A control device for controlling a plasma process supply system, a plasma process supply system having such a control device, and a method for operating the control device.

Abstract

The present invention relates to a control device (1) used to control a plasma process supply system (100). The plasma process supply system comprises an RF generator (101) and an impedance matching circuit (102) used for connection to a load (103). The control device (1) is designed to determine the supply power of the RF generator (101) and the 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), specifically by changing the frequency of the RF generator (101), thereby increasing the overall efficiency of the plasma process supply system (100) obtained from the determined supply power of the RF generator (101) and the output power of the impedance matching circuit (102).

Description

Technical Field

[0001] The present invention relates to a control device for controlling a plasma process supply system, a plasma process supply system having such a control device, and a method for operating the control device.

[0002] Surface treatment of a workpiece using a plasma laser and a gas laser is, specifically, an industrial process in which plasma is generated using a direct current or a high-frequency alternating current signal having an operating frequency in the range of several tens of kHz to GHz, specifically up to 100 GHz, in a plasma chamber.

[0003] The plasma chamber is connected to a high-frequency generator (RF generator) via additional electronic components such as a coil, a capacitor, a cable, or a transformer. These additional components can be an oscillation circuit, a filter, or an impedance matching circuit.

[0004] In the plasma process, there is a problem that the electrical load impedance of the plasma chamber (plasma = consumption part) generated during the process depends on the conditions in the plasma chamber and can vary greatly. Specifically, the characteristics of the workpiece, the electrodes, and the gas conditions are taken into account.

[0005] The high-frequency generator has a limited operating range with respect to the impedance of the connected electrical load (= consumption part). If the load impedance deviates from the allowable range, the RF generator may be damaged or even destroyed.

[0006] Therefore, an impedance matching circuit (match box) is usually required to convert the impedance of the load to the nominal impedance of the generator output.

[0007] Various impedance matching circuits are known. An impedance matching circuit can be fixed and have a predetermined conversion effect; that is, an impedance matching circuit consists of electrical components that do not change during operation, specifically coils and capacitors. This is particularly useful for always consistent operation, such as with gas lasers. Furthermore, impedance matching circuits are known in which at least some of the components of the impedance matching circuit are mechanically variable. For example, a motor-driven rotary capacitor is known, whose capacitance can be changed by changing the arrangement of the capacitor plates relative to each other.

[0008] Plasma can be assigned to three impedance ranges in a general sense. Before ignition, a very high impedance exists. During normal operation, i.e., during the intended operation using the plasma, a lower impedance exists. In the case of undesirable local discharges (arcs) or plasma fluctuations, very low impedance may occur. In addition to these three specified impedance ranges, other special conditions with other associated impedance values ​​may arise. If the load impedance changes suddenly and the load impedance or converted load impedance falls outside the acceptable impedance range, the RF generator or the transmission equipment between the RF generator and the plasma chamber may be damaged. Undesirable plasma stabilization states also exist.

[0009] Impedance matching circuits are described, for example, in the document DE 10 2009 001 355 A1.

[0010] Plasma processes are also known to require a lot of energy, which plays an increasingly important role today. Losses specifically arise from high idle currents flowing through impedance matching circuits, reducing their efficiency. To transfer the desired power to the plasma, the high-frequency generator must therefore provide higher output power, which further increases power losses.

[0011] Object of the invention Therefore, the objective of the present invention is to establish a plasma process that is as energy-efficient as possible.

[0012] Summary of the Invention This objective is achieved by a control device for controlling the plasma process supply system described in claim 1, by the plasma process supply system described in claim 17, and by a method for operating the control device described in 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 present invention comprises an RF generator and an impedance matching circuit, and functions to control a plasma supply system used to connect to a load, specifically a plasma chamber. The control device is designed to determine the supply power of the RF generator and the output power of the impedance matching circuit. The term “supply power” specifically refers to the power required to operate the RF generator. This refers in particular to the power that at least one of the RF generator’s power sources receives from or delivers to the (public) power grid. If the RF generator has several power sources, “supply power” is the sum of the power that the RF generator’s power sources receive from or deliver to the (public) power grid. The term “output power” refers to the power derived from the power delivered by the RF generator and output by the impedance matching circuit. If multiple signals from different RF generators or DC generators are fed to the impedance matching circuit, the signals from the other RF generators or DC generators should be ignored when determining the output power. These other signals can be ignored in particular because they have different frequencies. Furthermore, the control device is designed to adjust the RF generator and / or impedance matching circuit, specifically by changing the frequency of the RF generator, thereby increasing the overall efficiency of the plasma process supply system, which is obtained from the determined supply power of the RF generator and the output power of the impedance matching circuit.

