Control device for controlling a plasma process supply system, a plasma process supply system having such a control device, and a method for operating a control device

Abstract

The invention relates to a control device (1) used for controlling a plasma process supply system (100). The plasma process supply system comprises an RF generator (101) and an impedance matching circuit (101) used for connection to a load (103). The control device (1) is designed to determine a supply power of the RF generator (101) and an output power of the impedance matching circuit (102). The control device (1) is designed to adjust the RF generator (101) and / or the impedance matching circuit (102), in particular to change the frequency of the RF generator (101), so that an overall efficiency of the plasma process supply system (100), which results from the determined supply power of the RF generator (101) and the output power of the impedance matching circuit (102), is increased.

Description

[0001] Control device for controlling a plasma process supply system, a plasma process supply system with such a control device and a method for operating a control device

[0002] The invention relates to a control device for controlling a plasma process supply system, a plasma process supply system with such a control device and a method for operating a control device.

[0003] The surface treatment of workpieces using plasma and gas lasers are industrial processes in which a plasma is generated, particularly in a plasma chamber, using direct current or a high-frequency alternating signal with an operating frequency in the range of a few 10 kHz up to 100 GHz.

[0004] The plasma chamber is connected to a high-frequency generator (HF generator) via additional electronic components such as coils, capacitors, cables, or transformers. These additional components can represent resonant circuits, filters, or impedance matching circuits.

[0005] The plasma process has the problem that the electrical load impedance of the plasma chamber (the plasma = consumer) that occurs during the process depends on the conditions in the plasma chamber and can vary greatly. In particular, the properties of the workpiece, electrodes, and gas conditions are important.

[0006] High-frequency generators have a limited operating range with respect to the impedance of the connected electrical load (= consumer). If the load impedance exceeds a permissible range, damage or even destruction of the RF generator can occur. For this reason, an impedance matching circuit (matchbox) is usually required to transform the load impedance to a nominal impedance of the generator output.

[0007] Various impedance matching circuits are known. Either the impedance matching circuits are fixed and have a predetermined transformation effect, i.e., they consist of electrical components, particularly coils and capacitors, that do not change during operation. This is particularly useful for constant operation, such as in a gas laser. Furthermore, impedance matching circuits are known in which at least some of the components of the impedance matching circuits are mechanically variable. For example, motor-driven variable capacitors are known, whose capacitance value can be changed by changing the arrangement of the capacitor plates relative to one another.

[0008] Roughly speaking, a plasma can be assigned three impedance ranges. Before ignition, very high impedances exist. During normal operation, i.e., during intended operation with plasma, lower impedances exist. Very low impedances can occur in the case of undesired local discharges (Ares) or plasma fluctuations. In addition to these three identified impedance ranges, other special states with other associated impedance values ​​can occur. If the load impedance changes suddenly and the load impedance or the transformed load impedance moves outside of a permissible impedance range, the RF generator or transmission equipment between the RF generator and the plasma chamber can be damaged. Furthermore, there are also stable plasma states that are undesirable. An impedance matching circuit is described, for example, in DE 10 2009 001.

[0009] 355 Al described.

[0010] It is also known that plasma processes require a great deal of energy, which is playing an increasingly important role these days. Losses arise primarily from high reactive currents flowing in the impedance matching circuit, reducing its efficiency. To transfer the desired power to the plasma, the high-frequency generator must therefore provide a higher output power, which further increases power loss.

[0011] It is therefore the object of the present invention to establish a plasma process that is as energy-efficient as possible.

[0012] The object is achieved by a control device for controlling a plasma process supply system according to claim 1, by a plasma process supply system according to claim 17, and by a method for operating the control device according to claim 20. Claims 2 to 16 describe advantageous embodiments of the control device, and claims 18 and 19 describe advantageous embodiments of the plasma process supply system.

[0013] The control device according to the invention serves to control a plasma supply system, which comprises an RF generator and an impedance matching circuit and is used for connection to a load, in particular to a plasma chamber. The control device is designed to determine a supply power of the RF generator and an output power of the impedance matching circuit. The term "supply power" refers in particular to the power required to operate the RF generator. This is in particular the power that the at least one power supply of the RF generator draws from or outputs from the (public) power grid. If the RF generator has multiple power supplies, the "supply power" is the sum of the powers that the power supplies of the RF generator draw from or output from the (public) power grid.The term "output power" refers to the power that results from the power supplied by the RF generator and is output by the impedance matching circuit. If multiple signals from different RF generators or DC generators are supplied to the impedance matching circuit, the signals from the other RF generators or DC generators should be disregarded when determining the output power. These other signals can be disregarded particularly easily because they have a different frequency. The control device is further configured to adjust the RF generator and / or the impedance matching circuit in such a way, in particular by changing the frequency of the RF generator, that the overall efficiency of the plasma process supply system, which results from the determined supply power of the RF generator and the output power of the impedance matching circuit, is increased.

