequency power is coupled into the substrate 10 via the substrate voltage generator 12 only during the duration of the plasma power pulses generated via the ICP coil generator 17. For this purpose, for example, one or more high-frequency power pulses with the substrate voltage generator 12 during one

Plasma power pulse, i.e. at maximum plasma density of positively charged ions and electrons.

Alternatively, the pulsing of the high-frequency power coupled into the substrate electrode 11 can, however, also take place in such a way that one or more

Substrate voltage generator pulses are only applied during the pulse pauses of the plasma power pulses. In this case, the one coupled in via the substrate voltage generator High-frequency power is coupled in when the plasma generation is not active, i.e. with a minimum density of positively charged ions and electrons, but a maximum density of negatively charged ions, so-called anions, which result from the recombination of electrons and

Neutral particles are created in the breakdown of excitation in the collapsing plasma. These time phases of a plasma just switched off, the so-called "afterglow regime", i.e. the "afterglow phase" of the plasma just switched off are dominated by recombination processes of electrons and positively charged ions or neutral particles. If in this afterglow phase the

If substrate electrode power is activated in the form of one or more pulses, this leads to desirable wafer effects on the substrate 10 to be processed in certain applications, such as, for example, in the case of an etch stop on a buried dielectric such as SiO ₂ with a simultaneously high aspect ratio of the trench trench produced, which in particular caused by the increased exposure to negatively charged ions, which otherwise

Plasma etching processes play practically no role. A particularly advantageous, in this context, special implementation of this temporal correlation of plasma power pulses and high-frequency power pulses coupled into the substrate electrode 11 is provided in that the plasma generation takes place essentially in a continuous wave and is only switched off briefly in each case in order to within this short switch-off pause of the ICP coil generator 17 to couple a high-frequency power pulse into the substrate 10 via the substrate voltage generator 12. Overall, the ICP coil generator 17 is thus periodically briefly interrupted with the repetition frequency of the appearance of the substrate voltage generator pulses for a period of time that is longer, in particular slightly longer than the pulse duration of the

Substrate voltage generator pulse is. In this case, the pulse-to-pause ratio of the ICP coil generator 17 is typically 1: 1 to 20: 1.

Depending on the specific etching process, there are a multitude of further possibilities for temporal synchronization or correlation of high-frequency power pulses coupled into the substrate 10 via the substrate voltage generator 12 and plasma power pulses coupled into the inductively coupled plasma 14. The substrate voltage generator pulses can thus be coupled in both during the plasma power pulses and during the plasma power pauses, i.e. for example, one substrate voltage generator pulse is generated during a plasma power pulse and another during a plasma power pause

Substrate voltage generator pulse set. The ratios of the pulse numbers of the substrate voltage generator 12 in the phases “plasma on” and “plasma off” can be chosen largely freely in individual cases.

Another possibility is to use the substrate voltage generator pulses only during falling and / or rising pulse edges of the plasma power pulses, ie when the "afterglow phase" begins or when the plasma generation starts up. The optimum correlation of plasma power pulses and substrate voltage generator pulses in each case must be determined by the person skilled in the art in individual cases for the respective etching process or the respectively etched substrate on the basis of simple test statutes. The temporal synchronization or correlation of the high-frequency power pulses coupled into the substrate 10 via the substrate voltage generator 17 with the plasma power pulses is very particularly preferably such that the pulse duration of the

High-frequency power pulses are set so short that a single pulse only lasts a few oscillation periods, in particular less than 10 oscillation periods, of the high-frequency fundamental oscillation of the high-frequency alternating voltage generated in the substrate voltage generator.

Specifically, for example, a frequency of 13.56 MHz is used for the basic oscillation of the high-frequency power pulses to be coupled into the substrate, so that the duration of one oscillation period of the high-frequency basic oscillation is approximately 74 ns. In the case of 10 oscillation periods, this results in a pulse duration of the substrate voltage generator pulses of only 740 ns. Thus, at a repetition frequency of the individual pulses of the substrate voltage generator pulses of, for example, 200 kHz, corresponding to a pulse interval of 5000 ns, and a pulse length of, for example, 500 ns, i.e. approximately 7 oscillation periods of the high-frequency fundamental of 13.56 MHz, a pulse-to-pause ratio of 1: 9 set. To achieve an average of approximately 20 watts, which is coupled into the substrate 10

High-frequency power therefore requires a maximum power of the substrate voltage generator pulses of 200 watts, which is obtained via correspondingly large high-frequency amplitudes.

