DE102018111562A1 - Apparatus and method for determining an electrical power reflected from a plasma - Google Patents

Abstract

An apparatus for determining an electrical power reflected by a plasma, wherein the plasma is acted upon by a first high-frequency power signal having a first frequency and at least one second high-frequency power signal having at least one second frequency, the second frequency being smaller than the first frequency, the apparatus is configured to determine a first quantity which characterizes a power reflected by the plasma in the range of the first frequency and to determine a second quantity which characterizes a power reflected by the plasma in a first frequency range, the first frequency range having a prescribable number of times Summing frequencies and / or difference frequencies from the first frequency and an integer multiple of the second frequency.

Description

Field of the invention

The disclosure relates to a device for determining an electrical power reflected by a plasma, wherein the plasma can be acted upon by a first high-frequency power signal having a first frequency and at least one second high-frequency power signal having at least one second frequency, wherein the second frequency is smaller than the first Frequency.

The disclosure further relates to a corresponding method for determining an electrical power reflected by a plasma or for operating a corresponding device.

State of the art

It is known to supply conventional plasma systems, such as those used for etching processes in semiconductor manufacturing, by corresponding high-frequency generators with high-frequency energy of different frequencies ("multi-frequency systems" or "multi-frequency plasma systems"). For example, such multi-frequency systems can be supplied by a first conventional high-frequency generator having the first high-frequency power signal of the first frequency mentioned above and by a second conventional high-frequency generator having a second high-frequency power signal of the second frequency. However, the conventional high frequency generators which provide the first and second high frequency power signals for the operation of such a multi-frequency system are i.d.R. not optimized for operation in a multi-frequency system.

Description of the invention

Preferred embodiments relate to a device of the aforementioned type, wherein the device is designed to determine a first quantity, which characterizes a power reflected by the plasma in the range of the first frequency and to determine a second quantity which is one of the plasma characterized reflected power in a first frequency range, wherein the first frequency range has a predetermined number of sum frequencies and / or difference frequencies of the first frequency and an integer multiple of the second frequency. By a "power reflected by the plasma", it may be meant here both the power components which are supplied by a first generator to the plasma and from which e.g. have been reflected due to mismatching and thus get to the device, as well as those power components which have been supplied to the plasma by a second generator in which plasma has led to mixed products with the first signal and are guided by the plasma to the device.

According to investigations by the Applicant, in a multi-frequency system, nonlinearities (for example saturation effects) in the plasma result in mixed products from the high-frequency power signals of different frequencies introduced into the plasma, which are also ideal impedance matching of, for example, that high-frequency generator which generates the first high-frequency power signal in the plasma provides the first frequency to which it provided first frequency for the first high frequency generator is a "reflected power". Although the above-mentioned mixed products are only produced in the plasma when the two high-frequency power signals of different frequencies interact, they are, for example, reflected power for the first high-frequency generator. These mixed products, which are also referred to as "sidebands" can show that the plasma is excited at both frequencies, which is desirable, so are not undesirable per se, yet they produce undesirable heat loss and / or overvoltages in the first high frequency generator providing the first high frequency power signal. However, the reflected power resulting from the mixing products represents, according to the Applicant, a different loading of the first high-frequency generator than a reflected power at the first frequency, which is also referred to below as the fundamental frequency.

The principle according to the embodiments advantageously makes it possible to differentiate between a power reflected by the plasma in the range of the first frequency, that is to say the fundamental frequency, and a power reflected by the plasma in the first frequency range mentioned. The first frequency range preferably comprises at least part of the mixing products described above. In other words, the first quantity represents a power reflected by the plasma in the region of the first frequency, for example fundamental frequency, and the second variable represents a power of at least part of the said mixed products reflected by the plasma. By determining the first and second quantities, operation of the plasma of a multi-frequency system can be more accurately characterized and evaluated. Furthermore, an actual load on the first high-frequency generator or its components can be determined more precisely than in conventional systems. That increases too quite considerably the safety and reliability of such plasma systems, for example against failure, fire and destruction. It is important to consider that on the one hand, the plasma systems themselves are very complex and expensive, and this ever increasing. For example, every 1 to 2 years is expected to double the complexity of semiconductor manufacturing, causing even faster rising prices in manufacturing facilities. In addition, a failure of the systems is also very expensive, as are provided by the ever-increasing complexity more and more components on a wafer. In the event of a failure or incorrect measurement, entire wafers can be destroyed. Increasingly, this is not only undesirable, but must be ruled out with an ever-increasing probability.

Although primarily the first high-frequency generator or the application of the principle of the embodiments to the first high-frequency generator is described below, the principle of the embodiments can be transmitted alternatively or additionally to the second high-frequency generator without loss of generality. In further embodiments, it is also conceivable to apply the principle of the embodiments to multi-frequency plasma systems with more than two high-frequency generators.

In further preferred embodiments, it is provided that the first frequency range does not include the first frequency. This can ensure that the second size alone contains proportions of the mixed products, but not the first frequency.

In further preferred embodiments, it is provided that the sum frequencies can be determined as a function of the equation fs_n = f1 + n * f2, and / or that the difference frequencies can be determined as a function of the equation fd_n = f1 -n * f2, where fs_n an n-th sum frequency is, where f1 the first frequency is where n is a natural number greater than zero, where "*" is the multiplication operator, where f2 the second frequency is, and where fd_n an n-th difference frequency.

In further preferred embodiments, it is provided that the predefinable number of sum frequencies or difference frequencies is at least two, in particular at least three. Because higher order mixing products (larger values of n) have order-decreasing signal energy, in preferred embodiments it may be sufficient to consider, for example, two sum frequencies and two difference frequencies. In further embodiments, it may be provided that only a sum frequency fs_1 = f1 + f2 and a difference frequency fd_1 = f1-f2 are considered, e.g. to determine the second size from this.

Preferably, in further embodiments at least one sum frequency and at least one difference frequency are considered. Namely, according to investigations by the Applicant, mixed products of the same order but different frequency positions may each contain a different signal energy with respect to the first frequency. In these cases, this allows a precise characterization of the power reflected by the plasma in the first frequency range.

In further preferred embodiments, it is provided that the first frequency is between about 10 MHz, megahertz, and about 190 MHz, wherein in particular the first frequency has at least about one of the following values: 13.56 MHz, 27.12 MHz, 40.68 MHz, 60 MHz, 81 MHz, 161 MHz. In other embodiments, other values for the first frequency are possible.

In further preferred embodiments, it is provided that the second frequency is between about 10 kHz, kilohertz, and about 2.3 MHz, wherein in particular the second frequency has at least about one of the following values: 300 kHz, 400 kHz, 500 kHz. In other embodiments, other values for the second frequency are possible.

In further preferred embodiments in which at least one further, ie third, high-frequency generator is provided, it is possible that the high-frequency power signal generated by the third high-frequency generator has the first frequency or the second frequency or lies in a different frequency range, e.g. below the second frequency or between the first and second frequencies or above the first frequency.

In further preferred embodiments, it is provided that the device is designed to determine the first variable and / or the second variable as a function of a first signal that characterizes a voltage wave reflected from the plasma to a first high-frequency generator providing the first high-frequency power signal. This allows efficient determination of the first and second sizes. The first signal can be obtained, for example, by means of a directional coupler which connects the first high-frequency generator with, for example, a plasma chamber containing the plasma or which is arranged on a high-frequency line which connects the first high-frequency generator to the plasma chamber. In further preferred embodiments, the first high-frequency generator via a matching network ("matchbox") to be connected to the plasma chamber, which allows in a conventional manner an impedance matching of the plasma load, for example, based on the first frequency. In further preferred embodiments, a voltage and / or current extraction can be provided to determine the first signal.

In further preferred embodiments it is provided that the device is designed to transform the first signal or a signal derived therefrom by a downconversion into a second signal, wherein in particular the second signal is a baseband signal. In other words, by downconverting a frequency shift, e.g., the first signal or signal derived therefrom. subjected to smaller frequencies according to the first frequency. This enables efficient and inexpensive processing of the second signal. In further preferred embodiments, the second signal may also be an intermediate frequency signal, the down conversion thus transforming the first signal or a signal derived from the first signal into an intermediate frequency position.

In further preferred embodiments it is provided that the device is designed to mix the first signal or a signal derived therefrom with a local oscillator signal in order to obtain the second signal.