[0014] It is particularly advantageous here that the control device is designed to regulate the RF generator and / or the impedance matching circuit to optimize the overall efficiency. The control device is designed to determine the overall efficiency based on the supply power of the RF generator and the output power of the impedance matching circuit. The control device therefore takes both the RF generator and the impedance matching circuit into account. Therefore, no individual optimization of the RF generator or the impedance matching circuit takes place. Studies have shown that even a reduction in the efficiency of the impedance matching circuit, which is determined from an input power and an output power of the impedance matching circuit, can lead to an increase in overall efficiency if the RF generator or the impedance matching circuit are adjusted accordingly.In other words, a reduction in the efficiency of one component (RF generator or impedance matching circuit) can be accepted because at the same time the efficiency of the other component increases significantly more and the overall efficiency improves.

[0015] Control devices are described in the prior art, in particular in US10818477B2, US20210134563A1 and US20180053633A1.

[0016] In an advantageous embodiment, the control device is designed to calculate the overall efficiency of the plasma process supply system based on the determined supply power and the output power. In particular, the output power is divided by the supply power. It is conceivable that a plurality of measured values ​​for the supply power and the output power are averaged before the overall efficiency is calculated.

[0017] In an advantageous embodiment, the control device is designed to determine the output power of the RF generator, in particular the forward power and the return power or a quantity related to the return power.

[0018] In an advantageous embodiment, the control device is designed to adjust, in particular regulate, the output power of the RF generator. The regulation can be carried out, for example, in such a way that the returning power is minimized or falls below a threshold value.

[0019] In an advantageous embodiment, the control device is designed to change the frequency of the RF generator during operation, in particular continuously. A frequency change can occur, for example, more than 5 times, 10 times, 100 times, 200 times, 500 times, or more than 1000 times per second. The control device is further designed, in particular, to continuously check whether the overall efficiency improves after a frequency change. This continuous check can occur, for example, more than 5 times, 10 times, 100 times, 200 times, 500 times, or more than 1000 times per second. Preferably, the continuous check always occurs after a change in frequency, wherein further preferably a certain period of time is waited after the change in frequency before checking the overall efficiency. As a result, the overall efficiency can always be optimized during operation.Changing the frequency of the RF generator is also very simple and quick. The control device is preferably designed to change the frequency of the RF generator only within a certain range. This range is preferably selected depending on the amplifier elements used. This ensures that the RF generator is not operated outside its specifications, which could, for example, lead to damage to the RF generator.

[0020] In an advantageous embodiment, the control device is configured to further change the frequency in the same direction if the overall efficiency has improved. For example, if the frequency is increased and the overall efficiency improves as a result, the frequency is further increased in a subsequent step. Additionally or alternatively, the control device is configured to change the frequency in the opposite direction if the overall efficiency has deteriorated. For example, if the frequency is increased and the overall efficiency deteriorates as a result, the frequency is reduced in a subsequent step.

[0021] In an advantageous embodiment, the control device is designed to select a step size with which the frequency of the signal output by the RF generator to the impedance matching circuit is changed, depending on a change in the overall efficiency. Preferably, the larger the step size, the greater the change in the overall efficiency. This results in a rapid system settling.

[0022] In an advantageous embodiment, the control device is designed to adjust the frequency only within a specific frequency range. This frequency range can preferably be specified by a user and / or a driver for controlling the RF generator.

[0023] This prevents the RF generator from operating outside its specifications.

[0024] In an advantageous embodiment, the control device comprises a Kl module that is trained by the manufacturer to adjust the RF generator and / or the impedance matching circuit, in particular to change the frequency of the RF generator, at least based on the supply power and the output power. During training, different values ​​for the supply power of the RF generator and the output power of the impedance matching circuit are supplied to the Kl module. At the same time, the Kl module is informed of the frequency at which the RF generator is to be operated, or whether the frequency at which the RF generator is to be operated should be increased, decreased, or left the same. Additionally or alternatively, the Kl module can also be informed of how the impedance matching circuit is to be adjusted, in particular how the transformation ratio is to be selected. The entire process can also be made dependent on the current plasma process.During operation, the supply power of the RF generator and the output power of the impedance matching circuit are fed to the KL module. This occurs at the input node. The type of the respective plasma process can also be fed to the KL module at the input node. The KL module comprises a plurality of intermediate nodes and at least one output node, at which the frequency to be set for the HF generator can be output, or the information as to whether the frequency should be increased or decreased. Additionally or alternatively, the transformation ratio of the impedance matching circuit can be output, or the information as to whether the transformation ratio should be increased or decreased, can be output at the at least one output node.

[0025] In an advantageous embodiment, the control device is designed to change the frequency of the RF generator only when the overall efficiency exceeds a threshold value. "Exceeding" here means both a transition from larger to smaller or from smaller to larger values. This prevents the frequency from being constantly changed. Additionally or alternatively, this can also apply to a change in the transformation ratio of the impedance matching circuit. If the overall efficiency is greater than 70%, for example, a change in the frequency of the RF generator and / or a change in the transformation ratio of the impedance matching circuit can be dispensed with.