The maximum performance of each

However, substrate voltage generator pulses can also be much lower or much higher, for example up to Reach 1200 watts. The high-frequency power coupled into the substrate 10 on average over time then amounts in the illustrated example to one tenth of the respective maximum value of the individual pulses.

In addition to the choice of the pulse-to-pause ratio, the maximum value of the power of an individual substrate voltage generator pulse is thus available as a parameter for setting the high-frequency power coupled into the substrate 10 over time. Therefore, either the maximum power during the

Substrate voltage generator pulses are set to a fixed value of, for example, 1 kWatt and the pulse-to-pause ratio is regulated in such a way that a preset mean value of the high-frequency power in the

Substrate 10 is coupled, or vice versa, the pulse-to-pause ratio is fixed and the maximum power during the substrate voltage generator pulses are regulated accordingly so that this temporal average power value is reached.

To implement this regulation, for example, a setpoint specification of the high-frequency power to be coupled into the substrate 10 of the machine control of the plasma generator 5 is converted into an analog voltage quantity

Repetition frequency of individual pulses implemented so that the average power output from the substrate voltage generator 12 and reported back to the machine controller corresponds exactly to the setpoint value as a time average. To translate an analog voltage specification into a frequency, known so-called V / f converter construction systems (voltage / frequency converters) or VCOs ("voltage controlled oscillator") are used. The generation of high-frequency pulses in the specified short-term range with the substrate voltage generator 12 is per se technically relatively unproblematic, since high-frequency generators are commercially available which have a rise and fall time of 30 ns and can handle pulse durations of 100 ns at peak powers up to several kilowatts.

The explained, coupled into the substrate 10 and generated with the substrate voltage generator 12

In order to improve reproducibility, high-frequency power pulses in the range of a few hundred nanoseconds are preferably generated in such a way that the high-frequency signal always looks the same within a single pulse. For this purpose, for example, three full high-frequency oscillation periods of the 13.56 MHz basic oscillation are always cut out for an individual pulse so that the high-frequency signal curve begins at the beginning of each individual pulse with a zero crossing and an increasing sine and at the end of the

Single pulse ends with a zero crossing and also an increasing sine.

This synchronization of the individual pulse curve and the course of the high-frequency basic oscillation can alternatively also take place in such a way that a positive sine half-wave of the high-frequency basic oscillation begins at the beginning of a single pulse and a positive half-wave ends at the end of an individual pulse, i.e. the single pulse comprises a larger number of positive ones Half sine waves as negative half sine waves. Conversely, a corresponding number of negative sine half-waves as positive sine half-waves can be combined into one by corresponding synchronization under otherwise identical conditions Single pulse can be placed by the single pulse begins and ends with a negative sine half-wave of the high-frequency signal.

Without the synchronization described, the number of positive and negative sine half-waves in the generated high-frequency pulses could be different, with differences of up to two sine half-waves being possible in limit cases. This led especially with a small number of oscillation periods within one over the

Substrate voltage generator 17 generated high-frequency pulse to stochastic deviations in the signal curves of the individual pulses and in particular to slowly fluctuating conditions with regard to the number of positive and negative sine half-waves, which negatively affects the reproducibility of the entire etching process.

In order to ensure that the same high-frequency voltage curve is always present within a single pulse of the substrate voltage generator 12, the electronic circuit explained with the aid of FIG. 5 is preferably additionally integrated with the substrate voltage generator 12 in this exemplary embodiment in order to synchronize the individual pulses with the high-frequency fundamental oscillation.

In detail, the circuit according to FIG. 5 initially provides a control device 32 with an integrated frequency generator, which specifies a square-wave signal with the frequency with which the individual pulses are to be coupled into the substrate 10, for example 200 kHz. However, this repetition frequency can alternatively also - from the setpoint specification - with a permanently preselected pulse peak power of the substrate voltage generator 12 an average power of the system control of the plasma set 5 are derived in such a way that the average power given by the substrate voltage generator 12 in the form of individual pulses and reported back to the machine control as the setpoint

Average power corresponds to what is achieved, for example, by a simple voltage-frequency conversion with appropriate calibration.