[0014] Here, it is particularly advantageous that the control unit is designed to adjust the RF generator and / or impedance matching circuit to optimize the overall efficiency. This means the control unit is designed to determine the overall efficiency based on the power supplied by the RF generator and the output power of the impedance matching circuit. The control unit therefore takes both the RF generator and the impedance matching circuit into consideration. This avoids individual optimization of either the RF generator or the impedance matching circuit. Studies have shown that even a reduction in the efficiency of the impedance matching circuit, as determined from its input and output power, can lead to an increase in overall efficiency if the RF generator or impedance matching circuit is adjusted accordingly. In other words, a reduction in the efficiency of one component (RF generator or impedance matching circuit) can be acceptable because it simultaneously leads to a significant increase in the efficiency of other components, resulting in an improvement in overall efficiency.

[0015] The control device is described in the prior art, specifically US10818477B2, US20210134563A1, and US20180053633A1.

[0016] In advantageous embodiments, the control device is designed to calculate the overall efficiency of the plasma process supply system based on the determined supply power and output power. Specifically, the output power is divided by the supply power. Before calculating the overall efficiency, it is conceivable to average multiple measurements of the supply power and output power.

[0017] In an advantageous embodiment, the control device is designed to determine the output power of the RF generator, specifically the forward power and the reflected power or quantities related to the reflected power.

[0018] In advantageous embodiments, the control device is designed to adjust, specifically, the output power of the RF generator. The control can be performed, for example, to minimize or lower the reflected power below a threshold.

[0019] In advantageous embodiments, the control device is designed to continuously change the frequency of the RF generator during operation. For example, frequency changes may occur more than 5, 10, 100, 200, 500, or 1000 times per second. The control device is further designed to continuously check whether the overall efficiency improves after the frequency change. This continuous check may occur, for example, more than 5, 10, 100, 200, 500, or 1000 times per second. Preferably, the continuous check is always performed after a frequency change, and more preferably, a waiting period is observed after the frequency change before checking the overall efficiency. This means that the overall operating efficiency can always be optimized. Changing the frequency of the RF generator is also very easy and very 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 element used. This ensures that the RF generator is not operated outside of its specifications, which could, for example, lead to damage to the RF generator itself.

[0020] In advantageous embodiments, the control device is designed to further change the frequency in the same direction if the overall efficiency improves. For example, if the frequency is increased and the overall efficiency improves, the frequency is further increased in a subsequent step. Additionally or alternatively, the control device is designed to change the frequency in the opposite direction if the overall efficiency decreases. For example, if the frequency is increased and the overall efficiency deteriorates as a result, the frequency is reduced in the next step.

[0021] In an advantageous embodiment, the control device is designed to select a step size for changing the frequency of the signal output by the RF generator to the impedance matching circuit in response to a change in overall efficiency. Preferably, a larger step size results in a larger change in overall efficiency, which causes the system to fluctuate rapidly.

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

[0023] In an advantageous embodiment, the control device comprises a factory-trained AI module to adjust an RF generator and / or an impedance matching circuit, specifically to vary the frequency of the RF generator, based at least on the supply power and output power. During training, the AI ​​module is supplied with different values ​​of the supply power of the RF generator and the output power of the impedance matching circuit. Simultaneously, the AI ​​module is informed of the frequency at which the RF generator should operate, or whether the frequency at which the RF generator should operate should be increased, decreased, or remain the same. Additionally or alternatively, the AI ​​module may also be informed of how the impedance matching circuit should be configured, specifically how the conversion ratio should be selected. The entire procedure can also be made dependent on the current plasma process. During operation, the AI ​​module is supplied with the supply power of the RF generator and the output power of the impedance matching circuit. This occurs at the input node. At the input node, each type of plasma process can be supplied to the AI ​​module. The AI ​​module comprises a plurality of intermediate nodes and at least one output node that can output information regarding the frequency to be set for the RF generator, or whether the frequency should be increased or decreased. Additionally or alternatively, information regarding the conversion ratio of the impedance matching circuit, or whether the conversion ratio should be increased or decreased, can be output to at least one output node.

[0024] 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. Here, "exceeds" means both a transition from a larger value to a smaller value, or a transition from a smaller value to a larger value. This prevents the frequency from constantly changing. Additionally or alternatively, this can also be applied to changes in the conversion ratio of the impedance matching circuit. For example, if the overall efficiency exceeds 70%, there is no need to change the frequency of the RF generator and / or the conversion ratio of the impedance matching circuit.