[0026] In an advantageous embodiment, the control device is configured to control the impedance matching circuit such that a transformation ratio between an input impedance of the impedance matching circuit and an output impedance of the impedance matching circuit can be changed during operation. The control device is further configured to check whether the overall efficiency improves after changing the transformation ratio. The input impedance and / or the output impedance of the impedance matching circuit can change. However, this is not mandatory.

[0027] In an advantageous embodiment, the control device is designed to control the impedance matching circuit such that the input impedance and / or the output impedance remains unchanged upon a change in the transformation ratio. For this purpose, the impedance matching circuit preferably comprises at least one transformation stage, so that the input impedance is transformed to at least one first intermediate impedance, which is then in turn transformed to the output impedance. The input impedance can still correspond to the nominal impedance of the RF generator, such as 50 ohms, and the output impedance can still correspond to the plasma impedance. By changing the transformation ratio from the input impedance to the at least one first intermediate impedance, the overall efficiency can nevertheless be increased.

[0028] In an advantageous embodiment, the impedance matching circuit comprises a first transformation stage configured to transform an input impedance into a first intermediate impedance. The impedance matching circuit may comprise a second transformation stage configured to transform the first intermediate impedance into a second intermediate impedance. The impedance matching circuit may comprise a third transformation stage configured to transform the second intermediate impedance into an output impedance.The control device is designed to control the impedance matching circuit in such a way that, for a given input and output impedance, the transformation path of the first transformation stage and / or the second transformation stage and / or the third transformation stage changes, wherein the control device redetermines the overall efficiency of the plasma process supply system after such a change.

[0029] In an advantageous embodiment, the supply power is active power. Additionally or alternatively, the output power is active power.

[0030] In an advantageous embodiment, the control device comprises a first measuring unit. The first measuring unit is designed to determine the supply power from an alternating voltage and an alternating current that can be obtained from the (public) power grid and are present at the input of a power supply of the RF generator. In this case, the efficiency of at least one power supply of the RF generator is also included in the overall efficiency. Alternatively, the first measuring unit is designed to determine the supply power from a direct voltage and a direct current that are present at the output of the power supply of the RF generator and serve to supply at least one RF amplifier of the RF generator. In this case, the supply power can be determined more easily.The at least one power supply unit is particularly designed to transform a mains supply voltage with a frequency of, for example, 50 Hz or 60 Hz into a regulated DC voltage, which can also be referred to as an intermediate circuit voltage. This DC voltage is then fed to the at least one RF amplifier, which converts it into RF power to amplify an RF signal.

[0031] In an advantageous embodiment, the control device comprises at least one second measuring unit. The second measuring unit comprises at least one directional coupler or a current sensor and a voltage sensor. The control device is designed to determine the output power based on the measurement results of the at least one directional coupler or the current sensor and the voltage sensor.

[0032] In an advantageous embodiment, the second measuring unit can be arranged at the output of the impedance matching circuit. Alternatively, the second measuring unit can be arranged at the input of the impedance matching circuit, and the control device is configured to determine the output power based on the current transformation ratio of the impedance matching circuit.

[0033] In an advantageous embodiment, the voltage sensor of the second measuring unit is a capacitive voltage divider, with a first capacitance formed by an electrically conductive ring or cylinder through which a cable can be routed, along which the RF power can be transmitted. In addition, the current sensor of the second measuring unit is a coil arranged around the conductive ring or cylinder. This design enables contactless measurement of current and voltage.

[0034] In an advantageous embodiment, the control device is designed to determine a reflection factor, in particular at the output of the RF generator. The control device is designed to adjust the RF generator and / or the impedance matching circuit, in particular to change the frequency of the RF generator, so that the reflection factor is reduced, wherein the control device is further designed to adjust the RF generator and / or the impedance matching circuit such that the reflection factor is increased while simultaneously improving the overall efficiency. It is particularly advantageous that an increasing reflection factor is also permitted while simultaneously improving the overall efficiency.

[0035] The plasma process supply system according to the invention comprises the control device described above. The plasma supply system has an RF generator and an impedance matching circuit. The RF generator is connected to the impedance matching circuit via a first cable connection. The impedance matching circuit can be connected to a load, in particular in the form of a plasma chamber, via a second cable connection. It is particularly advantageous for the control device to function as a type of central control device and control both the RF generator and the impedance matching circuit.

[0036] In an advantageous embodiment of the plasma process supply system, the RF generator has at least one power supply and at least one RF amplifier. The at least one power supply comprises an input for connection to a (public) power grid and an output for connection to the at least one RF amplifier. The at least one power supply is designed to convert an AC voltage at the input into a (regulatable) DC voltage and to output the DC voltage at the output and feed it to the at least one RF amplifier. The control device is designed to determine the supply power at the input or at the output or between the input and the output.

