Plasma ignition detection device for connection to an impedance matching circuit of a plasma generation system

Abstract

The plasma ignition detection device (1), which is connected to an impedance matching circuit (50) of a plasma generation system (100), is configured to a) process a first time-varying measurement value from a first predetermined location of the impedance matching circuit (50), where from the first time-varying measurement value a first applied reactive and / or active power can be determined, b) process a second time-varying value associated with a second location of the impedance matching circuit (50), where the second location is different from the first predetermined location and from the second value a second applied reactive and / or active power can be determined, c) determine a first time-varying amount from the first measurement value, d) determine a second time-varying amount from the second value, and e) generate an output signal representative of a plasma state in dependence on the first and second time-varying amounts.

Description

[Technical field]

[0001] The present invention relates to a plasma ignition detection device for connection to an impedance matching circuit of a plasma generation device, and to a plasma generation system including such a plasma ignition detection device. [Background technology]

[0002] Surface treatment of workpieces using plasma and gas lasers is an industrial process in which plasma is generated, particularly in a plasma chamber, using direct current or high-frequency alternating current signals with operating frequencies in the range of several tens of kHz to GHz.

[0003] The plasma chamber is connected to a high frequency generator (HF generator) via further electronic components such as coils, capacitors, wires, transformers, etc. These further components can be resonant circuits, filters, or impedance matching circuits.

[0004] During plasma processing, the electrical load impedance of the plasma chamber (plasma = consumer) generated during the process often varies greatly depending on the conditions inside the plasma chamber, especially the characteristics of the workpiece, electrodes, and gas conditions.

[0005] High frequency generators have a limited operating range, which is related to the impedance of the electrical load (= consumer) to which they are connected. If the load impedance exceeds the permissible range, the HF generator may be damaged or destroyed.

[0006] For this purpose, an impedance matching circuit (matchbox) is usually required to transform the impedance of the load to the nominal impedance of the generator output (often 50 ohms). In the case of a mismatch, not all of the generator output can be delivered to the load. Instead, part of the power is reflected. Within the range of the nominal impedance, there is an impedance range within which the generator operates stably and is not damaged, i.e. the transformed load impedance range. If the transformed load impedance is outside this nominal impedance range, the generator can be damaged by the reflected power and become unstable.

[0007] Various impedance matching circuits are known. Impedance matching circuits consist of electrical components, in particular coils and capacitors, which are fixedly set and have a given transformation effect and therefore do not change during operation. This is particularly useful for constant operations such as gas lasers. Furthermore, impedance matching circuits are also known in which at least some of the components of the impedance matching circuit are mechanically variable. For example, motor-driven variable capacitors are known, whose capacitance value is variable by changing the arrangement of the capacitor plates relative to each other.

[0008] Schematically, three impedance ranges can be assigned to the plasma: Before ignition, a very high impedance is present; In normal operation, i.e. in the case of the intended operation of the plasma, a lower impedance is present; In the case of undesired local discharges (arcs) or plasma fluctuations, a very low impedance can occur. In addition to these three specified impedance ranges, further special situations can occur, which are assigned other impedance values. If the load impedance changes suddenly, in which case the load impedance or the transformed load impedance falls outside the permitted impedance range, the HF generator or the transmission device between the HF generator and the plasma chamber can be damaged. There are also undesired stable states of the plasma.

[0009] An impedance matching circuit is described in, for example, Patent Document 1.

[0010] However, determining whether the plasma has ignited or not can be difficult. If the plasma does not ignite when the HF generator is switched on, the resulting "no ignition" impedance may be within the matching range of the impedance matching circuit (matchbox). The impedance matching circuit matches this impedance (essentially by its own losses). For HF generators, matching is nevertheless necessary. This situation occurs by chance and is difficult to detect. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] German Patent Application Publication No. 102009001355A1 Summary of the Invention [Problem to be solved by the invention]

[0012] It is therefore an object of the present invention to provide a plasma ignition detection device and a plasma generation system equipped with such a plasma ignition detection device, which allows for a more accurate indication of the plasma (ignited, not ignited, etc.) and allows for setting a desired plasma state. [Means for solving the problem]

[0013] This problem is solved with respect to a plasma ignition detection device according to claim 1 and with respect to a plasma generation system according to claim 27. Advantageous further embodiments of the plasma ignition detection device are defined in claims 2 to 26 and advantageous further embodiments of the plasma generation system are defined in claims 28 to 31.

[0014] The plasma ignition detection device according to the invention is used for connection to an impedance matching circuit of a plasma generation system. The plasma ignition detection device is configured to process a first time-varying measurement value (hereinafter referred to as "time-varying measurement value"). The first time-varying measurement value represents a physical quantity present at a first predefined location of the impedance matching circuit. For example, the first predefined location may be an input. From the first time-varying measurement value, a first reactive and / or active power to be applied can be determined. By the term "time-varying" it is understood that the measurement value may change over time. The plasma ignition detection device is further configured to process a second time-varying value. The second time-varying value represents a physical quantity present at a second predefined location of the impedance matching circuit. For example, the second predefined location may be an output. The first and second predefined locations are separate, i.e. spaced apart, from each other. This means that other elements (for example capacitors, coils, etc.) are arranged between the two locations. From the second time-varying value, a second reactive and / or active power to be applied can be determined. The plasma ignition detection device is further configured to determine a first time-varying quantity (hereinafter referred to as "time variable") from the first measured value. The plasma ignition detection device is also configured to determine a second time variable from the second value. The plasma ignition detection device is further configured to generate an output signal, preferably representative of the plasma state, depending on the first and second time variables. The term "depending on" is understood to mean that both the first time variable and the second time variable are taken into account. The term "representing" can, for example, mean an indication of whether the plasma has ignited as desired (for example completely ignited). It can thus also mean an indication that a plasma process is in progress, that the plasma has ignited partially, that a plasma process is not possible or that the plasma has not ignited.It can also be used to draw conclusions about the state of the plasma, and thus a presentation indicating that a certain process is complete (e.g., that an etching process is complete) is conceivable. From the change in the output signal over time, a changing plasma can also be inferred, whereby this change in time represents the plasma, whereby the change in the output signal depends inter alia on the state of the plasma.

[0015] It is particularly advantageous that time-varying measured values ​​and values ​​are detected from which the respective reactive and / or active powers can be determined, and that these measured values ​​or values ​​are processed to generate corresponding time-varying quantities therefrom. By being able to determine the reactive and / or active powers, there is a precise phase relationship between the individual quantities, preferably with an accuracy of less than 3°, less than 1°, less than 0.5° or less than 0.2°, so that the relationship between the individual measured quantities or values ​​can be shown more precisely than in the prior art. Due to this additional information, the plasma ignition detection device according to the invention makes it possible to obtain much more precise information about the current plasma state than was previously possible.

[0016] The output signal is preferably a control command for controlling an impedance matching circuit, whereby the HF generator of the plasma generation system is matched. Complementarily or alternatively, the output signal can also be a control command for the HF generator of the plasma generation system, so that the HF generator can be switched on / off and / or its frequency and / or power can be changed. The control command is then primarily used to set the desired plasma state. Complementarily or alternatively, the output signal is an output message, for example displayed on a screen and / or passed to a higher-level control device, so that the operator of the plasma generation system can be informed about the desired and / or undesired states of the plasma in the plasma chamber.

[0017] As a further development, the plasma ignition detection device comprises a memory device, which is preferably a non-volatile memory. The memory device may include various a) a first and a second time variation; and / or b) first and second reactive powers and / or active powers, and / or c) a ratio of the first and second reactive powers and / or active powers; The control commands for the impedance matching circuit and / or the HF generator for the plasma ignition detection device are stored. This can be done, for example, in the scope of a look-up table. a) the current first and second time variations, and / or b) the first and second current reactive and / or active powers, and / or c) a ratio of the first and second current reactive and / or active powers; based on which corresponding control commands for the impedance matching circuit and / or the HF generator are loaded from the memory device and transmitted to the impedance matching circuit and / or the HF generator.