[0025] In an advantageous embodiment, the control device is designed to control the impedance matching circuit so that the conversion ratio between the input impedance of the impedance matching circuit and the output impedance of the impedance matching circuit can change during operation, and the control device is further designed to check whether the overall efficiency improves after the change in the conversion ratio. The input impedance and / or output impedance of the impedance matching circuit can change during the process, however this is not necessarily required.

[0026] In advantageous embodiments, the control device is designed to control the impedance matching circuit so that the input impedance and / or output impedance do not change when the conversion ratio is changed. For this purpose, the impedance matching circuit preferably comprises at least one conversion stage, so that the input impedance is converted to at least one first intermediate impedance, and then to the output impedance. The input impedance can still correspond to the nominal impedance of an RF generator, such as 50 ohms, and the output impedance can still correspond to the plasma impedance. The overall efficiency can be further increased by changing the conversion ratio from the input impedance to at least one first intermediate impedance.

[0027] In an advantageous embodiment, the impedance matching circuit comprises a first conversion stage designed to convert an input impedance into a first intermediate impedance. The impedance matching circuit may comprise a second conversion stage designed to convert the first intermediate impedance into a second intermediate impedance. The impedance matching circuit may comprise a third conversion stage designed to convert the second intermediate impedance into an output impedance. The control device is designed to control the impedance matching circuit such that, for a given input impedance and output impedance, the conversion path of the first conversion stage and / or the second conversion stage and / or the third conversion stage changes, and in this case the control device re-determines the overall efficiency of the plasma process supply system after such a change.

[0028] In an advantageous embodiment, the supplied power is active power. Additionally or alternatively, the output power is active power.

[0029] In an advantageous embodiment, the control device comprises a first measurement unit. The first measurement unit is designed to determine the supplied power from the alternating voltage and alternating current present at the input of the power supply unit of the RF generator, which can be obtained from the (common) power grid. In this case, the overall efficiency also includes the efficiency of at least one power supply of the RF generator. Alternatively, the first measurement unit is present at the output of the power supply of the RF generator and is designed to determine the supplied power from the direct voltage and direct current that functions to supply at least one RF amplifier of the RF generator. In this case, the supplied power can be determined more easily. At least one power supply unit is specifically designed to convert a main supply voltage having a frequency of, for example, 50 Hz or 60 Hz into a regulated direct voltage, which can also be referred to as an intermediate circuit voltage. This direct voltage is then fed to at least one RF amplifier, which converts the direct voltage into RF power in order to amplify the RF signal.

[0030] In an advantageous embodiment, the control device comprises at least a 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.

[0031] 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 designed to determine the output power based on the conversion ratio of the impedance matching circuit.

[0032] In an advantageous embodiment, the voltage sensor of the second measuring unit is a capacitive voltage divider, and the first capacitance is formed by a conductive ring or cylinder through which a cable for carrying RF power can be routed. In addition, the current sensor of the second measuring unit is a coil arranged around the conductive ring or cylinder. This design enables non-contact measurement of current and voltage.

[0033] In an advantageous embodiment, the control device is specifically designed to determine the reflectance at the output of the RF generator. The control device is designed to adjust the RF generator and / or the impedance matching circuit, specifically to change the frequency of the RF generator. Therefore, the reflectance is reduced, and the control device is further designed to adjust the RF generator and / or the impedance matching circuit such that the reflectance increases when the overall efficiency is improved simultaneously. Particularly advantageously, an increase in reflectance is also allowed when the overall efficiency is improved simultaneously.

[0034] The plasma process supply system according to the present invention comprises the control device described above. The plasma supply system comprises 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 via a second cable connection, specifically in the form of a plasma chamber. It is particularly advantageous that the control device acts as a kind of central control device and controls both the RF generator and the impedance matching circuit.

[0035] In an advantageous embodiment of the plasma process supply system, the RF generator comprises at least one power supply and at least one RF amplifier. The at least one power supply comprises an input for connection to the (public) power grid and an output for connection to at least one RF amplifier. The at least one power supply is designed to convert an AC voltage at the input to a (adjustable) DC voltage, to output the DC voltage at the output, and to supply the DC voltage to at least one RF amplifier. A control device is designed to determine the power supplied at the input, or at the output, or between the input and output.

[0036] In an advantageous embodiment of a plasma process supply system, the impedance matching circuit comprises at least one adjustable reactance to vary the impedance conversion ratio between an input section to which an RF generator is connected and an output section to which a load can be connected. The reactance is mechanically adjustable and / or electrically adjustable and, specifically, is formed 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 capacitance, its level can be varied, for example, by motor-driven adjustment of the plate spacing. The term “adjustable” can also be understood as switching the reactance on and / or off.