[0037] In an advantageous embodiment of the plasma process supply system, the impedance matching circuit comprises at least one or more adjustable reactances to change the transformation ratio for the impedance between an input to which the RF generator is connected and an output to which the load can be connected. The reactances are mechanically adjustable and / or electrically adjustable and are formed in particular by at least one varactor and / or at least one switchable inductance and / or capacitance and / or at least one PIN diode. If the reactance is a capacitance, its magnitude can be changed, for example, by motorized adjustment of the plate spacing. The term "adjustable" can also be understood to mean connecting and / or disconnecting a reactance.

[0038] The method according to the invention serves to operate the control device mentioned above for controlling the plasma supply system with an RF generator and an impedance matching circuit. In a first method step, the supply power of the RF generator is determined. Furthermore, the output power of the impedance matching circuit is determined. In a second method step, the RF generator is adjusted, in particular by changing the frequency of the RF generator. Additionally or alternatively, the impedance matching circuit is adjusted. This increases the overall efficiency of the plasma process supply system, which results from the determined supply power of the RF generator and the output power of the impedance matching circuit.

[0039] The invention is described below purely by way of example with reference to the drawings. They show:

[0040] Figure 1: an embodiment of the plasma process supply system according to the invention with a control device according to the invention;

[0041] Figures 2A, 2B: various embodiments of how an impedance matching circuit can be constructed;

[0042] Figures 3, 4: embodiments of how a measuring unit for measuring a current and a voltage can be designed;

[0043] Figure 5: an example of an example of efficiency curves; and

[0044] Figure 6: a flowchart for a method illustrating the operation of the

[0045] Control device explained.

[0046] Figure 1 shows a plasma process supply system 100, which comprises a control device 1. The plasma generation system 100 further comprises an RF generator 101, an impedance matching circuit 102, and at least one consumer 103, in particular in the form of a plasma chamber. The RF generator 101 is designed to provide an RF signal, in particular in the form of a CW signal, with a nominal power PNenn and a frequency fo and to output it at an output terminal 101a. The impedance matching circuit 102 comprises an input terminal 102a, wherein the RF generator 101 is connected to the input terminal 102a via a first cable connection 104a. The impedance matching circuit 102 further comprises an output terminal 102b. The output terminal 102b is connected to the at least one consumer 103 via a second cable connection 104b.The first and / or second cable connection 104a, 104b may comprise one or more cables, for example, connected in series and / or in parallel. Coaxial cables are preferably used.

[0047] The load 103, i.e., the plasma chamber, comprises at least one electrode 105 for generating a plasma 106. The electrode 105 is (galvanically) connected to the output terminal 102b of the impedance matching circuit 102. In this exemplary embodiment, a camera system 107 is also arranged in the plasma chamber, which is designed to observe the plasma 106.

[0048] The control device 1 is preferably a processor and / or FPGA and / or microcontroller and / or ASIC. The control device 1 can also include a memory unit.

[0049] The control device 1 is designed to control the RF generator 101, in particular to activate or deactivate it. Additionally or alternatively, the control device 1 is also designed to change the power and / or frequency of the RF signal by appropriately controlling the RF generator 101. Additionally or alternatively, the control device 1 is designed to change the waveform (type of RF signal, modulation of the RF signal) of the RF signal by appropriately controlling the RF generator 101.

[0050] The RF generator 101 comprises a power supply 109, which is designed to transform an alternating current into a (regulated) direct current and an alternating voltage into a (regulated) direct voltage. The RF generator 101 also comprises a signal generating device 110 and an RF amplifier 111. The signal generating device 110 is designed, in particular, to generate the CW signal and output it to the RF amplifier 111. The RF amplifier 111 is designed to amplify the CW signal to a specific level and to transmit it to the impedance matching circuit 102 via the output terminal 101a. The RF amplifier 111 is powered by the power supply 109.

[0051] The control device 1 is preferably also designed to control the impedance matching circuit 102. In particular, the control device 1 is designed to change the transformation ratio within the impedance matching circuit 102.

[0052] The control device 1 also comprises a first measuring unit 2. The first measuring unit 2 is designed to determine the supply power from an alternating voltage and an alternating current that the power supply 109 of the RF generator 101 draws from the (public) power grid. Alternatively, the first measuring unit 2 is designed to determine the supply power from a direct voltage and a direct current that are provided at the output of the power supply 109 of the RF generator 101 and used to supply the at least one RF amplifier 111. The first measuring unit 2 can, for example, comprise a shunt resistor for measuring the direct current and, for example, a voltage divider for measuring the direct voltage.