In further preferred embodiments, it is provided that the local oscillator signal has at least approximately the first frequency. Investigations by the Applicant According to it, it is sufficient if the local oscillator signal at least approximately the first frequency corresponds (a deviation of up to 2% is justifiable). An exact match of a frequency of the local oscillator signal with the first frequency is therefore unnecessary, which causes a further simplification.

In further preferred embodiments, it is provided that the device is designed to derive a third signal from the second signal by means of at least one first low-pass filtering with a first cutoff frequency, wherein in particular the device is designed to determine the first variable as a function of the third signal. The first cut-off frequency for the first low-pass filtering is preferably selected such that the third signal has only signal components which characterize a power reflected by the plasma in the range of the first frequency, but not such signal components, which are the mixed products of first frequency and second frequency belong.

In further preferred embodiments, it is provided that the first cutoff frequency is approximately less than or equal to the second frequency, preferably smaller than the second frequency. This can ensure that the third signal has only signal components which characterize a power reflected by the plasma in the range of the first frequency, and that the third signal has, in particular, no signal components associated with the mixing products.

In further preferred embodiments, it is provided that the device is designed to derive a fourth signal from the second signal by means of a second low-pass filtering with a second cut-off frequency, wherein in particular the device is designed to be the second variable as a function of the fourth signal and the first variable to determine.

In further preferred embodiments, it is provided that the second cutoff frequency is greater than the second frequency, preferably greater than three times the second frequency. This ensures that the fourth signal has, in particular, also those signal components which belong to the mentioned mixing products. In addition, the fourth signal also has signal components corresponding to the fundamental frequency.

• a) als Summe der ersten Größe und der zweiten Größe und/oder
• b) in Abhängigkeit des vierten Signals zu ermitteln. Bei weiteren bevorzugten Ausführungsformen charakterisiert die dritte Größe eine von dem Plasma reflektierte Leistung im Bereich der ersten Frequenz (beispielsweise Grundfrequenz) zuzüglich der von dem Plasma reflektierten Leistung wenigstens mancher Mischprodukte.

In further preferred embodiments it is provided that the device is designed to a third size

• a) as the sum of the first size and the second size and / or
• b) depending on the fourth signal to determine. In further preferred embodiments, the third quantity characterizes a power reflected by the plasma in the range of the first frequency (for example fundamental frequency) plus the power of at least some mixed products reflected by the plasma.

In further preferred embodiments, it is provided that the device is designed to determine a fourth variable as a function of the first size and the third size, in particular as a weighted sum of the first size and the third size, wherein the first size is associated with a first weighting factor , and wherein the third size is associated with a second weighting factor. A weighting factor can be a scalar or complex size. With this weighting factor, the size can be multiplied. This can be advantageous, for example, a different load on an output stage of the first high-frequency generator by the respective reflected power components, represented by the first size and the third size, to be taken into account. In further preferred embodiments, the fourth variable can be advantageously used to control a power of the first high-frequency power signal or the first high-frequency generator. For this purpose, the device according to the embodiments can be designed, for example, to transmit the fourth variable to the first high-frequency generator which generates the first high-frequency power signal.

In further preferred embodiments it is provided that the device is designed to determine a fifth size as a function of the first size and the second size, in particular as a weighted sum of the first size and the second size, wherein the first size is associated with a third weighting factor , and wherein the fourth size is associated with a fourth weighting factor. This also advantageously allows, for example, a different load on an output stage of the first high-frequency generator to be taken into account by the respective reflected power components, represented by the first variable and the second variable. In further preferred embodiments, the fifth variable may be advantageously used to control a power of the first high frequency power signal and the first high frequency generator, respectively.

In further preferred embodiments it is provided that the device is designed to determine an, in particular complex-valued, impedance of the plasma, in particular a temporal course of the impedance of the plasma. In further preferred embodiments, the time course of the impedance of the plasma may be e.g. be depicted as a trajectory in a Smith chart.

In other preferred embodiments, a phase measurement may be performed to determine the impedance, e.g. between a voltage wave going to the plasma and a voltage wave returning from the plasma to the first high frequency generator. In further preferred embodiments, to determine the (i.o., complex) impedance with respect to the first frequency or fundamental frequency, e.g. signals derived from said back and forth voltage waves with comparatively narrow band filtering around the fundamental frequency are used. If an optional down conversion takes place, cf. the above remarks on the second signal may e.g. a 2-tuple of signals (a first signal that characterizes the returning voltage wave, analogous to the second signal so, and a second signal that characterizes the corresponding outgoing voltage wave) are obtained by a comparatively strong low-pass filtering (low cut-off frequency) of the respective baseband signal from which the impedance with respect to the fundamental frequency can be determined. Accordingly, in other embodiments, a less heavily filtered signal is to be used for instantaneous complex impedance of the plasma. Applicant's study suggests that, in further preferred embodiments, the impedance, in particular also the instantaneous values of the impedance, can be applied to a position of the trajectory of the impedance in the complex plane, e.g. illustrated in a Smith chart, and that the type of load (e.g., thermal, electrical) of the first high frequency generator is closed by the reflected power.

In other words, in some embodiments, strong filtering may characterize the signals characterizing the back and forth voltage waves and determine the impedance therefrom for the impedance i.w. a point, that is to say a certain value in the complex plane or a corresponding Smith diagram. This value can be used in other embodiments as so-called "matching information" because it characterizes the impedance matching of the first high-frequency generator to the plasma at the fundamental frequency. In further embodiments, a weaker filtering may yield a complete waveform (rather than a point) for the trajectory of impedance. In the case of a filtering which allows only signal components of the sidebands, the determined "impedance" corresponding to this contains exclusively information about effects of the mixture.

In further preferred embodiments, it is provided that the device is designed to additionally determine the fourth variable and / or the fifth variable as a function of the impedance of the plasma, in particular as a function of the time profile of the impedance of the plasma. Thereby, e.g. also a phase of the i.d.R. Complex impedance of the plasma are taken into account. This is particularly useful in those embodiments in which the fourth and / or fifth size is used, for example, for controlling a power of the first high-frequency power signal or of the first high-frequency generator.

In further preferred embodiments, it is provided that the device is designed to output at least one of its operating variables, in particular at least one of the following variables, to an external unit and / or output via a display device: the first variable, the second variable, the third variable, the fourth size, the fifth size. In preferred embodiments, outputting at least one of said quantities to an external unit may, for example, convey the respective quantity or quantities to a high-frequency generator that generates the first high-frequency power signal. For example, an output power of the first high-frequency power signal can be carried out in response to the device-transmitted quantity (s). The visual output of a trajectory of the impedance via a display device is also conceivable in further embodiments.

Further preferred embodiments relate to a method for operating a device for determining an electrical power reflected by a plasma, wherein the plasma can be acted upon by a first high-frequency power signal having a first frequency and at least one second high-frequency power signal having at least one second frequency, wherein the second frequency is smaller than the first frequency, wherein the device determines a first quantity that characterizes a power reflected by the plasma in the range of the first frequency and determines a second quantity that characterizes a power reflected by the plasma in a first frequency range, wherein the first Frequency range has a predetermined number of sum frequencies and / or difference frequencies from the first frequency and an integer multiple of the second frequency.

Further preferred embodiments relate to a high-frequency generator for generating at least one first high-frequency power signal having a first frequency with at least one device according to the embodiments.

In further preferred embodiments, it is provided that the high-frequency generator is designed to regulate the generation of the first high-frequency power signal, in particular by means of a first regulator, as a function of at least two of the following variables: first size, second size, third size, fourth size, fifth size ,

In further preferred embodiments, it may also be provided that the high-frequency generator does not contain the device according to the embodiments, but is configured to receive at least one of the following variables from the device according to the embodiments (for example via a data interface between the device and the high-frequency generator). and to control the generation of the first high-frequency power signal, in particular by means of a first regulator, as a function of at least two of the variables mentioned: first size, second size, third size, fourth size, fifth size.

In further preferred embodiments, it is provided that the high-frequency generator has a first control channel for at least one of the following variables: first size, second size, third size, fourth size, fifth size, and a second control channel for at least one of the following: first Size, second size, third size, fourth size, fifth size. Particularly preferred is e.g. a first control channel for the first size and e.g. a second control channel for the second size provided.