[0037] The method according to the present invention functions to operate the control device mentioned at the beginning for controlling a plasma supply system having an RF generator and an impedance matching circuit. In the first step, the supply power of the RF generator is determined. Furthermore, the output power of the impedance matching circuit is determined. In the second process step, the RF generator is adjusted, specifically by changing the frequency of the RF generator. Additionally or alternatively, the impedance matching circuit is adjusted. This results in an increase in the overall efficiency of the plasma process supply system obtained from the determined supply power of the RF generator and the output power of the impedance matching circuit.

[0038] The present invention is described below purely by example with reference to the drawings. [Brief explanation of the drawing]

[0039] [Figure 1] An exemplary embodiment of a plasma process supply system according to the present invention, having a control device according to the present invention, is shown. [Figure 2] Figures 2A and 2B show various exemplary embodiments of how impedance matching circuits can be constructed. [Figure 3] An exemplary embodiment is shown of how the measuring unit can be configured to measure current and voltage. [Figure 4] An exemplary embodiment is shown of how the measuring unit can be configured to measure current and voltage. [Figure 5] An exemplary embodiment of an exemplary efficiency curve is shown. [Figure 6] A flowchart illustrating the operation of the control device is shown.

[0040] Figure 1 shows a plasma process supply system 100 comprising a control device 1. The plasma generation system 100 further comprises an RF generator 101, an impedance matching circuit 102, and specifically, at least one consumption unit 103 in the form of a plasma chamber. The RF generator 101 has a nominal power P Nominal The RF generator 101 is designed to supply an RF signal, specifically in the form of a CW signal, having a frequency f0, and to output it at output terminal 101a. The impedance matching circuit 102 includes an input terminal 102a, and the RF generator 101 is connected to the input terminal 102a via a first cable connection 104a. The impedance matching circuit 102 further includes an output terminal 102b. The output terminal 102b is connected to at least one consumer unit 103 via a second cable connection 104b. The first cable connection 104a and / or the second cable connection 104b may include, for example, one or more cables connected in series and / or in parallel. Preferably, coaxial cables are used.

[0041] The consumption unit 103, i.e., the plasma chamber, comprises at least one electrode 105 for generating plasma 106. The electrode 105 is (galvanically) connected to the output terminal 102b of the impedance matching circuit 102. In this embodiment, a camera system 107, designed to monitor the plasma 106, is located inside the plasma chamber.

[0042] The control device 1 is preferably a processor and / or FPGA and / or microcontroller and / or ASIC. The control device 1 may also include a storage unit.

[0043] The control device 1 is designed to control the RF generator 101, specifically by activating or deactivating 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 of the RF signal (the type of RF signal, the modulation of the RF signal) by appropriately controlling the RF generator 101.

[0044] The RF generator 101 includes a power supply 109 designed to convert alternating current to (regulated) direct current and alternating voltage to (regulated) direct voltage. The RF generator 101 also includes a signal generator 110 and an RF amplifier 111. The signal generator 110 is specifically designed to generate a 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 transmit it to the impedance matching circuit 102 via output terminal 101a. The RF amplifier 111 is powered by the power supply 109.

[0045] The control device 1 is also preferably designed to control the impedance matching circuit 102. Specifically, the control device 1 is designed to change the conversion ratio within the impedance matching circuit 102.

[0046] The control device 1 also includes a first measurement unit 2. The first measurement unit 2 is designed to determine the power supplied from the AC voltage and AC current drawn by the power supply unit 109 of the RF generator 101 from the (public) power grid. Alternatively, the first measurement unit 2 is designed to determine the power supplied from the DC voltage and DC current provided at the output of the power supply 109 of the RF generator 101 and used to supply at least one RF amplifier 111. The first measurement unit 2 may include, for example, a shunt resistor for measuring DC current and, for example, a voltage divider for measuring DC voltage.

[0047] The control device 1 also includes a second measurement unit 3. The second measurement unit 3 includes at least one directional coupler or current sensor 5 and a voltage sensor 6. Designs having the current sensor 5 and voltage sensor 6 are shown in Figures 3 and 4. The control device 1 is designed to determine, specifically calculate, the output power at the output section of the impedance matching circuit 102 based on the measurement results of at least one directional coupler or current sensor 5 and voltage sensor 6. In Figure 1, the second measurement unit 3 is located at the output section of the impedance matching circuit 102. The second measurement unit 3 can also be located at the input section of the impedance matching circuit 102, in which case the control device 1 is designed to determine the output power at the output terminal 102b of the impedance matching circuit 102 based on the conversion ratio of the impedance matching circuit 102.