The square wave output voltage of the frequency generator

In the following, control device 32 is then first converted into an assigned frequency in a U / f converter device 34 known per se and at the same time applied to the D input and the clear input (CLR input) of a D flip-flop 35. The D flip-flop 35 thus remains erased (O level at Clear) and cannot be set (O level at D input) as long as the square wave voltage is at an O level.

At the clock input of the D flip-flop 35, an oscillator voltage of a high-frequency generator 31, which is suitably prepared under certain circumstances, is applied via an adjustable phase shifter 30 and generates a high-frequency AC voltage of, for example, 13.56 MHz. In the case of commercially available HF generators, this output is referred to as the CEX output (“common exciter”).

As soon as the square-wave signal of the frequency generator has changed from 0 to 1, the D flip-flop 35 is set each time by the next, subsequent positive sine half-wave of the high-frequency AC voltage of the RF generator 31 and remains set until the square-wave signal of the frequency generator goes from 1 to 1 again 0 switches back and resets the D flip-flop 35 by means of the O level via the clear input.

The output of the D flip-flop 35 is further connected to the clock input of a monoflop 33 in such a way that the monoflop 33 simultaneously emits a single pulse when the D flip-flop 35 is set, the pulse duration of which is largely via a resistor-capacitor combination integrated in the monoflop 33 free, especially very short ie less than 100 ns can be selected. This single pulse of

Monoflops 33 are fed to the pulse input of the high-frequency generator 31 and, during the duration of the single pulse applied to the generator output 36, causes a high-frequency output pulse, i.e. one consisting of a few high-frequency oscillation periods

Submit voltage package. Thus, the output signal at the generator output 36 is always synchronous with the high-frequency fundamental oscillation of the internal high-frequency generator 31, so that the output signal of the substrate voltage generator 12 at the output 36, i.e. the substrate voltage generator pulses generated and coupled in via the substrate 10 always look the same.

The combination of D flip-flop 35 and monoflop 33 described guarantees that per square period of

Frequency generator only a single pulse of a selected duration is generated, which is synchronized to the high-frequency AC voltage of the high-frequency generator 31. The substrate voltage generator thus generates 12 output pulses of adjustable duration and always the same

Signal waveform, which are synchronized to the high-frequency fundamental of the high-frequency generator 31. The phase shifter 30 between the CEX output of the high-frequency generator 31 and the clock input of the D flip-flop 34 makes it possible to vary the phase position of the high-frequency oscillation periods contained in each individual pulse or output pulse of the high-frequency generator 31 within the pulse width. The phase shifter can thus be adjusted in particular so that the high-frequency oscillation periods of the alternating voltage begin with the onset of the output pulse of the substrate voltage generator 12 and with the

Decay of this output pulse ends, so that each output pulse comprises just a whole number of oscillation periods or sine half-waves. In the simplest case, the phase shifter 30 is a coaxial cable of a defined length as a delay line.

The circuit described in FIG. 5 is merely an example. In their place, other devices, for example a synchronous divider, which divides the frequency of the generator-internal oscillator and derives individual pulses and pauses between the individual pulses, can also be used.

The advantageous effect of the, in particular, very short, high-frequency, high-amplitude high-frequency power pulses used in the above exemplary embodiments, which are coupled into the substrate 10 via the substrate voltage generator 12, is based on the following mechanisms in the plasma 14:

As is known, a negative is produced on a substrate electrode 11 which is exposed to a plasma 14 and to which a high-frequency voltage or high-frequency power is applied via the substrate voltage generator 12 DC voltage against the plasma 14 and against earth potential. This direct voltage, called "bias voltage" or "self-bias", results from the different mobility of electrons and positive ions in the alternating electric field. While the light ones

Electrons instantaneously follow the high-frequency alternating field and can very easily reach the substrate electrode 11 during the positive half-waves of the alternating voltage, this is less and less possible for the much heavier positive ions during the negative half-waves of the alternating voltage with increasing frequency of the alternating electrical field. As a result, the substrate electrode 11 is negatively charged by the excess of incoming electrons compared to the incoming positive ions until the charge becomes saturated and, on average, as many electrons as positively charged ions reach the substrate electrode 11. The substrate electrode voltage corresponds to this saturation value of the negative charge.