In further preferred embodiments, it is provided that the high-frequency generator is designed to regulate an output power of the first high-frequency power signal in dependence on a time profile of the impedance of the plasma. In preferred embodiments, this corresponds to regulation of the output power as a function of a trajectory of the impedance or the position of the trajectory, for example plotted in a Smith chart. As a result, it can advantageously be achieved that comparatively critical operating states (for example having undesired values for the phase of the impedance) for the high-frequency generator or its output stage with regard to the impedance of the plasma can be reduced or avoided.

In further preferred embodiments it is provided that an impedance transformation (in particular phase rotation) of the impedance of the plasma (or the resulting impedance of the plasma and an optionally present matching network) takes place as a function of the time profile of the relevant impedance. In other words, an impedance transformation, in particular in the sense of a phase rotation, the impedance of the plasma, for example, depending on a position of the trajectory of the impedance in the Smith chart done. As a result, the trajectory of the impedance can be rotated about its origin in the Smith chart so as to lie in relatively less critical regions of the complex plane represented by the Smith chart. For example, regions of different criticality can be defined depending on the topology of an output circuit of the high-frequency generator, and in preferred embodiments, avoiding particularly critical regions, ie undesired values for the time profile or the phase of the impedance, can be achieved by said phase rotation.

The above-mentioned impedance transformation, in particular phase rotation, can in some preferred embodiments, for example, by an adaptation of a line length between the plasma and the optional Adjustment network and the high-frequency generator done. In further preferred embodiments, said impedance transformation, in particular phase rotation, can also take place dynamically, that is to say in particular at a transit time of the high-frequency generator. For this purpose, for example, a corresponding phase shifter device can be provided between the high-frequency generator and the plasma or the optional matching network. Combinations of an adaptation of the line length and a dynamic phase rotation by means of phase shifter means are also conceivable in further preferred embodiments.

Further preferred embodiments relate to a use of a device and / or a method according to the embodiments for transmitting the first size and the second size to a display device and / or to a machine-readable interface for differentiation and / or processing of the two variables.

Further preferred embodiments relate to a use of a device and / or a method according to the embodiments for controlling a high-frequency generator, wherein for the regulation the first variable and the second variable, each with different weighting factors not equal to zero, are included in the regulation.

Further preferred embodiments relate to a use of a device and / or a method according to the embodiments for regulating an impedance matching device, in particular a matching network, wherein for the regulation the first variable and the second variable, each with different weighting factors, are included in the regulation, in particular the first size with a magnitude greater weighting factor than the second size.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the figures of the drawing. All features described or illustrated alone or in any combination form the subject matter of the invention, regardless of their combination in the claims or their dependency and regardless of their formulation or representation in the description or in the drawing.

• 1 schematisch ein vereinfachtes Blockdiagramm einer Vorrichtung gemäß einer Ausführungsform in einem Zielsystem,
• 2A, 2B, 2C jeweils schematisch ein Leistungsdichtespektrum gemäß weiterer Ausführungsformen,
• 3A schematisch ein vereinfachtes Blockdiagramm einer weiteren Ausführungsform,
• 3B schematisch ein vereinfachtes Blockdiagramm einer weiteren Ausführungsform,
• 4 schematisch ein vereinfachtes Blockdiagramm einer weiteren Ausführungsform,
• 5 schematisch ein vereinfachtes Blockdiagramm einer weiteren Ausführungsform,
• 6 schematisch eine Spektraldarstellung von Hochfrequenzleistungssignalen gemäß einer Ausführungsform,
• 7 schematisch eine messtechnisch ermittelte Spektraldarstellung von Hochfrequenzleistungssignalen gemäß einer Ausführungsform,
• 8 schematisch einen zeitlichen Verlauf einer Impedanz eines Plasmas gemäß einer Ausführungsform dargestellt in einem Smith-Diagramm,
• 9 bis 12 jeweils schematisch einen zeitlichen Verlauf einer Impedanz eines Plasmas gemäß einer Ausführungsform dargestellt in einem Smith-Diagramm,
• 13 schematisch ein vereinfachtes Blockdiagramm eines Hochfrequenzgenerators gemäß einer Ausführungsform,
• 14 schematisch ein vereinfachtes Blockdiagramm eines Hochfrequenzgenerators gemäß einer weiteren Ausführungsform,
• 15 schematisch ein vereinfachtes Flussdiagramm eines Verfahrens gemäß einer Ausführungsform,
• 16 schematisch ein vereinfachtes Blockdiagramm einer weiteren Ausführungsform, und
• 17 eine Konfiguration gemäß einer weiteren Ausführungsform.

In the drawing shows:

• 1 2 is a simplified block diagram of a device according to an embodiment in a target system;
• 2A . 2 B . 2C each schematically a power density spectrum according to further embodiments,
• 3A schematically a simplified block diagram of a further embodiment,
• 3B schematically a simplified block diagram of a further embodiment,
• 4 schematically a simplified block diagram of a further embodiment,
• 5 schematically a simplified block diagram of a further embodiment,
• 6 FIG. 2 schematically illustrates a spectral representation of high frequency power signals according to an embodiment; FIG.
• 7 1 schematically shows a metrologically determined spectral representation of high-frequency power signals according to an embodiment,
• 8th FIG. 2 schematically shows a time curve of an impedance of a plasma according to an embodiment, shown in a Smith chart, FIG.
• 9 to 12 each schematically a time course of an impedance of a plasma according to an embodiment shown in a Smith chart,
• 13 2 is a simplified block diagram of a high frequency generator according to an embodiment;
• 14 schematically a simplified block diagram of a high frequency generator according to another embodiment,
• 15 2 is a simplified flowchart of a method according to an embodiment;
• 16 schematically a simplified block diagram of another embodiment, and
• 17 a configuration according to another embodiment.

1 schematically shows a simplified block diagram of a multi-frequency plasma system comprising a plasma chamber PC and a plasma producible therein P , The plasma P For example, for material processing such as for coating or etching of semiconductor devices, etc. can be used. A first high-frequency generator 200 generates a first high frequency power signal having a first frequency, which is also referred to below as a fundamental frequency LS1 , the plasma chamber PC and with that plasma P via a corresponding high-frequency line 210 can be fed. The plasma P accordingly represents for the first high frequency generator 200 an electrical load. One from the first high frequency generator 200 to the plasma P going voltage wave ui that with the first high-frequency power signal LS1 Corresponds is also in 1 shown. It usually contains (especially in a stationary state) only the fundamental frequency.

In preferred embodiments it is provided that the first frequency is between about 10 MHz, megahertz, and about 190 MHz, wherein in particular the first frequency has at least about one of the following values: 13.56 MHz, 27.12 MHz, 40.68 MHz , 60 MHz, 81 MHz, 161 MHz. In other embodiments, other values for the first frequency are possible.

Optionally, between the first high frequency generator 200 and the plasma chamber PC an adaptation network 220 be arranged, which has an impedance matching the impedance of the plasma P preferably such that one of the plasma P in the direction of the first high-frequency generator 200 reflected power at the first frequency or fundamental frequency is reduced. If available, forms the optional customization network 220 together with the plasma P the electrical load for the first high frequency generator 200 , A first line section 210a the high frequency line 210 connects the first high frequency generator 200 with the optional customization network 220 , A second line section 210b Connects the optional customization network 220 with the plasma chamber PC ,

In addition to the first high frequency power signal LS1 is the plasma P in the present case also with a second high-frequency power signal LS2 acted upon by a second high-frequency generator 300 can be generated or provided. The second high frequency power signal LS2 has a second frequency that is less than the first frequency.

In further preferred embodiments, it is provided that the second frequency is between about 10 kHz, kilohertz, and about 2.3 MHz, wherein in particular the second frequency has at least about one of the following values: 300 kHz, 400 kHz, 500 kHz. In other embodiments, other values for the second frequency are possible.

Multi-frequency plasma systems of in 1 shown type are advantageously used in applications where both a high ion density and a high acceleration of the ions is desired, for example, for a material processing as the already mentioned etching.