[0018] The term "current" is understood to mean that the plasma ignition detection device always generates new or current time variations from current time variation measurements or values ​​during operation. Since the plasma is not constant, these time variation measurements or values ​​change. In this way, appropriate control commands can be generated very efficiently.

[0019] In the case of forming a ratio between different powers, the efficiency can be determined independently of the absolute input or output power, which favors the operating conditions not only in a specific value range, but in a wide value range.

[0020] In a further development, the plasma ignition detection device includes an AI module, which preferably comprises: a) based on the first and second time variations; and / or b) based on the first and second reactive and / or active powers; and / or c) based on a ratio of the first and second reactive and / or active powers; It is trained by the manufacturer to generate control commands for the impedance matching circuit and / or the HF generator. Actual measurements from an existing plasma generation system can be considered as the basis of training data. In this case, "supervised learning" can be used. Also the use of "unsupervised learning" is conceivable.

[0021] In a further development, the plasma ignition detection device comprises: a) linking the first time variation and the second time variation to one another via at least one mathematical operation; and / or b) linking the first reactive power and / or the active power and the second reactive power and / or the active power to each other via at least one mathematical operation; The impedance matching circuit is adapted to generate an output signal depending on the result. By determining the first and second time variations or the first and second reactive and / or active powers for two different points, it is possible to very efficiently determine what state the plasma is currently in. If significantly more active power (preferably 15% or more, 25% or more, 50% or more, 100% or more, 200% or more, 300% or more, 400% or more, 500% or more, or 600% or more) is transferred to the impedance matching circuit than the power supplied to the plasma, it can be assumed that the plasma is not in the desired state.

[0022] In a further development, the plasma ignition detection device is configured to divide the second reactive and / or active power by the first reactive and / or active power to calculate the efficiency and generate an output signal depending on the efficiency. Long-term studies have confirmed that the efficiency, which requires precise knowledge of the phase relationship (e.g. between current and voltage) for its determination, is a very good criterion for representing the plasma state. A low efficiency means that the plasma is in an unfavorable state.

[0023] In a further development, the plasma ignition detection device comprises: a) the first time variation and / or the first reactive power and / or the first active power exceed a threshold value; and / or b) configured to generate an output signal only if the second time variation and / or the second reactive power and / or active power exceeds a threshold value. It has therefore been determined that the control of the impedance matching circuit and / or the HF generator must be performed at a certain or higher efficiency. Until the generation of the output signal, the HF generator is activated and / or the impedance matching circuit is transferred to a basic or starting state. Too early control of the HF generator and / or the impedance matching circuit based on the output signal can cause difficulties and a stable state may not be achieved. Preferably, the output signal is only output when the efficiency exceeds a level of 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or a level of 45% or more. Until then, preferably, a start-up program, already known, is processed.

[0024] In a further development, the first time-varying quantity is reactive or active power. Complementarily or alternatively, the second time-varying quantity is reactive or active power. What is common to both quantities is that for their calculation, a precise phase relationship for the time-varying measured values ​​or for the time-varying values ​​at the first and second locations must be known. This allows the plasma state to be determined very accurately.

[0025] In a further development, the plasma ignition detection device detects a second reactive power and / or a second active power, a) the first harmonic, or b) configured to calculate the first and second harmonics.

[0026] The plasma ignition detection device further includes: a) the first harmonic, or b) is configured to generate an output signal depending on the power of the first and second harmonics. It is recognized that the stable state of the plasma may also result in undesired states. Such states can be detected, for example, by analysis of harmonics. Preferably, only the first harmonic or the first and second harmonics are detected at a second location, which is arranged at the output of the impedance matching circuit or is arranged closer to the output of the impedance matching circuit than the first location. Furthermore, if the first harmonic or the first and second harmonics of the second reactive and / or active power are determined, the efficiency can be calculated more accurately. Harmonics are also called "harmonics" and are generated by the nonlinearity of the plasma. The impedance matching circuit acts as a filter for these harmonics. Thus, most of these harmonics can be better measured at the output of the impedance matching circuit. For the first reactive and / or active power, this is not absolutely necessary. This is because preferably the first reactive power and / or active power is measured at the input of the impedance matching circuit, thereby being measured close to the HF generator, and the HF generator supplies only the fundamental wave.

[0027] In a further development, the first location is in the region of the HF input of the impedance matching circuit and the second location is in the region of the HF output of the impedance matching circuit. Alternatively, the reverse is also possible. In this case, the first location is in the region of the HF output of the impedance matching circuit and the second location is in the region of the HF input of the impedance matching circuit. In this case, the first and second harmonics can be determined at the first location. In this case, in particular since the two locations are as far away from each other as possible, this basically allows the most accurate values ​​of the first and second time quantities to be determined.

[0028] In a further development, a first measuring unit is provided, the first measuring unit being configured to determine a first time-varying measured value at a first predetermined point of the impedance matching circuit, the determination being effected by physical measurement.Furthermore, a second measuring unit is provided, the second measuring unit being configured to determine a second time-varying value, the second measuring unit being configured to determine a second time-varying value at a first predetermined point of the impedance matching circuit, the determination being effected by physical measurement. a) the determination is made by a physical measurement at a second location, such that the second time-varying value is also a time-varying measurement; or b) The determination is of the impedance matching circuit, and I) of the first time-varying measurement, and / or II) The first time change amount is calculated based on a physical model. In this case, the first measurement unit is a real measurement unit. The second measurement unit can be a real or virtual measurement unit depending on the embodiment. If the second measurement unit is a virtual measurement unit, the first time-varying measured value or the first time-varying quantity can be used as input quantity. Furthermore, the current settings of the impedance matching circuit (e.g. the current values ​​of the adjustable capacitance and / or inductance) can also be used. From these quantities, the second time-varying value and therefrom the second time-varying quantity can be determined. In so doing, parasitic elements, in particular ohmic losses of the components, can also be taken into account. This allows the efficiency calculation to be more accurate.

[0029] In a further development, the first and / or the second measuring unit comprises a directional coupler. By means of such a directional coupler, the reactive power and / or the active power can be determined in a simple manner. In an alternative and / or supplementary further development, the first and / or the second measuring unit comprises a voltage-current detector, in particular with a phase detector for determining the phase between the voltage and the current. By means of such a detector, the reactive power and / or the active power can be determined in a particularly simple manner.

[0030] In a further development, the first time-varying measurement is the power of the incoming and outgoing waves (of the first measurement unit) and the second time-varying measurement is the power of the outgoing and incoming waves (of the second measurement unit). The plasma ignition detection device is configured to subtract the power of the outgoing wave from the power of the incoming wave, thereby calculating the first time-varying amount. Furthermore, the plasma ignition detection device is configured to subtract the power of the incoming wave from the power of the outgoing wave, thereby calculating the second time-varying amount.

[0031] In a further development, the first measuring unit comprises a current sensor and a voltage sensor (instead of a directional coupler). In this case, the first time-varying measurement value comprises the current and the voltage, in particular the phase between this current and this voltage. Complementarily or alternatively, the second measuring unit comprises a current sensor and a voltage sensor (instead of a directional coupler). In this case, the second time-varying measurement value comprises the current and the voltage, and optionally also the phase. Basically, the first measuring unit can comprise a current sensor and a voltage sensor, whereas the second measuring unit can comprise a directional coupler. Vice versa is also conceivable. However, preferably, both the first measuring unit and the second measuring unit comprise appropriate current and voltage sensors. The use of such sensors allows very accurate measurements.

[0032] In a further development, the first time-varying measurements are complex currents and complex voltages. Complementarily or alternatively, the second time-varying measurements are complex currents and complex voltages. What is important here is that the phase relationship between current and voltage can be accurately determined, which can be used to calculate reactive and / or active power. This allows a very accurate indication of the efficiency, i.e. how much of the power delivered by the HF generator is actually received by the plasma, and thus ultimately of the plasma state.