[0048] The supplied power is preferably active power. Similarly, the output power is also preferably active power.

[0049] As described, the control device 1 is designed to determine, specifically measure, the supply power of the RF generator 101 and the output power of the impedance matching circuit 102. In this case, the control device 1 is designed to adjust the RF generator 101 and / or the impedance matching circuit 102, specifically by changing the frequency of the RF generator 101, thereby increasing the overall efficiency of the plasma process supply system 100 obtained from the determined supply power of the RF generator 101 and the output power of the impedance matching circuit 102.

[0050] The plasma generation system 100 also preferably comprises an operating unit 108. The operating unit 108 is preferably a screen, specifically a touch-sensitive screen. In addition to the screen, the operating unit 108 may also include input means such as a keyboard and / or mouse. The operating unit 108 may also be a web server that provides data and receives user input. The control unit 1 is designed to display the current settings of the RF generator 101 and / or impedance matching circuit 1 on the operating unit 108.

[0051] The control device 1 can also be designed to display on the operating unit 108 the measured values ​​received by the first measuring unit 2 and / or the second measuring unit 3, for example, the supplied power or the output power. The determined overall efficiency can also be displayed on the operating unit 108 by the control device 1. Preferably, the control device 1 is designed to receive from the operating unit 108, for example, the power of the RF signal, the frequency of the RF signal, and / or the setpoint specifications of the RF signal waveform, and to generate and transmit the corresponding activation variables of the RF generator 101.

[0052] The control device 1 can be designed to continuously change the frequency of the RF generator 101 during operation. The control device 1 can also be further designed to continuously check whether the overall efficiency improves after the frequency change.

[0053] The control device 1 can be designed to further change the frequency of the RF generator 101 in the same direction as the previous frequency change if the overall efficiency has improved since the previous frequency change. Otherwise, the control device 1 can be designed to change the frequency in the opposite direction.

[0054] The control device 1 can also be designed to select the step size for changing the frequency of the RF generator 101 in response to changes in overall efficiency. If the overall efficiency increases significantly (above the first threshold) after a frequency change, the step size for the next frequency change can be increased. If the overall efficiency does not increase much after a frequency change (below the second or first threshold), the step size for the next frequency change can be selected to be smaller.

[0055] In principle, it can be assumed that the control device 1 is designed only to set frequencies within a specific frequency range. Such validation checks may be performed additionally or alternatively by the RF generator 101.

[0056] The control device 1 can also be designed to implement control to increase the overall efficiency only when the overall efficiency falls below a certain level.

[0057] In Figure 1, the control unit 1 also includes an AI module 4. The AI ​​module 4 is factory-trained to adjust the RF generator 101 and / or impedance matching circuit 102 based at least on the supply power and output power, and optionally on the plasma process, to increase overall efficiency. However, the use of the AI ​​module 4 is optional.

[0058] The impedance matching circuit 102 is also designed to convert the input impedance at its input terminal 102a to the output impedance at its output terminal 102b. For this purpose, the impedance matching circuit 102 preferably comprises at least a first conversion stage 112a. In the exemplary embodiment shown in Figure 1, the impedance matching circuit 102 comprises a first conversion stage 112a, a second conversion stage 112b, and a third conversion stage 112c. The first conversion stage 112a is designed to convert the input impedance to a first intermediate impedance. The second conversion stage 112b is designed to convert the first intermediate impedance to a second intermediate impedance. The third conversion stage 112c is designed to convert the second intermediate impedance to an output impedance. The control device 1 is designed to control the impedance matching circuit 112a such that the conversion paths of the first conversion stage 102a and / or the second conversion stage 112b and / or the third conversion stage 112c change for predetermined input and output impedances, and in this case, the control device 1 re-evaluates the overall efficiency of the plasma process supply system after such changes. Preferably, the input and output impedances remain unchanged. Only the conversion paths 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 change. The impedance values ​​of the first and second intermediate impedances can be changed.

[0059] Figures 2 and 3 illustrate various embodiments of the impedance matching circuit 102. The impedance matching circuit 102 may include exactly one conversion stage 112a, which can be constructed according to the embodiments shown in Figures 2A and 2B. If the impedance matching circuit 102 includes multiple conversion stages 112a, 112b, and 112c, each conversion stage 112a, 112b, and 112c can be constructed according to the exemplary embodiments shown in Figures 2A and 2B. It will also be understood that the impedance matching circuit 102 may be configured differently from those shown in Figures 2A and 2B.