To explain this effect, FIG. 6 shows a simple electrical equivalent circuit diagram for a substrate electrode surface element 37 which is exposed to a plasma 14 and is supplied with a high-frequency power from the substrate voltage generator 12. The coupling to earth takes place via the plasma 14, which results from the parallel connection of resistor R and diode D is symbolized. The diode D takes into account the effect of self-rectification through the different mobility of electrons and ions in the plasma 14, the resistance R of the

Energy dissipation into plasma 14 (effective resistance). The capacitance C (reactance) is essentially an apparatus constant of the structure of the substrate electrode 11. In pulse operation using high-frequency substrate voltage generator pulses, a substrate electrode voltage builds up on the substrate electrode 11 at the beginning of each pulse, which after a number of high-frequency oscillation periods reaches a saturation value and remains there until the end of the pulse. After the end of the high-frequency oscillation package, this substrate electrode voltage then decays again during the pulse pause due to discharge processes. A typical number of oscillation periods, which is required to achieve a stationary substrate electrode voltage, is at a high frequency of 13.56 MHz and a high-density inductively coupled plasma 14, which is in contact with the substrate electrode, at about 20 to 100 oscillation periods.

By using very short individual pulses, which comprise only a few oscillation periods, preferably less than 10 oscillation periods, the saturation value of the substrate electrode voltage has not yet been reached and the

Substrate electrode voltage still rising. This is explained in FIG. 7, which shows how the substrate _{electrode voltage} U _{Bιas develops} as a function of the number of oscillation periods n of the fundamental oscillation of the high-frequency AC voltage (13, 56 MHz) coupled into the substrate 10.

The level of local voltage ultimately reached in the event of saturation after many oscillation periods depends essentially on the effective resistance R (energy dissipation into the plasma) and the capacitance C of the capacitor

(Reactive power component) according to FIG. 6. The saturation value of the substrate electrode voltage, which occurs after many oscillation periods on the substrate surface, thus depends to a large extent on the plasma resistance R (see FIG. 6), ie on the energy dissipation into the plasma 14, which, however, is generally inhomogeneous laterally across the substrate 10.

Local differences with regard to the energy dissipation into the plasma 14 thus occur, for example, between the center and edge of a substrate 10, which leads to voltage gradients between different surface areas of the substrate 10. These voltage gradients are further strengthened by the fact that the surface of the substrate 10 is at least partially electrically insulating or only slightly conductive during etching due to the frequently used dielectric masking layers (photoresist, SiO mask, etc.).

In this respect, due to the effects explained, the substrate surface 10 no longer represents an equipotential surface, but rather occurring voltage gradients from the center of the substrate to the edge of the substrate act as an electrical lens with respect to the plasma 14, which ultimately leads to a deflection of the ions accelerated to the substrate 10 from the vertical and thus to interference in the generated etching profiles leads.

Due to the very short used

Therefore, a substantial homogenization of the substrate electrode voltage across the substrate surface is achieved regardless of possibly different spatially different plasma resistances R. This is illustrated in FIG. 7 by the linear curve shape in the case of only a small number of oscillation periods n. Overall, the measures explained thus achieve a drastic reduction in voltage gradients on the Substrate surface, a loss of the undesirable electrical lens effect and finally to significantly reduced profile slopes, for example in trench trenches structured out of the substrate.

Furthermore, it is ensured by relatively long pulse pauses after each relatively short individual pulse that a previously reached negative substrate electrode voltage is at least largely reduced again. Each substrate electrode power pulse thus starts from an identical, defined, discharged initial state of the substrate surface.

By pulsing the substrate electrode power described, only a fraction of the

Reached substrate electrode voltage, which otherwise, i.e. when the saturation value is reached after many

Would set oscillation periods. Therefore, if high or very high substrate electrode voltages of, for example, 20 volts to 100 volts on average are to be realized, they must be correspondingly large

High-frequency peak performances are operated during the individual impulses.