[0033] In a further development, the plasma ignition detection device is configured to calculate a first active power from the first time-varying measurement value as follows: |U| |I| cos(φ U -φ I ), or |U| |I| cos(φ I -φ U ) Here, φ U = voltage phase, and φ I = current phase. And / or The plasma ignition detection apparatus is configured to calculate a second active power from the second time varying measurement as follows: |U| |I| cos(φ U -φ I ), or |U| |I| cos(φ I -φ U ) Here, φ U = voltage phase, and φ I = current phase.

[0034] Additionally or alternatively, the plasma ignition detection apparatus is configured to calculate a first reactive power from the first time varying measurement as follows: |U| |I| sin(φ U -φ I ), or |U| |I| sin(φ I -φ U ) Here, φ U = voltage phase, φ I = current phase. And / or The plasma ignition detection apparatus is configured to calculate a second reactive power from the second time varying measurement as follows: |U| |I| sin(φ U -φ I ), or |U| |I| sin(φ I -φ U ) Here, φ U = voltage phase, φ I = current phase.

[0035] It will be appreciated that the more accurately the phase is determined, the more accurately the respective active or reactive power can be calculated.

[0036] In a further development, the plasma ignition detection device comprises a first and a second A / D converter and a first and a second I / Q demodulator. The first A / D converter is configured to digitize a first time-varying measurement value for the current, where the first I / Q demodulator is connected to an output of the first A / D converter. The second A / D converter is configured to digitize a first time-varying measurement value for the voltage, where the second I / Q demodulator is connected to an output of the second A / D converter. Complementarily or alternatively, the plasma ignition detection device comprises a third and a fourth A / D converter and a third and a fourth I / Q demodulator. The third A / D converter is configured to digitize a second time-varying measurement value for the current, where the third I / Q demodulator is connected to an output of the third A / D converter. A fourth A / D converter is formed to digitize the second time-varying measurement value for the voltage, and a fourth I / Q demodulator is connected to the output of the fourth A / D converter. Each A / D converter can be integrated together with the respective I / Q demodulator in one common case or in one common chip. Also, several A / D converters can be integrated on one chip or in one case. Several A / D converters can in particular be operated synchronously. In this way, the phase relationship can be determined very accurately.

[0037] Alternatively or additionally, the I / Q demodulation can be performed in time division multiplexing. This can be done by switching channels. Not all quantities can be measured simultaneously, but they can be measured at different times. If the channels are configured identically, quantities can be reused.

[0038] In a further development, the plasma ignition detection device is configured to set the clock rates of the third and fourth A / D converters as follows: a) the fundamental of an HF generator and a second harmonic of the HF generator, where the second harmonic of the HF generator is mirrored to the Nyquist frequency of the third and fourth A / D converters, or b) a fundamental of the HF generator, a second harmonic of the HF generator, and a third harmonic of the HF generator, where the second and third harmonics of the HF generator are mirrored to the Nyquist frequencies of the third and fourth A / D converters; Separated by a predetermined frequency range below the Nyquist frequency, or by a maximum frequency range.

[0039] Alternatively or additionally, the fundamental can be placed in the second Nyquist zone and the harmonic oscillations in a different zone. This very efficient procedure makes it possible to digitize signals with frequencies of 25 MHz and above, for example, using an A / D converter operating at a clock of 50 MHz. For example, if the fundamental (first harmonic) is 13.56 MHz, this can be digitized without any problems. The second harmonic (first harmonic) has a frequency of 27.12 MHz. This frequency is above 25 MHz. However, a part of this signal is mirrored at the Nyquist frequency (=25 MHz) and is at 22.88 MHz (25 MHz-(27.12 MHz-25 MHz)) and can be digitized. The third harmonic (second harmonic) has a frequency of 40.68 MHz. This is above 25 MHz. However, part of this signal is mirrored at the Nyquist frequency (=25MHz) and is at 9.32MHz (25MHz-(40.68MHz-25MHz)). In summary, this means that the fundamental is at 13.56MHz, the first harmonic mirrored at the Nyquist frequency is at 22.88MHz, and the second harmonic mirrored at the Nyquist frequency is at 9.32MHz. By choosing the appropriate clock rate for each A / D converter, the Nyquist frequency can be chosen as far away as possible so that the above signals can be detected by the use of appropriate filters. Thereby, no expensive A / D converters are required.

[0040] In a further development, the plasma ignition detection device is configured to set the frequency of the local oscillators of the first and second I / Q demodulators and / or the third and fourth I / Q demodulators to the frequency of the HF generator.

[0041] In a further development, the plasma ignition detection device comprises: a) a fifth and a sixth I / Q demodulator, or b) a fifth, sixth, seventh, and eighth I / Q demodulator.

[0042] The output of the third A / D converter is a) to a fifth I / Q demodulator, or b) connected to the fifth and seventh I / Q demodulators.

[0043] The output of the fourth A / D converter is a) to a sixth I / Q demodulator, or b) connected to the sixth and eighth I / Q demodulators.

[0044] The plasma ignition detection device is a) setting the frequency of the local oscillators of the fifth and sixth I / Q demodulators to twice the frequency of the HF generator, or b) the frequency of the local oscillators of the fifth and sixth I / Q demodulators is set to twice the frequency of the HF generator, and the frequency of the local oscillators of the seventh and eighth I / Q demodulators is set to three times the frequency of the HF generator.

[0045] This makes it possible to properly detect the first harmonic, or the first and second harmonics, of the current and voltage.

[0046] In a further development, the plasma ignition detection device includes a signal conditioning device, the I / Q output of each I / Q demodulator being connected to the signal conditioning device, the signal conditioning device being configured to perform one or more of the following operations: a) signal filtering; b) Downsampling, c) Error correction.

[0047] Downsampling here means in particular downclocking, i.e. the deliberate reduction of the clock and the associated reduction in data.

[0048] By error correction is meant here, for example, the correction of amplitude / phase errors and crosstalk. Furthermore, the signal conditioning device is designed to generate complex voltage and current values. It is particularly advantageous here if the signal conditioning device outputs complex voltage and current values, respectively, so that the appropriate phase angles are available.

[0049] In a further development, the voltage sensor of the first measuring unit is a capacitive voltage divider, whereby a first capacitance is formed by a conductive ring or cylinder, through which the HF wiring is wired between the HF generator and the impedance matching circuit. The current sensor of the first measuring unit is a coil arranged around the conductive ring or cylinder. Complementarily or alternatively, the voltage sensor of the second measuring unit is a capacitive voltage divider, whereby a first capacitance is formed by a conductive ring or cylinder, through which the HF wiring is wired between the impedance matching circuit and the consumer (in the plasma chamber). The current sensor of the second measuring unit is a coil arranged around the conductive ring or cylinder.

[0050] In a further development, exactly one side of the voltage sensor of the first and / or second measuring unit formed as a conductive ring or cylinder is grounded. Additionally or alternatively, the coil of the current sensor of the first and / or second measuring unit is a Rogowski coil. This allows particularly accurate measurement values ​​to be obtained.

[0051] In a further development, the first time variation is a peak value or an average value over the determined plurality of first time variations. Complementarily or alternatively, the second time variation is a peak value or an average value over the determined plurality of second time variations, whereby the obtained time variation measurements are smoothed.

[0052] In a further development, the plasma ignition detection device is configured to continuously calculate new values ​​for the first and second time variables using new first time-varying measurements and new second time-varying values, and the actual output signal is then continuously generated depending on these new values ​​for the first and second time variables, the calculation being performed at least once, at least 10 times, at least 100 times, at least 1000 times, at least 10000 times, or at least 100000 times per second.

[0053] In a further development, the plasma ignition detection device is configured to average a plurality of first and / or second time change measurements, to calculate a first time change from the averaged first time change measurements, and to calculate a second time change from the averaged second time change. Complementarily or alternatively, the plasma ignition detection device is also configured to average a plurality of values ​​of the first time change and to average a plurality of values ​​of the second time change and to generate an output signal depending on the result. This "averaging" is preferably performed over a longer period, for example over a period of 5 samples or more, in particular over a period of 10 samples or more. This is because adjusting the capacitance (for example via a variable capacitor) always takes a certain amount of time. Instantaneous adjustment is usually not possible. So that ignition can be recognized, for example, before the motor starts to change the capacitance. Or even while the motor is running, in order to recognize at which impedance / motor position ignition has taken place. So that, for example, this position can be defined as a new starting position for the next process start.