[0060] In Figure 2A, the input terminal 102a of the impedance matching circuit 102 is connected to a first coil 113 (first inductance) and a second coil 114 (second inductance). The first coil 113 and the second coil 114 are connected to a common node at their first terminals, thereby connecting to the input terminal 102a of the impedance matching circuit 102. The first coil 113 is connected to 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 capacitor 115 and / or the second capacitor 116 are specifically adjustable components in the form of rotary capacitors, whose capacitance can be changed via a stepping motor. Alternatively, solid switches can be used to add and remove capacitance as quickly as possible. Specifically, the plate spacing of the first capacitor 115 and the second capacitor 116 can be changed. The control device 1 is designed to control each stepper motor accordingly. The capacitances of the first capacitor 115 and the second capacitor 116 can be adjusted independently of each other. Preferably, the impedance matching circuit 102 does not include any additional components. Naturally, the positions of the first coil 113 and the first capacitor 115 can also be swapped. In this case, the first capacitor 115 is located at the input terminal 102a of the impedance matching circuit 102, and the first coil 113 is located at the reference ground. Additionally or alternatively, the positions of the second coil 114 and the second capacitor 116 can also be swapped. In this case, the second capacitor 116 is located at the input terminal 102a of the impedance matching circuit 102, and the second coil 114 is located at the output terminal 102b of the impedance matching circuit 102.

[0061] The input terminal 102a of the impedance matching circuit 102 is connected to the first capacitor 115 (first capacitance) in Figure 2B. The first capacitor 115 is connected to both the first coil 113 (first inductance) and the second coil 114 (second inductance). This is done via a common node to which both the first capacitor 115 and the first and second coils 113 and 114 are connected. The first coil 113 is still connected to the reference ground. The second coil 114 is connected (in series) to the second capacitor 116 (second capacitance). The second capacitor 116 is connected to the output terminal 102b of the impedance matching circuit 102. The positions of the second coil 114 and the second capacitor 116 can also be reversed. In this case, the second capacitor 116 is connected to the common node and the second coil 114 is connected to the output terminal 102b of the impedance matching circuit 102. Preferably, the impedance matching circuit 102 does not include any additional components.

[0062] Figures 3 and 4 show exemplary embodiments of possible structures of the second measurement unit 3. In principle, the first measurement unit 2 can be constructed identically to or similarly to the second measurement unit 3. In this exemplary embodiment, the second measurement unit 3 is designed to measure voltage and current non-contact.

[0063] For this purpose, the second measurement unit 3 includes a current sensor 5 and a voltage sensor 6.

[0064] However, it is still preferable to measure the phase relationship between current and voltage so that the impedance can be calculated.

[0065] The current sensor 5 of the second measuring unit 3 is specifically a coil in the form of a Rogowski coil. The ends of the coil are preferably connected to each other via a shunt resistor 7. The voltage drop across the ends of the shunt resistor 7 can be digitized by the first A / D converter 8.

[0066] The voltage sensor 6 of the second measurement unit 3 is preferably incorporated as a capacitive voltage divider. The first capacitor 9 is formed by a conductive ring 9. A conductive cylinder can also be used. The corresponding first cable connector 104a and second cable connector 104b are guided through this conductive ring 9. The second capacitor 10 of the voltage sensor 6, which is constructed as a voltage divider, is connected to reference ground. The 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.

[0067] In principle, the second measuring unit 3 can be placed on or incorporated into a (common) circuit board. The first capacitor 9 can be formed by coatings on a first side and a second side of the circuit board. In this case, the coatings on the first and second sides are electrically connected to each other by vias. The first cable connection 104a and the second cable connection 104b pass through openings in the circuit board. The second capacitor 10 can be formed by discrete components.

[0068] The current sensor 5, in the form of a coil, specifically in the form of a Rogowski coil, is further spaced from the first cable connection 104a or the second cable connection 104b than the first capacitor 9. The coil can also be formed on the same circuit board by corresponding coatings and vias. The coil for current measurement and the first capacitor for voltage measurement preferably extend through a common plane.

[0069] The shunt resistor 7 can also be placed on this circuit board. The same applies to the first A / D converter 8 and / or the second A / D converter 11.

[0070] The first measuring unit 2 and / or the second measuring unit 3 can also be designed as directional couplers.