In the high-frequency excitation of the plasma P, according to preferred embodiments, attention is paid to a good impedance matching, which is characterized by the lowest possible, optimally, no electric power reflected by the load. Thus, on the one hand, for example, the first high-frequency generator 200 in the form of the high frequency power signal LS1 delivered power optimal for excitation of the plasma P exploited and on the other hand stress (especially thermal or electrical type, eg too high temperature and / or voltage) for the first high-frequency generator 200 avoided. For this, in further preferred embodiments, between the first high-frequency generator 200 and the plasma chamber PC the already mentioned optional adaptation network 220 used, for example, can be regulated to obtain an impedance matching with changing process parameters. Alternatively or additionally, for impedance matching in further embodiments, a so-called "frequency tuning" can be performed, that is to say a change in the first frequency of the high-frequency power signal output by the first high-frequency generator LS1 ,

According to investigations by the Applicant, in the multi-frequency plasma system according to FIG 1 among other things by nonlinearities in the plasma P (For example, saturation effects) Mixed products from the introduced into the plasma high frequency power signals LS1 . LS2 , even with an ideal impedance matching or power matching of the first high-frequency generator 200 with respect to the fundamental frequency provided by it for the first high-frequency generator 200 represent a "reflected" performance. Information about the on the plasma P reflected power and thus also over the mixing products are contained, for example, in the returning voltage wave Ur, which differs from the plasma P towards the first high frequency generator 200 spreads.

2A schematically shows a power density spectrum over the frequency axis f According to preferred embodiments, from which the first high-frequency power signal at the first frequency f1 (fundamental frequency) and the second high-frequency power signal emerge at the second frequency f2, wherein the second frequency is smaller than the first frequency f1, cf. also the frequency values or frequency ranges already described above for the first and second frequency. For example, the first frequency f1, ie the fundamental frequency, is about 13.56 MHz, and the second frequency f2 is about 100 kHz. Shown are in 2A in each case those performance shares LS1h . LSH2 that from the first high-frequency generator 200 (Frequency f1) or from the second high frequency generator 300 (Frequency f2) to the plasma P or the plasma chamber PC corresponding voltage waves.

2 B In contrast, schematically shows a power density spectrum for power components of the respective signals, each of the plasma P towards the first high frequency generator 200 returning voltage waves Ur ( 1 ) correspond. Out 2 B it can be seen that with respect to the fundamental frequency f1 there is a mismatch since a power component of a returning voltage wave at the fundamental frequency f1 has a non-zero value. Out 2 B however, it can also be seen that from the plasma P to the first high-frequency generator 200 Mixed products of the fundamental frequency f1 with the second frequency f2 be directed, cf. the sum frequencies fs_1, fs_2, fs_3 and difference frequencies fd_1, fd_2, fd_3 as present in the plasma P by electrical mixing of the two high frequency power signals LS1 . LS2 arise (mixed products).

The sum frequencies can be determined as a function of the equation fs_n = f1 + n * f2, and the difference frequencies can be determined as a function of the equation fd n = f1 -n * f2, where fs_n is an n-th sum frequency, where f1 the first frequency is where n is a natural number greater than zero, where "*" is the multiplication operator, where f2 the second frequency is and where fd_n is an nth difference frequency. Accordingly, in 2 B Sum frequencies and difference frequencies for n = 1, 2, 3 shown.

2C schematically shows a power density spectrum in the case of an optimal adjustment with respect to the fundamental frequency f1 as can be obtained using the principle of the embodiments. Only the power densities of the sum frequencies and difference frequencies, that is to say of the mixed products, which have a first sideband, are clearly visible SB1 and a second sideband SB2 form non-zero amplitude values. These mixed products also provide perfect match with respect to the fundamental frequency f1 one from the plasma P reflected (or generated therein) electrical power that the over the high frequency line 210 with the plasma chamber PC connected first high frequency generator 200 can load. These mixed products or sidebands represent a good excitation of the plasma P So, are not undesirable per se, can be the first high frequency generator 200 however, also load, albeit in a manner other than reflected electrical power at the fundamental frequency f1 , This may be the case in further preferred embodiments, which are described below, for example, with reference to FIG 13 be taken into account, for example, in a regulation of the operation of the first high-frequency generator 200 the reflected electrical power at the fundamental frequency f1 and the reflected electrical power of the mixed products or sidebands according to their actual influence or effect, for example generation of undesired heat losses and / or overvoltages in the first high-frequency generator 200 to be weighted.

In preferred embodiments, cf. this too 1 and 3A , is a device 100 respectively. 100a provided, which is adapted to a first size G1 to determine which one of the plasma P reflected power in the range of the first frequency f1 , ie the fundamental frequency, characterized and a second size G2 to determine which one of the plasma P characterized reflected power in a first frequency range, wherein the first frequency range a predetermined number of sum frequencies fs_1, fs_2, fs_3 ( 2 B) and / or difference frequencies fd_1, fd_2, fd_3 (mixed products) from the first frequency f1 and an integer multiple of the second frequency f2.

The principle according to the embodiments advantageously allows between one of the plasma P reflected power in the range of the first frequency f1, ie fundamental frequency, and a reflected power from the plasma P in the said first frequency range to differentiate. The first frequency range preferably comprises at least part of the mixing products described above, for example the first sideband SB1 and the second sideband SB2 according to 2C , As can be seen, the first frequency range can also comprise a number of subfrequency ranges which are not necessarily directly adjacent to each other, as they are presently provided by the two sidebands SB1 . SB2 are characterized. In particular, the fundamental frequency f1 not included in the first frequency range.

In other words, the first size represents G1 ( 3A) one of the plasma P ( 1 ) reflected power in the range of the fundamental frequency f1 , In particular, excluding the range of also occurring or expected sidebands SB1 . SB2 , and the second size G2 represents one of the plasma P reflected performance of at least part of said mixed products. By determining the first and second size G1 . G2 can be a operation of the plasma P a multi-frequency system are more precisely characterized and evaluated, and optionally also an operation of the high-frequency generator 200 depending on the first and / or second size G1 . G2 be influenced, what with the arrow A2 should be indicated.

For example, in further preferred embodiments for an assessment of Adaptation ("match condition") of the generator impedance of the first high-frequency generator 200 to the load impedance (ie the impedance of the plasma P or the system comprising the plasma P and the optional customization network 220 ) with respect to the fundamental frequency f1 only the reflected fundamental wave are considered, ie the proportion of the reflected power at the fundamental frequency f1 , In other words, in preferred embodiments for assessing the match condition, the first size G1 be evaluated. For example, it is then possible to optimize the impedance or power of the first high-frequency generator 200 to the load impedance with respect to the fundamental frequency f1 be closed when the first size G1 falls below a predetermined first threshold, preferably to zero. At the same time, the second size G2 can be used to stimulate the plasma P to judge.

In preferred embodiments, the device 100 , compare 1 , the first and / or second size G1 . G2 depending on at least one operating variable of the multi-frequency plasma system, which, for example, on the high-frequency line 210 is present and thus can be determined metrologically, compare the block arrow A1 , Particularly preferred is the device 100a ( 3A) designed to be the first size G1 and / or the second size G2 in response to a first signal s1 to determine that one of the plasma P ( 1 ) to the first high frequency generator 200 reflected, ie returning, voltage wave Ur characterized.

4 schematically shows a simplified block diagram of another embodiment. It can be seen that in the present case also the second high-frequency generator 300 an adaptation network 320 assigned. Between the first high-frequency generator 200 and its optional customization network 220 is a directional coupler 230 provided, which is a first signal s1 that provides the plasma P ( 1 ) to the first high frequency generator 200 reflected voltage wave Ur characterizes. Instead of a directional coupler 230 In other embodiments, a voltage / current decoupling ("VI sample", not shown) may be provided and the first signal s1 derived therefrom voltage and current signals are derived.

The first signal s1 is done by means of an input filter 102 a filtering, in particular subjected to low-pass filtering, whereby a filtered signal s1 obtained by means of an analog-to-digital converter (ADC) 104 into a time and value discrete digital signal s1 The input filter is transformed 102 is preferred to the bandwidth of the ADC 104 customized.

The digital signal s1 "is subjected to a down conversion, preferably by mixing, in particular by multiplication, with a local oscillator signal LO , creating a second signal s2 is obtained. The second signal s2 is preferably a (digital) baseband signal (frequency of the local oscillator signal LO essentially corresponds to the fundamental frequency f1 , ie deviations of up to 2%, in particular up to 1%, are tolerable), but in other embodiments may also be an intermediate frequency signal (frequency of the local oscillator signal LO is smaller than the fundamental frequency f1 ).

The device 100 . 100a is further adapted, by means of at least a first low-pass filtering with first cut-off frequency from the second signal s2 a third signal s3 derive. This takes place here by means of the low-pass filters 106 . 108 wherein the first cutoff frequency of the first low pass filtering is less than or about equal to the second frequency f2 is. This can ensure that the third signal s3 has only signal components with the base frequency transformed into the baseband f1 correspond, but not signal components of mixed products. In further embodiments, instead of the two low pass filters 106 . 108 Also, a single low pass filter with the second cutoff frequency can be used to generate the third signal s3 from the second signal s2 to determine. Particularly preferred is the device 100 . 100a designed to be the first size G1 ( 3A) depending on the third signal s3 for example, by forming a square of the magnitude of the third signal s3: G1 = | s3 | ² .