[0054] A plasma generation system according to the present invention comprises a plasma ignition detection device, the system further comprising an impedance matching circuit, wherein the first predetermined location is in the region of an HF input of the impedance matching circuit and the second location is in the region of an HF output of the impedance matching circuit.

[0055] In a further development, the plasma generation system comprises at least one HF generator and at least one consumer in the form of a plasma chamber. In particular, the HF generator can be connected to an HF input of an impedance matching circuit. The line length between the HF generator and the HF input of the impedance matching circuit can be at least 2, 3, 4, 5, 6, 7 or at least 8 times longer than the line length between the HF output of the impedance matching circuit and the at least one consumer.

[0056] In a further development, the plasma generation system includes a display device, preferably in the form of a screen. The plasma ignition detection device is configured to display an output signal on the display device. In particular, an output representative of the plasma state is visualized. The display device can also be a lamp system, whereby, for example, a green lamp visualizes a desired plasma state and a red lamp visualizes an undesired plasma state.

[0057] In a further development, the plasma ignition detection device is configured to output an output signal to the HF generator and / or to the impedance matching circuit and / or to a higher-level control system in which the desired plasma state was previously created, if the desired plasma state does not exist. In this case, a number of output signals in which the desired plasma state was set can be stored. These output signals can then be loaded and transmitted to the HF generator and / or to the impedance matching circuit and / or to the higher-level control system, thereby increasing the probability of setting the desired plasma state.

[0058] In a further development, the plasma generation system includes an optical device disposed within the plasma chamber and configured to detect the plasma condition. The plasma ignition detection device is also configured to generate an output signal dependent on the detected plasma condition. This provides a further control example that can detect the current state of the plasma. Such a device can also be advantageously used for training by providing feedback regarding the state of the plasma, e.g., "good", "bad", "ignited", "not ignited", etc.

[0059] In a further development, a statistical evaluation can be provided. This can be done, for example, by clustering. After a certain number of runs of the process, for example 3, 4 or 5 states can be recognized that occur particularly frequently. Of these, state 1 can be "not ignited" and state 2 can be "ignited". Additional states can also be recognized. The additional states can be, for example, several different "good" and / or "ignited" states for different process steps. Additionally or alternatively, further "bad" and / or "not ignited" and / or "poor ignition, insufficient plasma formation" states can also be recognized. It can be output which of these states is present during the run of the process. The assignment to one of these states can be determined in the form of a probability, output and can be transmitted, for example, to a higher-level control system.

[0060] The higher-level control system can be connected to a cloud-based storage device or a cloud-based data processing device. Cloud-based here means in particular a remote, preferably anonymized, storage device or data processing device in which user ratings from one or more, preferably tens, hundreds or thousands of different users are stored. This allows different users to contribute to the optimization of the process, independent of the production location. It is recognized that the method described above can only achieve great results, i.e. classification information with the correct classification, with the highest probability, if tens of thousands, in particular hundreds of thousands of user ratings are read out. Such an amount of data is often achievable within a given period of time for one production facility.

[0061] Various embodiments of the invention will now be described, by way of example only, with reference to the drawings in which like objects are provided with like reference symbols and in which corresponding figures show details. [Brief description of the drawings]

[0062] [Figure 1] FIG. 1 illustrates an embodiment of a plasma generation system including an HF generator, an impedance matching circuit, a plasma ignition detection device, and a plasma chamber. [Figure 2A] FIG. 2 is a diagram illustrating an embodiment of an impedance matching circuit. [Figure 2B] FIG. 13 is a diagram showing another embodiment of an impedance matching circuit. [Figure 2C] FIG. 13 is a diagram showing another embodiment of an impedance matching circuit. [Diagram 3] FIG. 2 shows an embodiment of a first and / or second measuring unit for contactlessly measuring voltage and current. [Figure 4] FIG. 2 shows another side of the first and / or second measuring unit. [Figure 5A] FIG. 1 illustrates one embodiment for digitizing voltage and current and resolving the phase relationship between voltage and current. [Figure 5B]FIG. 1 illustrates another embodiment for digitizing voltage and current and resolving the phase relationship between voltage and current. [Figure 6] 1 is a graph showing that high efficiency can be recognized as an indication of desirable plasma conditions. [Figure 7] 1 is a graph illustrating that low efficiency can be recognized as a symptom of undesirable plasma conditions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0063] FIG. 1 shows a plasma generation system 100 that is particularly useful for treating the surface of a workpiece.

[0064] The plasma generation system 100 comprises a plasma ignition detection device 1, an impedance matching circuit 50, an HF generator 60 and a plasma chamber 70 (consumer). The HF generator 60 is electrically connected to the impedance matching circuit 50. This connection is made via a first wire 2a, preferably a first coaxial cable 2a. The first wire 2a is connected to an output 60a of the HF generator 60 and to an input 50a of the impedance matching circuit 50. The impedance matching circuit 50 is further electrically connected to the plasma chamber 70. This connection is made via a second wire 2b, preferably a second coaxial piece. The second wire 2b is connected to an output 50b of the impedance matching circuit 50 and to an input of the plasma chamber 70. Preferably, the second wire 2b is connected to an electrode in the plasma chamber 70. The second wire 2b is usually very short and is usually coaxial, but not formed as a cable.

[0065] The first wire 2a is longer than the second wire 2b, preferably 2, 3, 4, 5, 6, 7 or at least 8 times longer than the second wire 2b.

[0066] The plasma generation system 100 includes a display device 80, which is preferably a screen.

[0067] The plasma chamber 70 can be regarded as a consumer. Depending on the application, for example, one or more electrodes 3 can be provided in the plasma chamber 70, at least one of which is connected to the second wiring 2b. In FIG. 1, the plasma 4 is shown as a dot inside the plasma chamber 70.

[0068] Preferably, the plasma generation system 100 also includes an optical device 90. The optical device 90 is further preferably disposed within the plasma chamber 70 and configured to visually detect the plasma 4 and thus the plasma conditions. The optical device 90 may be, for example, a light guide such as an optical fiber. Cameras may also be used, but are often not used for cost reasons. Lenses and other protective glass may quickly become fogged by the plasma 4.

[0069] In the following, the plasma ignition detection device 1 and the impedance matching circuit 50 will be particularly described.

[0070] The plasma ignition detection device 1 comprises a first measuring unit 5 and a second measuring unit 6. The first measuring unit 5 is configured to determine a first time-varying measured value at a first predetermined location of the impedance matching circuit 50, the determination being performed by physical measurement. The first predetermined location is in particular an input 50a of the impedance matching circuit 50.

[0071] The second measuring unit 6 is formed to determine a second time-varying value. This determination is performed at a second predefined location. The second time-varying value can be a second time-varying measured value. This is the case when the determination is also performed by physical measurement. Alternatively, the determination can also be performed by calculation on the basis of a physical model of the impedance matching circuit 50. The physical model includes current quantities of the impedance matching circuit 50. To this belong in particular current values ​​of adjustable or settable components, such as capacitors, for example in the form of variable capacitors, and of resistance components, including in particular parasitic resistance components. In the calculation, the first time-varying measured value of the first measuring unit 5 or quantities derived therefrom are also included. The second predefined location is in particular the output 50b of the impedance matching circuit 50.

[0072] The measuring units 5, 6 which measure real quantities are also called real measuring units 5, 6. The measuring units 5, 6 which determine the corresponding values ​​by calculation based on a physical model are also called virtual measuring units 5, 6.

[0073] The plasma ignition detection device 1 includes a processing unit 7, which is preferably a processor (e.g. a digital signal processor (DSP) or a microcontroller) and / or an FPGA (field programmable gate array). Communication with the first and second measurement units 5, 6 in the plasma ignition detection device 1 is performed via the processing unit 7. Also via the processing unit 7, the plasma ignition detection device 1 can communicate with an HF generator 60, an impedance matching circuit 50, a display device 80, a higher level control system 81 and / or an optical device 90.