[0071] Figure 5 shows, as an example, the time evolution of several signals of such a plasma process supply system 100 in operation. In the upper graph, the evolution of reflectance Pr / Pi is shown by curve 16 over time t. The lower graph shows the simultaneous evolution of different efficiencies η over time t. The first curve 18 can represent, for example, the efficiency curve of the impedance matching circuit 102. The second curve 19 can represent, for example, the efficiency evolution of the RF generator. The third curve 20 can represent, for example, the overall efficiency evolution of the plasma process supply system. The reflectance moves from an initial value close to 30% to a value close to 0% at time t1. This can represent, for example, the evolution of events when the plasma process supply system 100 is switched on. At time t2, the reflectance increases slightly again, and at time t3, the reflectance increases slightly further and remains constant, but is greater than 0% from time t4 onward. Such behavior of the reflectance is usually undesirable. According to previous rules, it is desirable that the reflectance remain as close to 0% as possible throughout the entire operating time, such as between times t1 and t2. However, according to the present invention, different values ​​are preferred in the control, as will be explained again below.

[0072] Between the start and time t1, the efficiency of the impedance matching circuit 102 and the RF generator 101 changes, thereby changing the overall efficiency of the plasma process supply system 100.

[0073] At time t2, the efficiency of the RF generator 101 begins to increase further by changing the settings of the RF generator 101 and / or the impedance matching circuit 102, specifically by changing the frequency of the RF generator 101. At the same time, the efficiency of the impedance matching circuit 102 remains constant. This is not necessarily required, but is presented here for clarity. This further increases the overall efficiency. At the same time, a slight increase in reflectivity is permissible. The trigger for this setting is the control device 1, which controls the RF generator 101 and / or the impedance matching circuit 102 accordingly.

[0074] At time t3, the efficiency of the impedance matching circuit begins to increase further by changing the settings of the RF generator 101 and / or the impedance matching circuit 102, specifically by changing the frequency of the RF generator 101. At the same time, the efficiency of the RF generator 101 remains constant. This is not necessarily required, but is presented here for clarity. As a result, the overall efficiency increases further. At the same time, a slight increase in reflectivity is permitted again. The trigger for this further adjustment is again the control device 1, which controls the RF generator 101 and / or the impedance matching circuit 102 accordingly.

[0075] Beyond time t4, no further increase in overall efficiency can be achieved. At this point, it is not possible to further improve reflectivity without again worsening overall efficiency. Therefore, this setting is maintained.

[0076] In another exemplary embodiment, the reflectivity may be close to or equal to zero during the time interval between t3 and t4, which is the time range in which the overall efficiency of the plasma process supply system is maximized.

[0077] Figure 6 illustrates a method according to the present invention for operating a control device 1 for controlling a plasma process supply system 100. In a first process step S1, the supply power of the RF generator 101 and the output power of the impedance matching circuit 102 are determined. In a second process step S2, the RF generator 101 is adjusted, specifically by changing the frequency of the RF generator 101 and / or the impedance matching circuit 102, thereby increasing the overall efficiency of the plasma process supply system 100, which is obtained from the determined supply power of the RF generator 101 and the output power of the impedance matching circuit 102.

[0078] The present invention is not limited to the exemplary embodiments described. Within the scope of the invention, all described and / or depicted characteristics can be freely combined with one another.

Claims

1. A control device (1) for controlling a plasma process supply system (100) having an RF generator (101) and an impedance matching circuit (101) for connection to a load (103), wherein the control device (1) has the following characteristics: - The control device (1) is designed to determine the power supplied by the RF generator (101) and the 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), specifically by changing the frequency of the RF generator (101), thereby increasing the overall efficiency of the plasma process supply system (100) obtained from the determined supply power of the RF generator (101) and the output power of the impedance matching circuit (102), the control device (1).

2. The following characteristics: - The control device (1) according to claim 1, characterized in that 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 output power.

3. The following characteristics: - The control device (1) according to claim 1 or 2, characterized in that the control device (1) is designed to specifically and continuously change the frequency of the RF generator (101) during operation, and the control device (1) is further designed to specifically and continuously check whether the overall efficiency improves after the frequency change.

4. The following characteristics: - The control device (1) is designed to further change the frequency in the same direction when the overall efficiency is improved, and / or - The control device (1) according to claim 3, characterized in that the control device (1) is designed to change the frequency in the opposite direction when the overall efficiency decreases.

5. The following characteristics: - The control device (1) according to claim 3 or 4, characterized in that the control device (1) is designed to select a step size for changing the frequency depending on the change in the overall efficiency.

6. The following characteristics: - The control device (1) according to any one of claims 3 to 5, characterized in that the control device (1) is designed to set the frequency only within a specific frequency range.

7. The following characteristics: - The control device (1) according to any one of claims 3 to 6, further comprising an AI module (4) which is factory-trained to adjust the RF generator (101) and / or the impedance matching circuit (102) based on at least the supply power and the output power, specifically to change the frequency of the RF generator (101).

8. The following characteristics: - The control device (1) according to any one of claims 3 to 7, characterized in that the control device (1) is designed to change the frequency of the RF generator (101) only when the overall efficiency exceeds a threshold.