The device 100 . 100a is further configured to derive a fourth signal s4 from the second signal s2 by means of a second low-pass filtering with second cut-off frequency. This takes place here by means of the first low-pass filter 106 wherein the second cut-off frequency of the second low-pass filtering is greater than the second frequency, preferably greater than three times the second frequency. This can ensure that the fourth signal s4 Also has signal components which correspond to the mixing products at least first to third order. In addition, the fourth signal s4 has signal components which correspond to the fundamental frequency f1 transformed into the baseband. In simple terms, it can be stated that the fourth signal s4 contains information about one of the plasma P has reflected power both at the fundamental frequency f1 and in the range of the sum frequencies or difference frequencies of the mixed products, whereas the third signal s3 information about that of the plasma P has reflected power at the fundamental frequency f1, but not in the range of the sum frequencies or difference frequencies of the mixed products.

In preferred embodiments, the functionality is as described above with reference to FIG 4 described components 102 . 104 . LO . 106 . 108 at least partially into the device 100 . 100a integrated.

5 schematically shows a further embodiment. As already described above and out 5 Obviously, the first size becomes G1 that one of the plasma P ( 1 ) reflected power in the range of the first frequency f1 ( 2 B) characterized as the square of the magnitude of the third signal s3 receive.

In a similar way becomes a third size G3 as the square of the amount of the fourth signal s4 optionally, in addition optionally a low-pass filtering by another low pass 109 he follows. This can, especially for a visual display of the third size G3 , be expedient because amplitude values of the fourth signal s4 can be modulated with the second frequency or integer multiples thereof.

Further preferred is the device 100 . 100a designed to be the second size G2 depending on the fourth signal s4 and the first size G1 to determine. How out 5 can be seen, in other preferred embodiments, for example, the second size G2 as the difference from the third size G3 and the first size G1 be determined: G2 = G3 - G1 , The subtraction takes place here by means of an unspecified adder or subtractor.

In further preferred embodiments, those described above with reference to 4 . 5 described steps, for example by means of hardware and / or software or a combination thereof.

In further preferred embodiments, the device 100 . 100a for example, at least iw the in 17 pictured configuration 1000 on.

The configuration 1000 has a computing device 1010 on such as a microcontroller and / or microprocessor and / or digital signal processor (DSP) and / or a programmable logic device (eg FPGA) and / or an application-specific integrated circuit (ASIC) and a memory device 1020 for at least temporary storage of one or more computer programs PRG1 . PRG2 , .... At least one of the computer programs PRG1 . PRG2 can be used to control an operation of the device 100 . 100a , in particular for carrying out the method according to the embodiments, be provided. For example, the determination of at least one of the sizes G1 . G2 . G3 under control of one of the computer programs PRG1 . PRG2 respectively. The storage device 1020 may preferably have a volatile memory 1022 such as a random access memory ("RAM") and / or a non-volatile memory 1024 (eg, read-only memory ("ROM") and / or EEPROM, especially flash EEPROM or the like).

Next, the configuration 1000 a peripheral device 1030 comprising at least one at least partially executed in hardware filter device 1032 (Also analog filter device is possible) and / or mixer device 1034 and / or ADC 1036 and / or data interface 1038 can have. For example, the filter device 1032 in some embodiments, the function of the input filter 102 according to 4 realize. In further embodiments, the ADC 1036 the function of the ADC 104 according to 4 realize. In further embodiments, the mixer device 1034 according to 17 the function of the mixer according to 4 realize, eg a frequency transformation of the signal s1 "into the baseband signal s2 , In further embodiments, the data interface 1038 to output at least one size, for example the first and / or second and / or third size G1 . G2 . G3 to be formed on an external unit (not shown). In the case of the external unit, according to a further embodiment, for example, it may be the first high-frequency generator 200 and / or an external display device.

In further preferred embodiments, the configuration 1000 also an optional display device 1040 have, wherein more preferably a plurality of separate display units 1042 . 1044 . 1046 are provided, for example in the form of liquid crystal (LCD) displays or seven-segment displays or displays of the LED (light emitting diode) - or OLED (organic LED) type. It is preferred on the first display unit 1042 the first size G1 output on the second display unit 1044 the second size G2 , and on the third display unit 1046 the third size G3 ,

In further preferred embodiments, the filter device 1032 according to 17 to realize the function of the input filter 102 according to 4 trained, and the ADC 1036 This can be done at the output of the input filter 102 As already described, the signals s1 'obtained are transformed into the digital domain, that is to say they provide the signal s1 " 4 described processing, in particular the determination of the signals s2, s3, s4, in other preferred embodiments, for example, completely by the computing device 1010 . in particular under the control of a corresponding computer program PRG1 , done as part of a digital signal processing. The lowpass filter 106 . 108 according to 4 can in the configuration 1000 according to 17 for example, by digital FIR (finite impulse response) filters are implemented by the computing device 1010 or corresponding computer programs can be evaluated. In other embodiments, this also applies to the mixture with the local oscillator signal LO ,

In further embodiments is also conceivable, instead of in 4 shown sequence down conversion by mixing with the local oscillator signal LO before analog-to-digital conversion by the ADC 104 perform. This can advantageously be an ADC 104 be provided with a lower bandwidth, for example, again in the form of the ADC 1036 according to the configuration 1000 out 17 , In these embodiments, it may further be provided that the downward conversion by the mixer device 1034 according to 17 is performed.

In further embodiments, it is also conceivable that o.g. Filter steps in the analog domain, so no ADC is required.

In further embodiments, it is also conceivable to determine the second size G2 to use a bandpass filter (not shown) in its filter curve at the fundamental frequency f1 ( 2 B) a notch (English: notch) contains, and whose lower and upper cutoff frequency are chosen so that they cover the first frequency range, thus include the considered mixed products or their sum frequencies and difference frequencies. Alternatively, in further embodiments, the provision of two separate bandpass filters (not shown) for each one of the sidebands SB1 . SB2 conceivable.

In further embodiments, it is also conceivable to have individual filters for each interest sum frequency fs_1, fs_2, .. and / or difference frequency fd_1, fd_2,. 2 B) or for corresponding frequency groups. In further embodiments, it is proposed to provide low-pass filtering after amplification (eg absolute value or squaring) of signals characterizing sidebands, since the amplitude values (power values) of the sidebands may be modulated at the second frequency f2 or multiples thereof.

In further preferred embodiments, the device is 100 . 100a designed to be a fourth size G4 , see. 5 , depending on the first size G1 and the third size G3 to be determined, in particular as a weighted sum of the first size G1 and the third size G3 , where the first size G1 a first weighting factor a is assigned, and wherein the third size G3 a second weighting factor b is assigned. Thus: G4 = a * G1 + b * G3. The fourth size G4 In this case, it characterizes an electric power reflected by the plasma P, wherein a portion of the reflected power in the range of the fundamental frequency f1 is determined by the first quantity G1 and wherein a portion of the reflected power comprising the fundamental frequency f1 and the mixing products by the third magnitude G3 is represented. By appropriate choice of the first and second weighting factors a, b, the respective proportions in a corresponding manner to form the fourth size G4 be weighted. In further preferred embodiments, the fourth size G4 For example, for influencing a generation of the first high-frequency power signal LS1 by the first high-frequency generator 200, compare 1 , be used. For this purpose, the device 100 the fourth size G4 to transmit to the high frequency generator 200, compare the dashed arrow A2 out 1 ,

In further preferred embodiments, the below with reference to 3B are described, the device 100 . 100a designed to be a fifth size G5 depending on the first size G1 and the second size G2 to be determined, in particular as a weighted sum of the first size G1 and the second size G2 , where the first size G1 a third weighting factor c is assigned, and wherein the fourth size G4 a fourth weighting factor d is assigned. Thus: G5 = c * G1 + d * G2. The fifth size G5 In this case, it characterizes an electric power reflected by the plasma P, wherein a portion of the reflected power in the range of the fundamental frequency f1 is determined by the first quantity G1 and wherein a portion of the reflected power comprising the mixing products but not the fundamental frequency f1 is represented by the second quantity G2 is represented. By appropriate selection of the third and fourth weighting factors c, d, the respective proportions can be correspondingly used to form the fifth variable G5 be weighted. In further preferred embodiments, the fifth size G5 for example, for influencing generation of the first high-frequency power signal LS1 by the first high-frequency generator 200 , compare 1 , be used. For this purpose, the device 100 the fifth size G5 to transmit to the high frequency generator 200, compare the dashed arrow A2 out 1 ,

In further preferred embodiments, the device is 100 . 100a adapted to at least one of the following quantities to an external unit 200 spend and / or over an optional display device 110 ( 1 ): the first size G1 , the second size G2 , the third size G3 , the fourth size G4 , the fifth size G5 , The output of one or more of the mentioned sizes G1 , .., G5 can be done, for example, to the first high-frequency generator 200 (see the arrow A2 out 1 ), which in further preferred embodiments, for example, its operation or the generation of the first high-frequency power signal LS1 can influence depending on the output to him variables.