[0074] The plasma ignition detection device 1 is configured to process a first time-varying measured value, which can be determined, for example, at a first location by a first measuring unit 5. With the aid of this first time-varying measured value, a first reactive power and / or active power must be determinable. The plasma ignition detection device 1 is further configured to process a second time-varying value, which can be determined, for example, at a second location by a second measuring unit 6. With the aid of this second time-varying value, a second reactive power and / or active power must be determinable.

[0075] Furthermore, the plasma ignition detection device 1 must be configured to determine a first time variation from the first measured value and a second time variation from the second value.

[0076] Finally, the plasma ignition detection device 1 should be configured to generate an output signal indicative of the plasma state of the plasma 4 in the plasma chamber 70 in dependence on the first and second time quantities.

[0077] The output signal may be, for example, a control command for controlling the impedance matching circuit 50. The control command may specify how to change the value of an adjustable or settable component, such as a capacitor, for example in the form of a variable capacitor. For example, the control command may include information that capacitor 1 should be increased in terms of its capacitance, capacitor 2 should be decreased in terms of its capacitance, or should take on a certain value.

[0078] Complementarily or alternatively, the output signal may include a control command for controlling the HF generator 60. Thus, the control command may indicate that the HF generator 60 should be turned off. Complementarily or alternatively, the control command may instruct the HF generator 60 to change its frequency and / or its output power.

[0079] Additionally or alternatively, the output signal may include an output message displayed by display device 80 .

[0080] The plasma ignition detection device 1 preferably includes a memory device 8. The memory device 8 may be part of the processing unit 7 or may be separate from the processing unit 7, in which case the memory device 8 is configured to exchange data with the processing unit 7. In the memory device 8, control commands for the impedance matching circuit 50 and / or the HF generator 60 for various first and second time quantities and / or the first and second reactive powers and / or active powers and / or the ratio of the first and second reactive powers and / or active powers are stored. The plasma ignition detection device 1 is then configured to load from the memory device 8 and transmit to the impedance matching circuit 50 and / or the HF generator 60 corresponding control commands for the impedance matching circuit 50 and / or the HF generator 60 based on the current first and second time quantities and / or based on the current first and second reactive powers and / or based on the current ratio of the first and second reactive powers and / or active powers. This allows the plasma generation system 100 to be rapidly brought to a desired (operating) state, in particular by means of a further data processing device designed to carry out the above steps. The formation of the above ratio between different powers allows the efficiency to be determined independent of the absolute input or output power. Due to the formation of the ratio, this works advantageously not only in a specific operating state, but also in a wide range of operating states.

[0081] Basically, it is also conceivable that the plasma ignition detection device 1 comprises an AI module 9. The AI ​​module 9 may be part of the processing unit 7 or may be separate from the processing unit 7. The AI ​​module 9 is preferably arranged to exchange data with the processing unit 7. The AI ​​module 9 is preferably trained by the manufacturer to generate control commands for the impedance matching circuit 50 and / or the HF generator 60 based on the first and second time quantities and / or based on the first and second reactive and / or active powers and / or based on the ratio of the first and second reactive and / or active powers. The plasma ignition detection device 1 is then arranged to transmit the generated control commands to the impedance matching circuit 50 and / or the HF generator 60.

[0082] The AI ​​module 9 preferably comprises a number of input nodes. These are part of the input layer. The input nodes may be supplied with a first time-varying measurement determined at a first predefined location by a first measurement unit 5. Complementarily or alternatively, the first time-varying quantity may also be supplied to the input nodes. Preferably, the input nodes are also supplied with a second time-varying value determined at a second predefined location by a second measurement unit 6. Complementarily or alternatively, the second time-varying quantity may also be supplied to the input nodes. The first time-varying measurement may be a current and a voltage or a power of the waves entering and leaving the first location. The second time-varying value may be a current and a voltage or a power of the waves entering and leaving the second location. Essentially, the input nodes may also be supplied with values ​​of the power entering the first location and values ​​of the power leaving the second location. As described above, a statistical evaluation may be performed in this embodiment. This may be done, for example, by clustering as described above.

[0083] The AI ​​module 9 preferably comprises one or more output nodes, which are part of the output layer. Such output nodes indicate, for example, how the value of a capacitor in the form of an adjustable or configurable component, for example a variable capacitor, needs to be changed. In the simplest case, node 1 is mapped to capacitor 1 and node 2 to capacitor 2. Depending on the value of the node, a certain capacitance needs to be set or the capacitance needs to be increased or decreased. Thus, one node can be provided for each adjustable element in the impedance matching circuit 50. Basically, one or more further nodes can be provided, whose values ​​adjust the HF generator 60 (switch on, switch off, increase or decrease frequency, increase or decrease power). There can also be nodes indicating whether the plasma 4 is in the desired state. From this, an output signal in the form of an output message for the display device 80 can be generated.

[0084] The AI ​​module 9 preferably includes one or more hidden layers connected to the output nodes via the input nodes. Each hidden layer may include the same number of nodes. The number of nodes in each hidden layer may also differ from each other. Basically, it is considered that each node in the input layer is connected to each node in the first hidden layer (the hidden layer located closest to the input layer). However, basically, there may be nodes in the input layer that are not connected to the nodes in the first hidden layer.

[0085] Essentially, the AI ​​module 9 can be trained using "supervised learning" based on the acquired data. To that end, as described above, the optical device 90 can provide feedback on the state of the plasma. Thus, the first time-varying measurement value and the second time-varying value from the existing installation of the plasma generation system 100 together with the adjusted and verified plasma state and / or the generated control commands for the HF generator 60 and / or the impedance matching circuit 50 can be used to properly train the AI ​​module 9. Thereby, it is possible to monitor whether the AI ​​module 9 generates the correct output signal in the form of a control command for controlling the impedance matching circuit 50 or for controlling the HF generator 60 for a given first time-varying measurement value and a second time-varying value.

[0086] The plasma ignition detection device 1 is in particular formed in such a way that the first time-varying quantity and the second time-varying quantity are linked to one another via at least one mathematical operation. Additionally or alternatively, the first reactive power and / or the active power and the second reactive power and / or the active power can be linked to one another via at least one mathematical operation, and an output signal can be generated depending on the respective result.

[0087] The plasma ignition detection device 1 is preferably configured to divide the second reactive and / or active power by the first reactive and / or active power (possible mathematical operation) in order to calculate the efficiency. An output signal is then generated depending on the efficiency. It is assumed here that the second reactive and / or active power is determined near or at the output 50b of the impedance matching circuit 50 and the first reactive and / or active power is determined near or at the input 50a of the impedance matching circuit 50. In the opposite case, the first reactive and / or active power would have to be divided by the second reactive and / or active power.

[0088] Furthermore, preferably, the plasma ignition detection device 1 is configured to generate an output signal only if the first time variation and / or the first reactive and / or active power exceed a threshold value. Additionally or alternatively, this also applies if the second time variation and / or the second reactive and / or active power exceed a threshold value. At start-up of the plasma generation system 100, there may be cases in which a premature comparison of the first reactive and / or active power with the second reactive and / or active power may cause insufficient control.

[0089] Preferably, the first time-varying quantity is a reactive power or an active power, and more preferably, the second time-varying quantity is a reactive power or an active power. The reactive power or active power at the first and / or second location is fed to the AI ​​module 9 at an input node.

[0090] As mentioned above, the first location can be located in the region of the HF input 50a of the impedance matching circuit 50 and the second location can be located in the region of the HF output 50b of the impedance matching circuit 50, or vice versa.

[0091] 2A and 2B show different embodiments of the impedance matching circuit 50. In Fig. 2A, the impedance matching circuit 50 is L-shaped. In Fig. 2B, the impedance matching circuit 50 is T-shaped.