[0053] The control device 1 also comprises a second measuring unit 3. The second measuring unit 3 comprises at least one directional coupler or a current sensor 5 and a voltage sensor 6. A configuration with a current sensor 5 and a voltage sensor 6 is illustrated in Figures 3 and 4. The control device 1 is designed to determine, in particular calculate, the output power at the output of the impedance matching circuit 102 based on the measurement result of the at least one directional coupler or the current sensor 5 and the voltage sensor 6. In Figure 1, the second measuring unit 3 is arranged at the output of the impedance matching circuit 102.The second measuring unit 3 could also be arranged at the input of the impedance matching circuit 102, wherein the control device 1 is in this case designed to determine the output power at the output terminal 102b of the impedance matching circuit 102 based on the current transformation ratio of the impedance matching circuit 102.

[0054] The supply power is preferably active power. The output power is also preferably active power.

[0055] As explained, the control device 1 is designed to determine, in particular to measure, a supply power of the RF generator 101 and an output power of the impedance matching circuit 102. The control device 1 is then designed to adjust the RF generator 101 and / or the impedance matching circuit 102, in particular to change the frequency of the RF generator 101, such that the overall efficiency of the plasma process supply system 100, which results from the determined supply power of the RF generator 101 and the output power of the impedance matching circuit 102, is increased.

[0056] The plasma generation system 100 preferably also includes an operating unit 108. The operating unit 108 is preferably a screen, in particular a touch-sensitive screen. In addition to a screen, the operating unit 108 can also include input devices such as a keyboard and / or mouse. The operating unit 108 can also be a web server that provides data and receives user input. The control device 1 is designed to display current settings of the RF generator 101 and / or the impedance matching circuit 1 on the operating unit 108.

[0057] The control device 1 can also be configured to display the measured values ​​received by the first and / or second measuring unit 2, 3, such as the supply power or the output power, on the operating unit 108. The determined overall efficiency can also be displayed by the control device 1 on the operating unit 108. The control device 1 is preferably configured to receive setpoint specifications, for example for the power of the RF signal, the frequency of the RF signal, and / or the waveform of the RF signal, from the operating unit 108 and to generate corresponding manipulated variables for the RF generator 101 and transmit them to it.

[0058] The control device 1 can be configured to change the frequency of the RF generator 101 during operation, in particular continuously. The control device 1 can further be configured to check, in particular continuously, whether the overall efficiency improves or not after a frequency change.

[0059] The control device 1 can be configured to further change the frequency of the RF generator 101 in the same direction as during a previous frequency change if the overall efficiency has improved since the previous frequency change. If this is not the case, the control device 1 can be configured to change the frequency in the opposite direction.

[0060] The control device 1 can also be configured to select a step size with which the frequency of the RF generator 101 is changed depending on a change in the overall efficiency. If the overall efficiency increases significantly after a frequency change (higher than a first threshold), the step size for the next frequency change can be increased. If the overall efficiency increases less significantly after a frequency change (below a second or the first threshold), the step size for the next frequency change can be selected to be smaller.

[0061] In principle, the control device 1 is designed solely to set the frequency within a specific frequency range. The RF generator 101 can also perform such a plausibility check in addition or as an alternative.

[0062] The control device 1 can also be designed to carry out the control for increasing the overall efficiency only if the overall efficiency falls below a certain level.

[0063] In Figure 1, the control device 1 also includes a Kl module 4. The Kl module 4 is trained by the manufacturer to adjust the RF generator 101 and / or the impedance matching circuit 102 based at least on the supply power and the output power, and optionally based on the plasma process, in such a way that the overall efficiency is increased. However, the use of a Kl module 4 is optional.

[0064] The impedance matching circuit 102 is also designed to transform an input impedance at its input terminal 102a to an output impedance at its output terminal 102b. For this purpose, the impedance matching circuit 102 preferably comprises at least a first transformation stage 112a. In the exemplary embodiment shown in Figure 1, the impedance matching circuit 102 comprises a first, second, and a third transformation stage 112a, 112b, 112c. The first transformation stage 112a is designed to transform an input impedance into a first intermediate impedance. The second transformation stage 112b is designed to transform the first intermediate impedance into a second intermediate impedance. The third transformation stage 112c is designed to transform the second intermediate impedance into an output impedance.The control device 1 is designed to control the impedance matching circuit 102 such that, for a given input and output impedance, the transformation path of the first transformation stage 112a and / or the second transformation stage 112b and / or the third transformation stage 112c changes, wherein the control device 1 redetermines the overall efficiency of the plasma process supply system after such a change. Preferably, the input impedance and the output impedance remain unchanged. Only the transformation path from the input impedance to the first intermediate impedance or from the first intermediate impedance to the second intermediate impedance or from the second intermediate impedance to the output impedance changes. The impedance values ​​of the first intermediate impedance and the second intermediate impedance can be changed.

[0065] Figures 2 and 3 show various embodiments of the impedance matching circuit 102. The impedance matching circuit 102 can contain precisely one transformation stage 112a, which can be constructed according to the example in Figures 2A, 2B. If the impedance matching circuit 102 contains multiple transformation stages 112a, 112b, 112c, each transformation stage 112a, 112b, 112c can be constructed according to the embodiment in Figures 2A, 2B. It is clear that the impedance matching circuit 102 can also be constructed differently than shown in Figures 2A, 2B.