In further preferred embodiments, the device has 100 via a (own) display device 110 for dispensing at least one of said sizes G1 , .., G5 , As a result, the corresponding output variables are visually perceptible, for example by a user of the device 100 or the plasma system. As a result, the user advantageously receives information about an operation of the plasma P , in particular via electrical power reflected by the plasma, wherein advantageously between reflected power in the range of the fundamental frequency f1 (first size G1 ) and reflected power in the area of the mixed products or sidebands (second size G2 ) can be differentiated. 5 indicates this possibility for visual output by the display devices listed by way of example 110a . 110b . 110c on.

6 schematically shows a spectral representation of high frequency power signals according to another embodiment. Shown are power densities of one of the plasma P returning voltage wave Ur ( 1 ) at the fundamental frequency f1 and the second frequency f2 , as well as at in 6 for reasons of clarity unspecified mixed products comprising sum frequencies or difference frequencies from the fundamental frequency f1 and the second frequency f2 around the fundamental frequency f1 around. In further preferred embodiments, filtering (analog or digital) is by means of a first filter curve FC1 suggested to measure the plasma P reflected power in the range of the fundamental frequency f1 and a filtering (analog or digital) using a second filter curve FC2 to give a measure of the power reflected by the plasma P at the fundamental frequency f1 and the mixed products. A measure of the power reflected by the plasma alone in the area of the mixed products (ie without parts of the fundamental frequency f1 ) can be, for example, a difference of the through the filter curves FC1 . FC2 obtained signals are determined. In the above with reference to 6 described embodiments, a transformation into another frequency range such as the baseband range or an intermediate frequency range is not required.

7 schematically shows a metrologically determined spectral representation of one of the plasma P returning voltage wave according to an embodiment over a frequency axis f '. While a power density at the fundamental frequency f1 is relatively small, have proportions of the mixed products from the fundamental frequency f1 and the second frequency f2 corresponding sidebands SB1 ' SB2 'comparatively large power density values.

8th schematically shows a time course of an impedance of the plasma P according to an embodiment, shown as a trajectory T1 in a Smith chart. Unless an optional customization network 220 ( 1 ), corresponds to the trajectory T1 the time course of the resulting impedance of the plasma and the matching network 220 , ie with respect to the first line section 210a in 1 considered to the right. It is off 8th to realize that no complete power adjustment to the impedance of the first high-frequency generator 200 consists. Rather, both phase and magnitude of the impedance vary in time, which is particularly due to the mixing products.

In further preferred embodiments, it can therefore be provided that the device 100 . 100a is designed to have an impedance of the plasma P (or a resulting impedance of the components plasma P and customization network 220 ), in particular the temporal course of the impedance. This may provide information about possibly for the high frequency generator 200 critical operating states can be obtained, which can be characterized by different phase values of the impedance.

Hereinafter, further preferred embodiments will be described in terms of a reduced stress effect by electrical power reflected at the plasma P in the region of the sidebands SB1 . SB2 ( 2C ) on the first high-frequency generator 200 described.

Is the load impedance (eg resulting impedance of the plasma P and the optional matching network 220 ( 1 )) in some embodiments not to the impedance of the first high frequency generator 200 adjusted, there is a partial or complete reflection of the high frequency (RF) power. This is the case, for example, if the load impedance of the "Matchbox 220 plus plasma chamber PC or plasma P " does not correspond to the generator impedance of eg 50 ohms. This can be done, for example, by incorrect setting of the matchbox 220 and / or the fundamental frequency f1 of the high-frequency power signal LS1 output by the high-frequency generator 200 and / or by a change in the Plasmas P happen. In the Smith diagram, this load impedance is represented, for example, by a point which lies outside the center point (= no reflection, load impedance corresponds to generator impedance).

According to investigations by the Applicant, depending on the phase position of the reflected voltage wave Ur ( 1 ) compared to a leading voltage wave Ui ( 1 ), the stress for the first high-frequency generator 200 due to reflected electrical power different effects on different components of the high frequency generator 200 , While at a location of the impedance of the load in certain areas of the Smith chart, components of the first radio frequency generator 200 may be thermal damage, it may be at a position of the impedance in other areas of the Smith chart that a gain element (eg transistor) of the output stage (not shown) destroyed by incorrect switching (eg inductive or capacitive switching) and / or by voltage overshoot becomes. This may also be the case in further embodiments in a 3 dB quadrature coupler generator in which two RF sources are merged in the 3 dB quadrature coupler.

For example, in other embodiments, if the reflected voltage wave Ur does not have the same frequency as the leading fundamental wave Ui, this corresponds to a continuous phase shift. The impedance corresponding to such a reflected voltage wave Ur is not a fixed point in the Smith chart, but a point continuously moving on a circle whose diameter corresponds to the magnitude of the reflected voltage wave Ur and its rotational frequency to a frequency offset of the reflected voltage wave Ur Fundamental wave corresponds. A higher frequency (greater than the fundamental frequency f1, see upper sideband SB2 out 2C ) corresponds to a continuous phase shift to larger angles and thus to a counterclockwise point, a lower frequency (smaller than the fundamental frequency f1, see lower sideband SB2 out 2C ) a clockwise running point. With two mirror-image frequencies (eg first sum frequency fs_1 and first difference frequency fd_1, cf. 2 B) in the lower and upper sidebands, the circles overlap to form a line on which the point in the Smith chart goes back and forth. This is schematically based on the trajectory T2 the impedance according to 9 shown.

If the portions of the returning voltage wave Ur are not the same size with respect to the two frequencies, the line opens to an ellipse, cf. the trajectory T3 out 10 , An additional reflection on the fundamental frequency f1 shifts the center of gravity of the line from the center of the Smith chart, cf. the trajectory T4 out 11 , Spectral components of higher order (eg second sum frequency fs_2 and / or second difference frequency fd_2, cf. 2 B) can bend the line, cf. the trajectory T5 out 12 ,

Since shares of sidebands SB1 . SB2 at the reflected voltage wave Ur no fixed impedance, the first high-frequency generator 200 or its components are not permanently stressed by the reflected electric power in the sidebands, but "only" in time with the various frequency offsets, ie frequency differences between the respective sum frequency or difference frequency and the fundamental frequency f1. Therefore, in other preferred embodiments in the sidebands SB1 . SB2 a higher reflected electric power may be allowed than at the fundamental frequency f1. The determination of the first size G1 and the second size G2 According to the embodiments, in other embodiments advantageously allows a corresponding assessment, as to whether the reflected power associated with the sidebands exceeds a predefinable threshold. For example, in other embodiments, this may be for an employed type of high frequency generator 200 or for whose components are checked, in particular by evaluating a determined during operation of the plasma system second size G2 ,

In further preferred embodiments, provision can be made for certain ranges of values for the impedance of the load not to be assumed, in particular even in the presence of reflected electrical power in the region of the sidebands. In a representation of the time-varying impedance as a trajectory in a Smith chart, this corresponds, for example, to at least one area in the complex impedance plane represented by the Smith diagram, in which the trajectory or parts thereof are not allowed to lie.

Such an impedance region to be avoided is exemplified in FIG 10 with the reference number IG1 designated and hatched for clarity. Although the instantaneous impedance of the plasma P only temporarily within the area IG1 If, compare the above explanations, it may be advantageous in further embodiments, if the trajectory T3 is modified so that at no time the instantaneous impedance of the plasma P in the area IG1 lies.