[0092] In FIG. 2A, the input 50a of the impedance matching circuit 50 is connected to the first coil 10 (first inductance) and the second coil 11 (second inductance). The first and second coils 10, 11 have their first connections connected to a common node and are thereby connected to the input 50a of the impedance matching circuit 50. The first coil 10 is connected to a reference ground via a first capacitor 12 (first capacitance). The second coil 11 is connected to the output 50b via a second capacitor 13 (second capacitance). The first and second capacitors 12, 13 are adjustable components, particularly in the form of variable capacitors, whose capacitances can be changed via stepping motors. In particular, the plate spacing of the first and second capacitors 12, 13 can be changed. The plasma ignition detection device 1 is formed to appropriately control the respective stepping motors. Alternatively or additionally, electronically variable capacitances, for example capacitor arrays that can be turned on and off, can be used for setting the capacitance values. Basically, the processing unit 7 can perform the control. The capacitances of the first and second capacitors 12, 13 can be adjusted independently of each other. Preferably, the impedance matching circuit 50 does not include further components. Of course, the positions of the first coil 10 and the first capacitor 12 can also be swapped. In this case, the first capacitor 12 is arranged at the input 50a of the impedance matching circuit 50 and the first coil 10 is arranged at the reference ground. Complementarily or alternatively, the positions of the second coil 11 and the second capacitor 13 can also be swapped. In this case, the second capacitor 13 is arranged at the input 50a of the impedance matching circuit 50 and the second coil 11 is arranged at the output 50b.

[0093] The input 50a of the impedance matching circuit 50 is connected in FIG. 2B to the first capacitor 12 (first capacitance). The first capacitor 12 is connected to both the first coil 10 (first inductance) and the second coil 11 (second inductance). This is done via a common node to which the first capacitor 12 and both the first and second coils 10, 11 are connected. The first coil 10 is further connected to a reference ground. The second coil 11 is connected (series connection) to a second capacitor 13 (second capacitance). The second capacitor 13 is connected to the output 50b of the impedance matching circuit 50. It is also possible to reverse the positions of the second coil 11 and the second capacitor 13. In this case, the second capacitor 13 is connected to the common node and the second coil 11 is connected to the output 50b of the impedance matching circuit 50. Preferably, the impedance matching circuit 50 does not include any further components.

[0094] Basically, each impedance matching circuit 50 can be represented as a series of two-port (two-terminal pair) circuits 501-505. A two-port circuit is a model of an electrical component or network with four connection ends, each of which together forms a so-called port. A port exists if the current through both connections of a port is the same, i.e. if the port conditions are fulfilled. A two-port circuit is a special form of a general four-port. In each two-port circuit, at most one variable component is arranged, but it is not necessary that one variable component is arranged in each two-port circuit. Such an example is shown in FIG. 2C. In this case, the first two-port circuit 501 is a post-matching section without a variable element. The following two-port circuit 502 has a first variable element, for example the first capacitor 12 of FIG. 2A or FIG. 2B. The following two-port circuit 503 is an intermediate matching section without a variable element. The further following two-port circuit 504 has a second variable element, for example the second capacitor 13 of FIG. 2A or FIG. 2B. The following two-port circuit 505 is a pre-matching section without variable elements. It is not necessary that all two-port circuits are present. Several can be combined into one.

[0095] 3 shows an embodiment of a possible construction of the first and / or second measuring unit 5, 6. In this embodiment, the first and / or second measuring unit 5, 6 is configured to measure voltages and currents contactlessly.

[0096] For this purpose, the first or second measuring unit 5, 6 comprises a current sensor 15 and a voltage sensor 16. The first and second time-varying measurements are therefore current and voltage.

[0097] Preferably, of course, the phase relationship is also measured. Therefore, the first and second time-varying measurements are complex currents and complex voltages. In the case of measurements using directional couplers, at least one real power measurement is obtained without a phase measurement. This is a major advantage of directional couplers. However, for impedances far removed from the characteristic impedance of the directional coupler, the limited directivity reduces the accuracy.

[0098] The current sensor 15 of the first and / or second measuring unit 5, 6 is in the form of a coil, in particular a Rogowski coil.

[0099] The two ends of the coil are preferably connected together via a shunt resistor 17. The voltage dropped across the shunt resistor 17 can be digitized using a first A / D converter 18.

[0100] The voltage sensor 16 of the first and / or second measuring unit 5, 6 is preferably formed as a capacitive voltage divider. A first capacitance 19 is formed by a conductive ring 19. A conductive cylinder can also be used. The corresponding first or second wiring 2a, 2b is routed through this conductive ring 19. A second capacitance 20 of the voltage sensor 16 formed as a voltage divider is connected to the reference ground. A second A / D converter 21 is connected in parallel to the second capacitance 20 and is formed to detect and digitize the voltage dropped by the second capacitance 20.

[0101] Basically, the first measuring unit 5 and the second measuring unit 6 can also be arranged or formed on a (common) circuit board. The first capacitance 19 can be formed by coating layers on a first side and an opposing second side of the circuit board. In this case, the coating layers on the first and second sides are electrically connected to each other by vias. The first or second wiring 2a, 2b is fed through an opening in the circuit board. The second capacitance 20 can be formed by discrete components.

[0102] The current sensor 15 in the form of a coil, in particular a Rogowski coil, is further away from the first or second wiring 2a, 2b than the first capacitance 19. The coil, together with the vias, can also be formed on the same circuit board by suitable coating layers. The coil for measuring the current and the first capacitance for measuring the voltage preferably run through a common plane.

[0103] The shunt resistor 17 may also be placed on this circuit board, as may the first and / or second A / D converters 18, 21.

[0104] FIG. 4 shows another aspect of FIG. 3 in the form of a partial cross-section, in particular through the first or second wiring 2a, 2b, the first capacitance 19 and the current sensor 15 in the form of a coil, in particular in the form of a Rogowski coil. It can be seen that the coil is bent around the ring-shaped first capacitance 19. The coil is then galvanically isolated from the first capacitance 19. The coil comprises a spiral winding (preferably collar-insulated) and is located around the outer casing of the ring-shaped first capacitance 19. The second end of this winding is guided through the accommodation space widened by the winding and thereby emerges at the first end of the winding. The coil is preferably wound around the ring-shaped first capacitance 19 by more than 270°.

[0105] Basically, it is conceivable that one side of the part of the voltage sensor 16 of the first and / or second measuring unit 5, 6 formed as an electrically conductive ring 19 or cylinder (first capacitance) is just grounded. Preferably, the second side is electrically connected to the second capacitance 20.

[0106] In another embodiment (not shown), the first and / or second measurement unit 5, 6 may comprise a directional coupler.

[0107] In this case, the first time-varying measurement (taken at a first location) is the power of the incoming and outgoing waves (at the first location) and the second time-varying measurement (taken at a second location) is the power of the outgoing and incoming waves (at the second location). The plasma ignition detection device 1 is configured to subtract the power of the outgoing wave from the power of the incoming wave, thereby calculating the first amount of change over time. Furthermore, the plasma ignition detection device 1 is configured to subtract the power of the incoming wave from the power of the outgoing wave, thereby calculating the second amount of change over time.

[0108] As mentioned at the beginning, it is also possible to use a hybrid structure, so that the first measuring unit 5 comprises a current sensor 15 and a voltage sensor 16 and the second measuring unit 6 comprises a directional coupler, or vice versa.

[0109] As mentioned at the beginning, one of the two measurement units 5, 6 can also be a virtual measurement unit, whereby the time change measurement value, or the time change amount calculated therefrom, is not measured but calculated based on a physical model of the impedance matching circuit 50 and the time change measurement value of the other (actual) measurement unit 5, 6, or the time change amount calculated therefrom.

[0110] FIG. 5A shows an embodiment for digitizing the current and voltage time-varying measurements and ascertaining the phase relationship between the current and the voltage. The time-varying measurements of the current (analog current signal) causing a voltage drop across the shunt resistor 17 or the voltage (analog voltage signal) dropped across the second capacitance 20 of the voltage sensor 16 formed as a voltage divider are preferably filtered using a first filter 22, respectively. In this case, the first filter 22 is a band-pass filter. There is such a first filter 22 for filtering the voltage time-varying measurements and there is also such a filter 22 for filtering the current time-varying measurements. Other types of filters (e.g. low-pass filters) are also conceivable. The filtered current signal is subsequently digitized by the first A / D converter 18. The filtered voltage signal is likewise digitized by the second A / D converter 21.