[0066] In Figure 2A, the input terminal 102a of the impedance matching circuit 102 is connected to a first coil 113 (first inductance) and to a second coil 114 (second inductance). The first terminals of the first and second coils 113, 114 are connected to a common node and thus to the input terminal 102a of the impedance matching circuit 102. The first coil 113 is connected to a reference ground via a first capacitor 115 (first capacitance). The second coil 114 is connected to the output terminal 102b via a second capacitor 116 (second capacitance). The first and / or second capacitors 115, 116 are adjustable components, in particular in the form of variable capacitors whose capacitance can be changed via stepper motors. Alternatively, solid-state switches can be used to switch capacitances on and off as quickly as possible.In particular, the plate spacing of the first and second capacitors 115, 116 can be changed. The control device 1 is designed to control the respective stepper motors accordingly. The capacitances of the first and second capacitors 115, 116 can be adjusted independently of one another. Preferably, the impedance matching circuit 102 is free of additional components. Of course, the position of the first coil 113 and the first capacitor 115 can also be swapped. In this case, the first capacitor 115 is arranged at the input terminal 102a of the impedance matching circuit 102, and the first coil 113 is arranged at the reference ground. Additionally or alternatively, the position of the second coil 114 and the second capacitor 116 can also be swapped. In this case, the second capacitor 116 is arranged at the input terminal 102a of the impedance matching circuit 102 and the second coil 114 is arranged at the output terminal 102b of the impedance matching circuit 102.

[0067] In Figure 2B, the input terminal 102a of the impedance matching circuit 102 is connected to the first capacitor 115 (first capacitance). The first capacitor 115 is connected to both the first coil 113 (first inductance) and the second coil 114 (second inductance). This occurs via a common node to which both the first capacitor 115 and the first and second coils 113, 114 are connected. The first coil 113 is also connected to the reference ground. The second coil 114 is connected to the second capacitor 116 (second capacitance) (series connection). The second capacitor 116 is connected to the output terminal 102b of the impedance matching circuit 102. The position of the second coil 114 and the second capacitor 116 could also be reversed. In this case, the second capacitor 116 would be connected to the common node and the second coil 114 would be connected to the output terminal 102b of the impedance matching circuit 102.Preferably, the impedance matching circuit 102 is free of additional components.

[0068] Figures 3 and 4 show an exemplary embodiment of a possible structure of the second measuring unit 3. In principle, the first measuring unit 2 can be constructed identically or similarly to the second measuring unit 3. In this exemplary embodiment, the second measuring unit 3 is designed to measure a voltage and a current without contact.

[0069] For this purpose, the second measuring unit 3 comprises a current sensor 5 and a voltage sensor 6.

[0070] However, it is still preferable to measure the phase relationship between current and voltage so that the impedance can be calculated.

[0071] The current sensor 5 of the second measuring unit 3 is a coil, in particular in the form of a Rogowski coil. Both ends of the coil are preferably connected to each other via a shunt resistor 7. The voltage drop across the shunt resistor 7 can be digitized using a first A / D converter 8.

[0072] The voltage sensor 6 of the second measuring unit 3 is preferably designed as a capacitive voltage divider. A first capacitor 9 is formed by an electrically conductive ring 9. An electrically conductive cylinder could also be used. The corresponding first and second cable connections 104a, 104b are routed through this electrically conductive ring 9. A second capacitor 10 of the voltage sensor 6, which is designed as a voltage divider, is connected to the reference ground. A second A / D converter 11 is connected in parallel to the second capacitor 10 and is designed to detect and digitize the voltage drop across the second capacitor 10.

[0073] In principle, the second measuring unit 3 can also be arranged or constructed on a (common) printed circuit board. The first capacitor 9 can be formed by a coating on a first and an opposite second side of the printed circuit board. In this case, the coatings on the first and second sides are electrically connected to one another by vias. The first and second cable connections 104a, 104b, respectively, are routed through an opening in the printed circuit board. The second capacitor 10 can be formed by a discrete component.

[0074] The current sensor 5 in the form of a coil, in particular in the form of a Rogowski coil, is spaced further from the first or second cable connection 104a, 104b than the first capacitor 9. The coil can also be formed on the same circuit board by appropriate coatings and vias. The coil for current measurement and the first capacitor for voltage measurement preferably extend through a common plane.

[0075] The shunt resistor 7 can also be arranged on this circuit board. The same applies to the first and / or second A / D converters 8, 11.

[0076] The first and / or second measuring unit 2, 3 can also be designed as directional couplers.