In further preferred embodiments, this can be achieved by way of example by a phase shift, as for example by changing the electrical length of the high frequency line 210 can be effected. For example, in some embodiments, the length of the radio frequency line may be provided 210 , in particular of the section 210a and / or section 210b change to the desired rotation of the trajectory T3 ( 10 ), in particular with the aim of the trajectory T3 from the area to be avoided IG1 to move out, reach.

In further embodiments, alternatively or additionally, a phase shifter device between the high-frequency generator 200 and the plasma P or the optional matching network 220 be provided. Combinations of an adaptation of the line length and a dynamic phase rotation by means of phase shifter means are also conceivable in further preferred embodiments. Both of the above measures (change in the line length, phase shifter) each cause a phase shift, whereby the iw by the influence of the sidebands SB1 . SB2 resulting trajectory T3 the impedance in the Smith chart can be rotated around the origin.

13 schematically shows a simplified block diagram of a high frequency generator 400 according to a preferred embodiment. The high frequency generator 400 has a, preferably controllable, oscillator 410 (For example, a voltage controlled oscillator, VCO) for generating a high-frequency signal s20 and optionally a driver device 420 , which is preferably formed as a controllable amplifier, and which is adapted to amplify the high-frequency signal s20, whereby an amplified high-frequency signal s21 is obtained. The high frequency generator 400 also has a, preferably also controllable, power amplifier 430 configured to receive the output signal s21 of the driver device 420 continue to amplify, resulting in an output of the power amplifier 430 a high frequency power signal LS1 'is obtained, in preferred embodiments, for example, to excite the plasma P is usable, compare also the first high frequency power signal LS1 according to 1 ,

Optional is a directional coupler 440 provided for the extraction of signals A1 is formed, the information about one of the high-frequency generator 400 outgoing outgoing voltage wave Ui 'and / or one of the plasma P ( 1 ) to the high frequency generator 400 returning voltage wave Ur 'included. The signals A1 'are a device 100b deliverable, which preferably the functionality of the device described above 100 or 100a, thus formed, the first size G1 and the second size G2 to determine. In further preferred embodiments, the device is 100b also designed to at least one of the following sizes G3 . G4 . G5 to determine. Also the device 100b at least in about a configuration 1000 have, as described above with reference to 17 has been described.

In further preferred embodiments, the high frequency generator is 400 configured to generate the high frequency power signal LS1 to be executed or influenced as a function of at least two of the following variables: first size G1 , second size G2 , third size G3 , fourth size G4 , fifth size G5 , in particular by means of a first regulator 402 as a function of at least two of the mentioned variables G1 to G5 to regulate. This may cause operation of the high frequency generator 400 advantageous taking into account both on the plasma P reflected electrical power in the range of the fundamental frequency f1 as well as from the plasma P reflected electric power in the area of the sidebands SB1 . SB2 be executed or influenced. In particular, an ideal impedance or power adjustment with respect to the fundamental frequency f1 can thereby be carried out in a particularly advantageous manner, so that, accordingly, that of the plasma P reflected electric power at the fundamental frequency f1 becomes zero.

In further preferred embodiments, the high frequency generator 400 a first control channel R1 for at least one of the following sizes: first size G1 , second size G2 , third size G3 , fourth size G4 , fifth size G5 , and a second control channel R2 for at least one other of the following sizes: first size G1 , second size G2 , third size G3 , fourth size G4 , fifth size G5 , An optional third control channel is also conceivable and in 13 through the arrow R3 indicated. In other words, in further preferred embodiments, at least one, preferably also several of the sizes G1 , .., G5 for influencing at least one component 410 . 420 . 430 of the high-frequency generator 400 be used.

In further preferred embodiments, for a regulation of the high-frequency generator 400 depending on the plasma P or the load reflected electrical power, the shares of the fundamental frequency f1 and the sidebands SB1 . SB2 be weighted differently on the total reflected electrical power. Do the sidebands SB1 . SB2 For example, only half the stress effect as the fundamental frequency f1 on the high frequency generator 400 , Prpsideband = Prfundamental + 0.5 * must be used for the scheme, Pr for example, the fifth size G5 For example, Prfundamental is the first size G1 For example, Prsideband is the second size G2 corresponds, s. also the description too 3B , In the present case, therefore, the third weighting factor c is the value 1 and the fourth weighting factor d is 0.5. Other values for the weighting factors are also conceivable in further preferred embodiments and can also be dependent, for example, on circuit components of the high-frequency generator 400 , eg, a transistor (not shown) of the power amplifier 430 , are selected, for example, depending on the dielectric strength of the transistor, etc.

14 schematically shows a simplified block diagram of a high frequency generator 400a according to another embodiment. For example, the high frequency generator 400a may be coupled to the high frequency generator 400 as shown in FIG 13 have comparable structure and be designed to output a high frequency power signal LS1 " 14 is apparent to the high frequency generator 400a a phase shifter 404 which causes a predetermined phase shift of the high-frequency power signal LS1 ", whereby the phase-shifted high-frequency power signal LS1 '''is obtained, for example, the plasma P ( 1 ) can be fed. The phase shifter device 404 may be used alternatively or in addition to a change in the line length of a high-frequency line carrying the high-frequency power signal LS1 "in order to influence a trajectory of the impedance, see also the above with reference to 10 made statements.

15 schematically shows a simplified flowchart of a method according to an embodiment. In a first step 500 determines the device 100 ( 1 ) a first size G1 ( 3A) which is one of the plasma P ( 1 ) reflected power in the range of the first frequency f1 characterized. In step 502 determines the device 100 a second size G2 which characterizes a power reflected by the plasma P in the first frequency range, the first frequency range comprising the above-described predefinable number of sum frequencies fs_1, fs_2, fs_3 and / or difference frequencies fd_1, fd_2, fd_3 ( 2 B) from the first frequency f1 and an integer multiple of the second frequency f2. In some embodiments, the steps 500 . 502 also be executed in a different order and / or at least partially overlapping in time.

In an optional step 510 determines the device 100 the third size G3 a) as the sum of the first size G1 and the second size G2 and / or b) in response to the fourth signal s4 , s. 4 , Optionally, in step 510 also other sizes from the already determined sizes G1 . G2 . G3 be determined or derived, such as the fourth size G4 ( 5 ) and / or the fifth size G5 ( 3B) , and / or other quantities derivable thereof.

In another, optional step 520 gives the device 100 at least one of the sizes G1 to G5 to an external unit, eg the first high-frequency generator 200 , out. Alternatively or additionally, the device 100 at least one of the sizes G1 to G5 via a display device 110 ( 1 ) so that it is visually perceptible by a person. This advantageously allows control of the operation of the plasma system or of the first high-frequency generator 200.

16 schematically shows a simplified block diagram of a further embodiment, in addition to the above with reference to 4 described configuration, a consideration of the to the plasma P going voltage wave Ui occurs. This is done by means of the directional coupler 230 provided a signal s10 that is to the plasma P going voltage wave Ui characterized.

The signal s10 is detected by means of another input filter 101 a filtering, in particular low-pass filtering, whereby a low-pass filtered signal s10 'obtained by means of an analog-to-digital converter (ADC) is obtained. 103 is transformed into a time- and value-discrete digital signal s10 " 101 is preferred to the bandwidth of the ADC 103 customized.

The digital signal s10 "is subjected to a downward conversion, preferably by mixing, in particular by means of multiplication, with the local oscillator signal LO , whereby a further signal s12 is obtained. The signal s12 is preferably a (digital) baseband signal (frequency of the local oscillator signal LO iw corresponds to the fundamental frequency f1 ), but in other embodiments may also be an intermediate frequency signal (frequency of the local oscillator signal LO is smaller than the fundamental frequency f1 ).

With knowledge of the complex-valued baseband signals s2, s12, the (usually) complex impedance of the load (plasma P or combination of plasma P and optional matching network 220 ( 1 )) be determined.

In further preferred embodiments, the device is 100 . 100a . 100b designed to be the fourth size G4 and / or the fifth size G5 additionally determined as a function of the impedance of the load. In particular, for example, in determining the fourth size G4 and / or the fifth size G5 used weighting factors a, b, c, d possibly depending on the impedance of the load, for example, as a function of a time average of the impedance or a phase, preferably taking into account the position of the trajectory in the Smith chart formed or changed.