[0111] The digitized current time change measurement value output by the first A / D converter 18 is supplied to a first I / Q demodulator 23, which outputs an I / Q signal corresponding to the digitized current time change measurement value. The digitized voltage time change measurement value output by the second A / D converter 21 is supplied to a second I / Q demodulator 24, which outputs an I / Q signal corresponding to the digitized voltage time change measurement value. The first A / D converter 18 and the first I / Q demodulator 23 can be integrated on a common chip. The same can be done for the second A / D converter 21 and the second I / Q demodulator 24.

[0112] The frequency of the first and second I / Q demodulators 23 , 24 is preferably set to the frequency of the HF generator 60 .

[0113] The plasma ignition detection apparatus 1 further includes a signal conditioning device 25. The outputs of the first and second I / Q demodulators 23, 24 are connected to the signal conditioning device 25. The signal conditioning device 25 is configured to perform one or more of the following operations: signal filtering, downsampling, and error correction. The signal conditioning device 25 is additionally configured to generate complex voltage and current values.

[0114] The structures shown in Fig. 5A may be part of the respective first or second measurement unit 5, 6. Preferably, they are part of the first measurement unit 5, which detects the current and voltage at a first point (the input 50a of the impedance matching circuit 50). The signal conditioning device 25 may be formed by the processing unit 7. The signal conditioning device 25 may also be arranged separately from the processing unit 7. The first and second I / Q demodulators 23, 24 may also be part of the signal conditioning device 25 or the processing unit 7.

[0115] Based on the magnitudes of the currents and voltages and their respective phases, the plasma ignition detection device 1 is arranged to calculate a first active power from the (in this case) first time-varying measurement value as follows: |U|·|I|·cos(φ U -φ I ), or |U| |I| cos(φ I -φ U ), where φ U = voltage phase, and φ I = current phase. In principle, the plasma ignition detection device 1 can also calculate the first reactive power from this first time-varying measurement as follows: |U|·|I|·sin(φ U -φ I ), or |U| |I| sin(φ I -φ U ), where φ U = voltage phase, φ I = current phase. In this case, the active power or reactive power is the first time-varying quantity.

[0116] The plasma ignition detection device 1 is configured to continually calculate new values ​​for the first time variation quantity using new first time variation measurements.

[0117] 5B shows a further embodiment for digitizing the current and voltage time-varying measurements and resolving the phase relationship between the current and voltage. This embodiment shows how a second time-varying measurement is detected. This second time-varying measurement is preferably the current and voltage determined at a second location (the output 50b of the impedance matching circuit 50).

[0118] The time-varying measurements of the current causing a voltage drop across the shunt resistor 17 (analog current signal) or the voltage drop across the second capacitance 20 of the voltage sensor 16 formed as a voltage divider (analog voltage signal) are preferably filtered, respectively, via a second filter 26. In this case, the second filter 26 is a band-pass filter. Other types of filters (e.g. low-pass filters) are also conceivable. The filtered current signal is subsequently digitized by a third A / D converter 27. The filtered voltage signal is likewise digitized by a fourth A / D converter 28.

[0119] The digitized current time-varying measurement value output by the third A / D converter 27 is supplied to a third I / Q demodulator 29, which outputs an I / Q signal corresponding to the digitized current time-varying measurement value. The digitized voltage time-varying measurement value output by the fourth A / D converter 28 is supplied to a fourth I / Q demodulator 30, which outputs an I / Q signal corresponding to the digitized voltage time-varying measurement value. The third A / D converter 27 and the third I / Q demodulator 29 can be integrated on a common chip. The same can be done for the fourth A / D converter 28 and the fourth I / Q demodulator 30.

[0120] The frequency of the third and fourth I / Q demodulators 29 , 30 is preferably set to the frequency of the HF generator 60 .

[0121] The outputs of the third and fourth I / Q demodulators 29, 30 are connected to a signal conditioning device 25. The signal conditioning device 25 is configured to perform one or more of the following operations: signal filtering, downsampling, and error correction. The signal conditioning device 25 is also configured to generate complex values ​​of voltage and current, which are second time-varying measurements.

[0122] The plasma ignition detection device 1 is configured to calculate a second active power based on the magnitudes of the current and voltage and the respective phases of the current and voltage from the (in this case) second time-varying measurement values ​​as follows: |U|·|I|·cos(φ U -φ I ), or |U| |I| cos(φ I -φ U ), where φ U = voltage phase, φ I = current phase. Essentially, the plasma ignition detection device 1 can also calculate a second reactive power from these second time-varying measurements as follows: |U| |I| sin(φ U -φ I ), or |U| |I| sin(φ I -φ U ), where φ U = voltage phase, φ I = current phase. In this case, the active power or reactive power is the second time-varying quantity.

[0123] The plasma ignition detection device 1 is configured to continually calculate new values ​​of the second time variation using new second time variation measurements.

[0124] In Fig. 5B, the second harmonic (1st harmonic) and optionally also the third harmonic (2nd harmonic) of the second time-varying measurement of current and voltage are determined. This is preferably done only at the second location, i.e. at the output 50b of the impedance matching circuit 50. The concept is not limited to measuring three harmonics. Basically, there are several more harmonics possible, provided they fit into the baseband.

[0125] To this end, the plasma ignition detection device 1 includes fifth and sixth I / Q demodulators 31,32 and, optionally, seventh and eighth I / Q demodulators 33,34.

[0126] The output of the third A / D converter 27 is connected to a fifth I / Q demodulator 31 and optionally also to a seventh I / Q demodulator 33 .

[0127] The output of the fourth A / D converter 28 is connected to a sixth I / Q demodulator 32 and optionally also to an eighth I / Q demodulator 34 .

[0128] The frequency of the fifth and sixth I / Q demodulators 31 , 32 is preferably set to twice the frequency of the HF generator 60 .

[0129] The frequency of the optional seventh and optional eighth I / Q demodulators 33 , 34 is preferably set to three times the frequency of the HF generator 60 .

[0130] The outputs of the fifth, sixth and optionally seventh and optionally eighth I / Q demodulators 31, 32, 33, 34 are connected to a signal conditioning device 25. The signal conditioning device 25 is arranged to perform one or more of the following operations: signal filtering, downsampling, error correction. The signal conditioning device 25 is further arranged to generate complex values ​​of the second and optionally third harmonics of the currents and voltages. These values ​​are preferably added to the respective values ​​of the first harmonic (fundamental) currents and voltages. This may result, for example, in a second time-varying measurement.

[0131] The plasma ignition detection device 1 is configured to set the clock rates of the third and fourth A / D converters 27, 28 such that the fundamental, the second harmonic (first harmonic) and optionally the third harmonic (second harmonic) of the HF generator 60 are generated, whereby the second harmonic and the optional third harmonic of the HF generator 60 are mirrored at the Nyquist frequency of the third and fourth A / D converters 27, 28 and are spaced apart from each other by a predetermined or maximum frequency range below the Nyquist frequency. This achievable spacing allows the signal conditioning device 25 to separate the respective signals (fundamental, mirrored second harmonic and optional mirrored third harmonic of current and voltage) from each other. Thereby, the second harmonic and the optional third harmonic can be analyzed independently of each other and of the fundamental, thereby allowing more accurate inductive inferences about the plasma state of the plasma 4. A / D converters 18, 21 of Figure 5A and A / D converters 27, 28 of Figure 5B preferably operate synchronously, i.e., connected to a synchronous clock signal 51 for example.

[0132] The plasma ignition detection device 1 is further configured to calculate a second harmonic (first harmonic) and an optional third harmonic (second harmonic) of the second reactive power and / or the active power.

[0133] The plasma ignition detection device 1 is configured to average a plurality of the first and / or second time-varying measurements to calculate a first time-varying quantity from the averaged first time-varying measurements and a second time-varying quantity from the averaged second time-varying measurements. Additionally or alternatively, the plasma ignition detection device 1 is configured to average a plurality of values ​​for the first time-varying quantity and a plurality of values ​​for the second time-varying quantity and to generate an output signal depending thereon.