[0077] Fig. 5 shows, by way of example, the temporal progression of some signals of such a plasma process supply system 100 during operation. The upper graph shows the progression of the reflection factor Pr / Pi in a curve 16 over time t. The lower graph shows the simultaneous progressions of various efficiencies f| over time t. A first curve 18 can, for example, represent the progression of the efficiency of the impedance matching circuit 102. A second curve 19 can, for example, represent the progression of the efficiency of the RF generator. A third curve 20 can, for example, represent the progression of the overall efficiency of the plasma process supply system. The reflection factor moves from an initial value close to 30% to a value close to 0% at time t1. This could, for example, be the progression when the plasma process supply system 100 is switched on.At time t2, it rises slightly again, and at time t3, it rises slightly again, remaining constant but greater than 0% from time t4 onward. Such behavior of a reflection factor is usually undesirable. According to current rules, it would actually be desirable for it to remain as close to 0% as possible throughout the entire operating time, as between times t1 and t2. However, according to the invention, a different value is prioritized in the control process, as explained again below.

[0078] Between the start and the time t1, the efficiencies of the impedance matching circuit 102 and the RF generator 101 change, and thus the overall efficiency of the plasma process supply system 100.

[0079] At time t2, the efficiency of the RF generator 101 begins to increase further due to a change in the setting of the RF generator 101 and / or the impedance matching circuit 102, in particular a change in the frequency of the RF generator 101. At the same time, the efficiency of the impedance matching circuit 102 remains constant. This need not necessarily be the case, but is presented as such here for the sake of clarity. As a result, the overall efficiency increases further. The fact that the reflection factor increases slightly at the same time is accepted. This setting is triggered by the control device 1, which controls the RF generator 101 and / or the impedance matching circuit 102 accordingly. At time t3, the efficiency of the impedance matching circuit begins to increase further by changing the setting of the RF generator 101 and / or the impedance matching circuit 102, in particular by changing the frequency of the RF generator 101.At the same time, the efficiency of the RF generator 101 remains constant. This isn't necessarily the case, but is presented as such for clarity. This further increases the overall efficiency. The fact that the reflection factor simultaneously increases slightly again is accepted. This further adjustment is again triggered by the control device 1, which controls the RF generator 101 and / or the impedance matching circuit 102 accordingly.

[0080] From time t4 onward, no further improvement in overall efficiency can be achieved. The reflection factor can also no longer be improved without further deteriorating overall efficiency. This setting is therefore retained.

[0081] In another embodiment, it is also conceivable that the reflection factor is close to or equal to zero in the time interval between t3 and t4, and this is nevertheless the time range in which the overall efficiency of the plasma process supply system is highest.

[0082] Figure 6 describes the method according to the invention for operating the control device 1 for controlling the plasma process supply system 100. In a first method step S1, a supply power of the RF generator 101 and an output power of the impedance matching circuit 102 are determined. In a second method step S2, the RF generator 101, in particular by changing the frequency of the RF generator 101, and / or the impedance matching circuit 102 are adjusted such that an overall efficiency of the plasma process supply system 100, which results from the determined supply power of the RF generator 101 and the output power of the impedance matching circuit 102, is increased. The invention is not limited to the described exemplary embodiments.

[0083] Within the scope of the invention, all described and / or drawn features can be combined with one another as desired.

Claims

Claims 1. Control device (1) for controlling a plasma process supply system (100) with an RF generator (101) and an impedance matching circuit (101) for connection to a load (103), wherein the control device (1) has the following features: - the control device (1) is designed to determine a supply power of the RF generator (101) and an output power of the impedance matching circuit (102); - the control device (1) is designed to control the HF generator (101) and / or the impedance matching circuit (102) in such a way, in particular to change the frequency of the RF generator (101), that an overall efficiency of the plasma process supply system (100), which results from the determined supply power of the RF generator (101) and the output power of the impedance matching circuit (102) is increased.

2. Control device (1) according to claim 1, characterized by the following feature: - the control device (1) is designed to calculate the overall efficiency of the plasma process supply system (100) based on the determined supply power and the output power.

3. Control device (1) according to claim 1 or 2, characterized by the following feature: - the control device (1) is designed to change the frequency of the RF generator (101) during operation, in particular continuously, wherein the control device (1) is further designed to check, in particular continuously, whether the overall efficiency improves after a frequency change or not.

4. Control device (1) according to claim 3, characterized by the following feature: - the control device (1) is designed to change the frequency further in the same direction if the overall efficiency has improved; and / or - the control device (1) is designed to change the frequency in the opposite direction if the overall efficiency has deteriorated.

5. Control device (1) according to claim 3 or 4, characterized by the following feature: - the control device (1) is designed to select a step size with which the frequency is changed as a function of a change in the overall efficiency.

6. Control device (1) according to one of claims 3 to 5, characterized by the following feature: - the control device (1) is designed to set the frequency only in a specific frequency range.

7. Control device (1) according to one of claims 3 to 6, characterized by the following feature: - the control device (1) comprises a Kl module (4) which is trained by the manufacturer to adjust the RF generator (101) and / or the impedance matching circuit (102) at least on the basis of the supply power and the output power, in particular to change the frequency of the RF generator (101).