The principle according to the embodiments enables an improved power adjustment with respect to the fundamental frequency, in particular in the case of multi-frequency plasma systems, as well as a precise characterization of an excitation of the plasma P , Furthermore, the principle according to the embodiments enables a load of the first high-frequency generator 200 due to reflected power in the area of the sidebands SB1 . SB2 to be determined precisely and possibly reduced.

Further preferred embodiments relate to a use of a device and / or a method according to the embodiments for the transmission of the first size G1 and the second size G2 to a display device and / or to a machine-readable interface for distinguishable presentation and / or processing of the two variables G1 . G2 ,

Further preferred embodiments relate to a use of a device and / or a method according to the embodiments for controlling a high-frequency generator 200 . 400 . 400a , where for the scheme the first size G1 and the second size G2 be included in the scheme with different weighting factors not equal to zero.

Further preferred embodiments relate to a use of a device and / or a method according to the embodiments for controlling an impedance matching device, in particular a matching network 220 , where for the scheme the first size G1 and the second size G2 each with different weighting factors are included in the scheme, in particular the first size G1 with a magnitude greater weighting factor than the second size G2 ,

Claims (22)

Device (100; 100a; 100b) for determining an electrical power reflected from a plasma (P), the plasma (P) having a first high-frequency power signal (LS1) having a first frequency (f1) and at least one at least one second frequency (f2 ), wherein the second frequency (f2) is less than the first frequency (f1), wherein the device (100; 100a; 100b) is designed to determine a first variable (G1) ( 500) characterizing a power reflected by the plasma (P) in the range of the first frequency (f1) and determining (502) a second quantity (G2) characterizing a power reflected by the plasma (P) in a first frequency range , wherein the first frequency range has a predefinable number of sum frequencies (fs_1, fs_2, fs_3) and / or difference frequencies (fd_1, fd_2, fd_3) from the first frequency (f1) and an integer multiple of the second frequency equenz (f2). Device (100; 100a; 100b) according to Claim 1 , wherein the sum frequencies (fs_1, fs_2, fs_3) can be determined as a function of the equation fs_n = f1 + n * f2, and / or wherein the difference frequencies (fd_1, fd_2, fd_3) can be determined as a function of the equation fd_n = f1-n * f2 where fs_n is an n-th sum frequency, where f1 is the first frequency (f1), where n is a natural number greater than zero, where "*" is the multiplication operator, where f2 is the second frequency (f2), and where fd_n is an n-th difference frequency. The apparatus (100; 100a; 100b) of at least one of the preceding claims, wherein the first frequency (f1) is between about 10 MHz, megahertz, and about 190 MHz. The apparatus (100; 100a; 100b) of at least one of the preceding claims, wherein the second frequency (f2) is between about 10 kHz, kilohertz, and about 2.3 MHz. Device (100; 100a; 100b) according to at least one of the preceding claims, wherein the device (100; 100a; 100b) is designed to have the first variable (G1) and / or the second variable (G2) in dependence on a first signal (s1) which characterizes a voltage wave (Ur) reflected from the plasma (P) to a first high-frequency power generator (200; 400) providing the first high-frequency power signal (LS1). Device (100; 100a; 100b) according to Claim 5 wherein the device (100; 100a; 100b) is adapted to transform the first signal (s1) or a signal (s1 ', s1 ") derived therefrom by a down conversion into a second signal (s2), wherein in particular the second one Signal (s2) is a baseband signal. Device (100; 100a; 100b) according to Claim 6 wherein the device (100; 100a; 100b) is adapted to mix the first signal (s1) or a signal derived therefrom (s1 ', s1 ") with a local oscillator signal (LO) to supply the second signal (s2) receive. Device (100; 100a; 100b) according to at least one of Claims 6 to 7 wherein the device (100; 100a; 100b) is designed to derive a third signal (s3) from the second signal (s2) by means of at least one first low-pass filtering with first cut-off frequency, in particular the device (100; 100a; 100b) is designed to determine the first variable (G1) as a function of the third signal (s3). Device (100; 100a; 100b) according to Claim 8 wherein the first cutoff frequency is less than or equal to the second frequency (f2), preferably less than the second frequency (f2). Device (100; 100a; 100b) according to at least one of Claims 6 to 9 wherein the device (100; 100a; 100b) is designed to derive a fourth signal (s4) from the second signal (s2) by means of a second low-pass filtering with a second cutoff frequency, wherein in particular the device (100; 100a; 100b) is designed for this purpose is to determine the second quantity (G2) as a function of the fourth signal (s4) and the first quantity (G1). Device (100; 100a; 100b) according to at least one of the preceding claims, wherein the device (100; 100a; 100b) is designed to generate a third variable (G3) a) as the sum of the first variable (G1) and the second variable (G) G2) and / or b) as a function of the fourth signal (s4) (510). Device (100; 100a; 100b) according to Claim 11 wherein the device (100; 100a; 100b) is adapted to determine a fourth quantity (G4) as a function of the first size (G1) and the third size (G3), in particular as a weighted sum of the first size (G1) and the third quantity (G3), wherein the first quantity (G1) is associated with a first weighting factor (a), and wherein the third quantity (G3) is associated with a second weighting factor (b). Device (100; 100a; 100b) according to at least one of the preceding claims, wherein the device (100; 100a; 100b) is designed to determine an impedance of the plasma (P), in particular a time profile of the impedance of the plasma (P) , Device (100; 100a; 100b) according to Claim 13 and 12 wherein the device (100; 100a; 100b) is designed to additionally determine the fourth variable (G4) and / or a fifth variable (G5) as a function of the impedance of the plasma (P). Apparatus (100; 100a; 100b) according to at least one of the preceding claims, wherein the apparatus (100; 100a; 100b) is adapted to output (520) and (520) at least one of the following quantities to an external unit (200; 400; 400a) or output (520) via a display device (110; 1040): the first size (G1), the second size (G2), the third size (G3), the fourth size (G4), a fifth size ( G5). Method for operating a device (100; 100a; 100b) for determining an electrical power reflected from a plasma (P), the plasma (P) having a first high-frequency power signal (LS1) having a first frequency (f1) and at least one at least one second frequency (f2) having a second frequency (f2), the second frequency (f2) being smaller than the first frequency (f1), the device (100; 100a; 100b) determining a first quantity (G1) (500 ) which characterizes a power reflected by the plasma (P) in the range of the first frequency (f1) and determines (502) a second quantity (G2) which characterizes a power reflected by the plasma (P) in a first frequency range, the first frequency range a predefinable number of sum frequencies (fs_1, fs_2, fs_3) and / or difference frequencies (fd_1, fd_2, fd_3) from the first frequency (f1) and an integer multiple of the second Frequency (f2) has. A high frequency generator (200; 400; 400a) for generating at least one first high frequency power signal (LS1) having a first frequency (f1) with at least one device (100; 100a; 100b) according to at least one of Claims 1 to 15 , High frequency generator (200; 400; 400a) after Claim 17 wherein the high-frequency generator (200; 400; 400a) is configured to regulate the generation of the first high-frequency power signal (LS1) by means of a first regulator (402) as a function of at least two of the following variables: first variable (G1), second variable (G2 ), third size (G3), fourth size (G4), fifth size (G5). High frequency generator (200; 400; 400a) after Claim 18 wherein the high frequency generator (200; 400; 400a) has a first control channel for at least one of the following quantities: first magnitude (G1), second magnitude (G2), third magnitude (G3), fourth magnitude (G4), fifth magnitude (G5 ), and a second control channel for at least one other of the following sizes: first size (G1), second size (G2), third size (G3), fourth size (G4), fifth size (G5). Use of a device (100; 100a; 100b) for at least one of Claims 1 to 15 and / or a method according to Claim 16 for transmitting the first size (G1) and the second size (G2) to a display device and / or to a machine-readable interface for distinguishable presentation and / or processing of the two variables (G1, G2). Use of a device (100; 100a; 100b) for at least one of Claims 1 to 15 and / or a method according to at least one of Claims 16 . 20 for controlling a high-frequency generator (200; 400; 400a), wherein for the control the first variable (G1) and the second variable (G2), each with different weighting factors not equal to zero, are included in the control. Use of a device (100; 100a; 100b) for at least one of Claims 1 to 15 and / or a method according to at least one of Claims 16 . 20 to 21 for regulating an impedance-matching device, in particular a matching network (220), the first variable (G1) and the second variable (G2), each having different weighting factors, being included in the control for regulation, in particular the first variable (G1) having a larger magnitude Weighting factor as the second size (G2).

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