LIST OF REFERENCE NUMBERS

1 frequency-selective component 1 'filter characteristic

1 ^{Λ Λ} Stationary frequency

2 matching network

3 power amplifier

4 quartz oscillator 5 plasma set

6 quartz crystal

7 delay line

8 line

9 Generator control input 9 ^Λ Generator ^status output

10 substrate

11 substrate electrode

12 substrate voltage generator 13 ICP source

14 inductively coupled plasma

15 reactor

16 first impedance transformer

17 ICP coil generator 18 second impedance transformer

19 gas supply

20 gas removal

21 magnetic field coil 22 spacer

23 power supply unit

24 decoupling capacitor

25 signal tap

26 center tap 30 phase shifter 31 high-frequency generator 32 control device 33 monoflop 34 U / f converter device 35 D flip-flop 36 generator output 37 substrate electrode surface

10

Claims

claims

1. Device for etching a substrate (10), in particular a silicon body, by means of an inductively coupled plasma (14), with an ICP source (13) for generating a high-frequency alternating electromagnetic field and a reactor (15) for generating the inductively coupled plasma (14) from reactive particles by exposure to the high-frequency electromagnetic

Alternating field to a reactive gas, characterized in that a first means is provided with which plasma power pulses to be coupled into the inductively coupled plasma (14) can be generated with the ICP source (13).

2. Device according to claim 1, characterized in that the first means is an ICP coil generator (17) which generates a pulsed radio frequency power which is variably adjustable with respect to the pulse-to-pause ratio of the plasma power pulses and / or the individual pulse power.

3. Apparatus according to claim 2, characterized in that an impedance transformer (18) is provided in the form of an especially balanced symmetrical matching network for adapting an output impedance of the ICP coil generator (17) to a plasma impedance dependent on the individual pulse power of the plasma power pulses to be injected.

4. The device according to claim 3, characterized in that the impedance transformer (18) is preset such that at a predetermined maximum individual pulse power in the inductively coupled plasma (14) to be coupled plasma power pulses in the staionary power case an at least largely optimal impedance matching is ensured.

5. Apparatus according to claim 2, characterized in that in the ICP coil generator (17) components are integrated which make an impedance matching as a function of the single pulse power to be coupled in by varying the frequency of the electromagnetic alternating field generated.

6. The device according to claim 5, characterized in that the ICP coil generator (17) is provided with an automatically acting feedback circuit with a frequency-selective component (1), the feedback circuit at least one regulated

Power amplifier, a frequency-selective band filter with a stationary frequency (1 ") to be achieved and a delay line (7) or a phase shifter.

7. The device according to at least one of the preceding claims, characterized in that a second means is provided which between the substrate (10) and the ICP source (13) generates a static or time-varying, in particular pulsed magnetic field.

8. The device according to claim 7, characterized in that the first means is a magnetic field coil (21) with associated power supply unit (23) or a permanent magnet, wherein the magnetic field coil (21) generated magnetic field by means of the power supply unit (23) can be varied in time, in particular can be pulsed.

9. The device according to claim 1, characterized in that a substrate voltage generator (12) is provided, with which the substrate (10), in particular the substrate (10) arranged on a substrate electrode (11), with a continuous or time-varying, in particular pulsed High frequency power can be applied.

10. The device according to claim 9, characterized in that for impedance matching between the

Substrate voltage generator (12) and the substrate (10) a first impedance transformer (12) is provided.

11. The device according to at least one of the preceding claims, characterized in that the ICP coil generator (17) with the substrate voltage generator (12) and / or the power supply unit (23) is connected.

12. A method for etching a substrate (10), in particular a silicon body, with a device according to at least one of the preceding claims, characterized in that at least temporarily a pulsed

High-frequency power is coupled as pulsed plasma power into the inductively coupled plasma (14).

13. The method according to claim 12, characterized in that the pulsed plasma power via an ICP source (13) is coupled in with a high-frequency electromagnetic alternating field with a constant frequency or with a within a frequency range a stationary frequency (l ^Λ ) varying frequency is applied.

14. The method according to claim 12, characterized in that the pulsed high-frequency power is generated with an ICP coil generator (17) having a frequency of 10 Hz to 1 MHz and a pulse-to-pause ratio of 1: 1 to 1 : 100 operated pulsed.

15. The method according to claim 12, characterized in that a plasma power of 300 watts to 5000 watts is injected into the inductively coupled plasma (14) on average, and that the generated individual pulse powers of the high-frequency power pulses between 300 watts and 20 kWatt, in particular 2 kWatt up to 10 kWatt.