8. Control device (1) according to one of claims 3 to 7, characterized by the following feature: the control device (1) is designed to change the frequency of the RF generator (101) only when the overall efficiency exceeds a threshold value.

9. Control device (1) according to one of the preceding claims, characterized by the following feature: - the control device (1) is designed to control the impedance matching circuit (102) in such a way that a transformation ratio between an input impedance of the impedance matching circuit (102) and an output impedance of the impedance matching circuit (102) can be changed during operation, wherein the control device (1) is further designed to check whether the overall efficiency improves after a change in the transformation ratio or not.

10. Control device (1) according to claim 9, characterized by the following feature: - the control device (1) is designed to control the impedance matching circuit (102) in such a way that the input impedance and / or the output impedance remains unchanged when the transformation ratio changes.

11. Control device (1) according to one of the preceding claims, characterized by the following feature: - the supply power is active power and / or the output power is active power.

12. Control device (1) according to one of the preceding claims, characterized by the following features: - the control device (1) comprises a first measuring unit (2); - the first measuring unit (2) is designed to determine the supply power from an alternating voltage and an alternating current which can be obtained from the power grid and which is present at the input of a power supply unit (109) of the RF generator (101); or the first measuring unit (2) is designed to determine the supply power from a direct voltage and a direct current which are present at the output of the power supply unit (109) of the RF generator (101) and serve to supply at least one RF amplifier (111) of the RF generator (101).

13. Control device (1) according to one of the preceding claims, characterized by the following features: - the control device (1) comprises a second measuring unit (3); - the second measuring unit (3) comprises at least one directional coupler or a current sensor (5) and a voltage sensor (6); - the control device (1) is designed to determine the output power based on the measurement result of the at least one directional coupler or the current sensor (5) and the voltage sensor (6).

14. Control device (1) according to claim 13, characterized by the following features: - the second measuring unit (3) can be arranged at the output of the impedance matching circuit (102); or - the second measuring unit (3) can be arranged at the input of the impedance matching circuit (102) and the control device (1) is designed to determine the output power on the basis of the current transformation ratio of the impedance matching circuit (102).

15. Control device (1) according to claim 13 or 14, characterized by the following features: - the voltage sensor (6) of the second measuring unit (2) is a capacitive voltage divider, wherein a first capacitance (9) is electrically conductive ring or cylinder through which a cable (104b) can be passed, on which the RF power can be transmitted; - the current sensor (5) of the second measuring unit (3) is a coil arranged around the conductive ring (6) or cylinder.

16. Control device (1) according to one of the preceding claims, characterized by the following features: - the control device (1) is designed to determine a reflection factor, in particular at the output of the RF generator (101); - the control device (1) is designed to adjust the RF generator (101) and / or the impedance matching circuit (102) in such a way, in particular to change the frequency of the RF generator (101), that the reflection factor is reduced, wherein the control device (1) is further designed to adjust the RF generator (101) and / or the impedance matching circuit (102) in such a way that the reflection factor is increased while simultaneously improving the overall efficiency.

17. Plasma process supply system (100) with a control device (1) according to one of the preceding claims, characterized by the following features: - the plasma process supply system (100) comprises an RF generator (101) and an impedance matching circuit (102); - the RF generator (101) is connected to the impedance matching circuit (102) via a first cable connection (104a); - the impedance matching circuit (102) can be connected to a load (103), in particular in the form of a plasma chamber, via a second cable connection (104b).

18. Plasma process supply system (100) according to claim 17, characterized by the following features: - the RF generator (101) has at least one power supply (109) and at least one RF amplifier (111); - the at least one power supply (109) comprises an input for connection to a power network and an output for connection to the at least one RF amplifier (111); - the at least one power supply unit (109) is designed to convert an alternating voltage at the input into a direct voltage and to output the direct voltage at the output and to supply it to the at least one RF amplifier (111); - the control device (1) is designed to determine the supply power at the input or at the output or between the input and the output.

19. Plasma process supply system (100) according to claim 17 or 18, characterized by the following features: - the impedance matching circuit (102) comprises at least one or more adjustable reactances in order to change the transformation ratio for the impedance between an input to which the RF generator (101) is connected and an output to which the load (103) can be connected; - the reactances are mechanically adjustable and / or electrically adjustable and are formed in particular by at least one varactor and / or at least one switchable inductance and / or capacitance (115, 116) and / or by at least one PIN diode.

20. Method for operating a control device (1), in particular according to claims 1 to 16, for controlling a plasma process supply system (100), in particular according to claims 17 to 19, for connection to a load (103) with an RF generator (101) and an impedance matching circuit (102), comprising the following method steps: - determining (Si) a supply power of the RF generator (101) and determining an output power of the impedance matching circuit (102); - Adjusting (S2) the RF generator (101), in particular by changing the frequency of the RF generator (101) and / or the impedance matching circuit (102), so that an overall efficiency of the plasma process supply system (100), which results from the determined supply power of the RF generator (101) and the output power of the impedance matching circuit (102), is increased.

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