[0134] The first and / or second time variation amounts are peak values ​​or average values ​​of a plurality of determined first and / or second time variation amounts.

[0135] The plasma ignition detection device 1 is configured to continuously calculate new values ​​for the first and second time change quantities using new first and second time change measurement values ​​and to generate new output signals depending on these new values.

[0136] FIG. 6 shows a graph from which it can be seen that high efficiency is evidence of the desired plasma state. In this case, the plasma 4 is ignited. From a given point in time, the input power P in It is shown that the input power P in is measured at a first point, namely at the input 50a of the impedance matching circuit 50. This measurement can be made via a directional coupler or via corresponding current and voltage sensors 15, 16. Apart from that, the output power P out The output power P out is measured at a second location, namely at the output 50b of the impedance matching circuit 50. The efficiency is above a certain threshold, so it can be assumed that the plasma 4 has been ignited. This is confirmed by the optical device 90 ("Ignition").

[0137] On the other hand, FIG. 7 shows a graph in which it can be seen that low efficiency is a hallmark of undesirable plasma conditions. In this case, the plasma 4 is not ignited. The efficiency is lower than in the graph of FIG. 6. The output power P out is also lower than the output power of the graph of FIG. 6. In this case, the optical device 90 does not detect the ignition of the plasma 4. This is consistent with the calculated efficiency. Basically, if the efficiency is below the first threshold, it can be said that the plasma 4 is not in the desired state. If the efficiency is equal to or higher than the second threshold, it can be said with high probability that the plasma 4 is in the desired state. The first and second thresholds can be the same. The second threshold can also be higher than the first threshold, so that for the range between the first and second thresholds, there is no clear indication of the plasma 4 and it is necessary to collect, for example, more first time-varying measurements and more second time-varying (measurements). In this case, for example, the second harmonic and the optional third harmonic can be analyzed in more detail.

[0138] The invention is not limited to the described embodiments.Within the scope of the invention, all features described and / or illustrated can be combined with one another in any desired manner. [Explanation of symbols]

[0139] 1. Plasma ignition detection device 5 First measuring unit 6 Second Measuring Unit 8 Memory Devices 9 AI Module 15 Current Sensor 16 Voltage Sensor 50 Impedance matching circuit 50a HF input section 50b HF output section 60 HF Generator 100 Plasma Generation System

Claims

1. A plasma ignition detection device (1) for connection to an impedance matching circuit (50) of a plasma generation system (100), the plasma ignition detection device (1) comprising: a) processing first time-varying measurements from a first predetermined location of the impedance matching circuit (50), whereby an applied first reactive and / or active power is ascertainable from the first time-varying measurements; b) processing a second time-varying value associated with a second location of the impedance matching circuit (50), the second location being different from the first predetermined location, and from the second value a second applied reactive power and / or active power is determinable; c) determining a first time variation from the first time varying measurement; d) determining a second time change from the second value; e) A plasma ignition detection device (1) configured to generate an output signal representative of a plasma state in dependence on said first and second time quantities.

2. The output signal is a) a control command for controlling the impedance matching circuit (50); and / or b) control commands for the HF generator (60) of said plasma generation system (100); and / or 2. The plasma ignition detection device (1) according to claim 1, characterized in that: c) an output message.

3. The plasma ignition detection device (1) includes a memory device (8), which stores various a) the first and second time changes, and / or b) the first and second reactive powers and / or active powers, and / or c) a ratio of the first and second reactive and / or active powers; A control command for the impedance matching circuit (50) and / or the HF generator (60) for The plasma ignition detection device (1) comprises: a) the current first and second time variations, and / or b) the first and second reactive powers and / or active powers currently being used, and / or c) a ratio of the first and second reactive powers and / or active powers at present; 3. The plasma ignition detection device (1) according to claim 2, characterized in that it is configured to load corresponding control commands for the impedance matching circuit (50) and / or the HF generator (60) from the memory device (8) based on the impedance matching circuit (50) and transmit them to the HF generator (60).

4. The plasma ignition detection device (1) includes an AI module (9), which comprises: a) the first and second time changes, and / or b) the first and second reactive powers and / or active powers, and / or c) a ratio of the first and second reactive and / or active powers; 3. The plasma ignition detection device (1) of claim 2, further comprising a control circuit (50) for generating said control commands for said impedance matching circuit (50) and / or said HF generator (60) based on:

5. The plasma ignition detection device (1) comprises: a) linking the first time variation and the second time variation to one another via at least one mathematical operation; and / or b) linking the first reactive power and / or the active power and the second reactive power and / or the active power with each other via at least one mathematical operation; generating said output signal dependent on the result; 5. The plasma ignition detection device (1) according to claim 1, characterized in that it is formed.

6. 6. The plasma ignition detection device (1) according to claim 5, characterized in that the plasma igniter detection device (1) is configured to divide the second reactive power and / or active power by the first reactive power and / or active power in order to calculate the efficiency and to generate the output signal in dependence on the efficiency.

7. The plasma ignition detection device (1) comprises: a) the first time change amount and / or the first reactive power and / or active power exceed a threshold value; and / or b) generating the output signal only if the second time variation and / or the second reactive power and / or active power exceed a threshold value.

8. The first time-varying quantity is reactive power or active power, and / or The plasma ignition detection device (1) according to any one of the preceding claims, characterized in that the second time-varying quantity is reactive power or active power.

9. The plasma ignition detection device (1) comprises: of the second reactive power and / or active power, a) the first harmonic, or b) the first and second harmonics; The plasma ignition detection device (1) further comprises: a) the first harmonic, or b) the first and second harmonics 9. The plasma ignition detection device (1) according to any one of the preceding claims, characterized in that it is adapted to generate said output signal in dependence on the electrical power of

10. the first predetermined location being in the region of an HF input (50a) of the impedance matching circuit (50) and the second location being in the region of an HF output (50b) of the impedance matching circuit (50); or The plasma ignition detection device (1) according to any one of claims 1 to 9, characterized in that the first predetermined location is in the area of ​​an HF output part (50b) of the impedance matching circuit (50) and the second location is in the area of ​​an HF input part (50a) of the impedance matching circuit (50).

11. a first measurement unit (5) is provided, the first measurement unit (5) being configured to determine the first time-varying measurement value at the first predetermined location of the impedance matching circuit (50), the determination being made by physical measurement; a second measuring unit (6) is provided, said second measuring unit (6) being adapted to determine a second time-varying value, a) the determination is made by physical measurement at the second location, such that the second time-varying value is a time-varying measurement; or b) the determination of the impedance matching circuit (50); and I) of the first time-varying measurement, and / or II) the first time change amount, The plasma ignition detection device (1) according to any one of the preceding claims, characterized in that it is carried out by calculation, on the basis of a physical model.

12. the first measurement unit (5) includes a directional coupler; and / or 12. Plasma ignition detection device (1) according to claim 11, characterized in that the second measurement unit (6) comprises a directional coupler.

13. the first time-varying measurement is the power of the incoming and outgoing waves, and the second time-varying measurement is the power of the outgoing and incoming waves; the plasma ignition detection device (1) is configured to subtract the power of the outgoing wave from the power of the incoming wave, thereby calculating the first time change amount, 13. The plasma ignition detection device (1) of claim 12, characterized in that the plasma ignition detection device (1) is configured to subtract the power of the incident wave from the power of the outgoing wave, thereby calculating the second time variation.

14. the first measurement unit (5) comprises a current sensor (15) and a voltage sensor (16), the first time-varying measurements being current and voltage; and / or The plasma ignition detection device (1) according to any one of claims 11 to 13, characterized in that the second measurement unit (6) comprises a current sensor (15) and a voltage sensor (16), and the second time-varying measurements are current and voltage.

15. the first time varying measurements are complex currents and complex voltages; and / or 15. The plasma ignition detection device (1) of claim 14, wherein the second time-varying measurements are complex currents and complex voltages.

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