16. The method according to claim 12 or 13, characterized in that the pulsing of the coupled-in high-frequency power is accompanied by a change in the frequency of the coupled-in high-frequency power, the frequency change being controlled in such a way that the pulsed into the inductively coupled plasma (14) is coupled Plasma performance is maximized.

17. The method according to at least one of claims 12 to 16, characterized in that a static or time-varying, in particular periodically varying or pulsed magnetic field is generated during the etching, the direction of which is at least approximately or predominantly parallel to a through the connecting line of the substrate (10 ) and inductively coupled plasma (14) defined direction.

18. The method according to claim 17, characterized in that the magnetic field is generated such that it extends into the region of the substrate (10) and the inductively coupled plasma (14) and inside the reactor (15) an amplitude of the field strength between 10 mTesla and 100 mTesla.

19. The method according to claim 17 or 18, characterized in that via the power supply unit (23) a pulsed with a frequency of 10 Hz to 20 kHz

Magnetic field is generated, the pulse-to-pause ratio when pulsing the magnetic field is between 1: 1 and 1: 100.

20. The method according to at least one of the preceding claims, characterized in that the substrate (10) via a substrate voltage generator (12) with a constant or time-variable, in particular pulsed high-frequency power is applied.

21. The method according to claim 20, characterized in that the pulse duration of the high-frequency power coupled into the substrate is between 1 times and 100 times, in particular 1 times and 10 times, the oscillation period of the high-frequency fundamental oscillation of the high-frequency power.

22. The method according to claim 20 or 21, characterized in that the high-frequency power acts on the substrate (10) with a temporal average power of 5 watts to 100 watts, the maximum power of a single high-frequency power pulse being 1 to 20 times, in particular the 2nd -fold to 10 times the time average power.

23. The method according to claim 21, characterized in that the frequency of the coupled high-frequency power between 100 kHz to 100 MHz, in particular 13.56 MHz, and that the pulse-to-pause ratio of the coupled high-frequency power pulses between 1: 1 and 1 : 100, especially 1: 1 and 1:10.

24. The method according to at least one of the preceding claims, characterized in that the pulsing of the coupled plasma power and the pulsing of the high-frequency power coupled into the substrate (10) via the substrate voltage generator (12) or the pulsing of the magnetic field, the pulsing of the coupled plasma power and that Pulses of the high-frequency power coupled into the substrate (10) via the substrate voltage generator (12) are correlated or synchronized with one another in time.

25. The method according to claim 24, characterized in that the correlation is carried out in such a way that the magnetic field is first applied before a high-frequency power pulse of the ICP coil generator (17), and that the magnetic field is switched off again after this high-frequency power pulse has subsided.

26. The method according to claim 24 or 25, characterized in that the correlation takes place in such a way that during a high-frequency power pulse of the ICP coil generator (17) the high-frequency power coupled into the substrate (10) via the substrate voltage generator (12) is switched off and / or that while one about the

Substrate voltage generator (12) in the substrate (10) coupled high-frequency power pulse which via the ICP Coil generator (17) coupled high-frequency power is switched off.

27. The method according to claim 24 or 25, characterized in that the synchronization takes place in such a way that the substrate (10) during the duration of a via the ICP coil generator (17) coupled into the plasma (14) plasma power pulse with the

Substrate voltage generator (12) in the substrate (10) coupled high-frequency power pulses is applied.

28. The method according to claim 24 or 25, characterized in that the correlation is carried out in such a way that the high-frequency power coupled into the substrate (10) via the substrate voltage generator (12) in each case during a power increase and / or a power drop of one via the ICP coil generator ( 17) high-frequency power pulse coupled into the plasma (14) is generated.

29. The method according to claim 24 or 25, characterized in that the correlation takes place in such a way that during the duration of the plasma power pulses coupled into the plasma (14) via the ICP coil generator (17) and during the duration of the pulse pauses of the individual via the ICP - Coil generator (17) in the plasma (14) coupled plasma power pulses, the substrate (10) is acted upon with at least one high-frequency power pulse coupled into the substrate (10) via the substrate voltage generator (12).

30. The method according to at least one of the preceding claims, characterized in that the etching in alternating etching and passivation steps are carried out at a process pressure of 5 μbar to 100 μbar.