9. The following characteristics: - The control device (1) according to any one of claims 1 to 8, characterized in that the control device (1) is designed to control the impedance matching circuit (102) such that the conversion ratio between the input impedance of the impedance matching circuit (102) and the output impedance of the impedance matching circuit (102) can be changed during operation, and the control device (1) is further designed to check whether the overall efficiency is improved after the change in the conversion ratio.

10. The following characteristics: The control device (1) according to claim 9, characterized in that the control device (1) is designed to control the impedance matching circuit (102) such that the input impedance and / or output impedance remain unchanged when the conversion ratio changes.

11. The following characteristics: - A control device (1) according to any one of claims 1 to 10, characterized in that the supplied power is active power and / or the output power is active power.

12. The following characteristics: - The control device (1) includes a first measuring unit (2), - The first measurement unit (2) is designed to determine the power supply from AC voltage and AC current that can be obtained from the power grid and are present at the input of the power supply unit (109) of the RF generator (101), or The control device (1) according to any one of claims 1 to 11, characterized in that the first measuring unit (2) is located at the output section of the power supply unit (109) of the RF generator (101) and is designed to determine the supplied power from a DC voltage and a DC current that functions to supply to at least one RF amplifier (111) of the RF generator (101).

13. The following characteristics: - The control device (1) includes a second measuring unit (3), - The second measuring unit (3) comprises at least one directional coupler or current sensor (5) and voltage sensor (6), - The control device (1) according to any one of claims 1 to 12, characterized in that the control device (1) is designed to determine the output power based on the measurement results of at least one directional coupler or the current sensor (5) and the voltage sensor (6).

14. The following characteristics: - The second measurement unit (3) can be placed at the output of the impedance matching circuit (102), or - The control device (1) according to claim 13, characterized in that the second measurement unit (3) can be placed at the input of the impedance matching circuit (102), and the control device (1) is designed to determine the output power based on the conversion ratio of the impedance matching circuit (102).

15. The following characteristics: - The voltage sensor (6) of the second measuring unit (2) is a capacitive voltage divider, and the first capacitance (9) is formed by a conductive ring or cylinder through which a cable (104b) for transporting RF power can be routed. - The control device (1) according to claim 13 or 14, characterized in that the current sensor (5) of the second measuring unit (3) is a coil arranged around the conductive ring (6) or cylinder.

16. The following characteristics: - Specifically, the control device (1) is designed to determine the reflectance at the output section of the RF generator (101). - The control device (1) according to any one of claims 1 to 15, characterized in that the control device (1) is designed to adjust the RF generator (101) and / or the impedance matching circuit (102) so that the reflectance is reduced, specifically by changing the frequency of the RF generator (101), and further designed to adjust the RF generator (101) and / or the impedance matching circuit (102) so that the reflectance is increased when the overall efficiency is simultaneously improved.

17. A plasma process supply system (100) having a control device (1) according to any one of claims 1 to 16, wherein the following characteristics: - The plasma process supply system (100) includes an RF generator (101) and an impedance matching circuit (102), - Preferably, the RF generator (101) is connected to the impedance matching circuit (102) via the first cable connection (104a). - A plasma process supply system (100) characterized in that the impedance matching circuit (102) can be connected to a load (103) via a second cable connection (104b), specifically in the form of a plasma chamber.

18. The following characteristics: - The RF generator (101) comprises at least one power supply (109) and at least one RF amplifier (111). - The at least one power supply (109) comprises an input section for connecting to the power supply and an output section for connecting to the at least one RF amplifier (111), - The at least one power supply (109) is designed to convert the AC voltage at the input section into a DC voltage, to output the DC voltage at the output section, and to supply the DC voltage to the at least one RF amplifier (111). - The plasma process supply system (100) according to claim 17, characterized in that the control device (1) is designed to determine the supplied power in the input unit, or in the output unit, or between the input unit and the output unit.

19. The following characteristics: - The impedance matching circuit (102) includes at least one adjustable reactance to change the impedance conversion ratio between the input section to which the RF generator (101) is connected and the output section to which the load (103) can be connected. - The plasma process supply system (100) according to claim 17 or 18, characterized in that the reactance is mechanically adjustable and / or electrically adjustable and, specifically, is formed by at least one varactor and / or at least one switchable inductance and / or capacitance (115, 116), and / or at least one PIN diode.

20. A method for operating a control device (1) according to any one of claims 1 to 16, specifically for controlling a plasma process supply system (100) according to any one of claims 17 to 19, which has an RF generator (101) and an impedance matching circuit (102) for connection to a load (103), the method comprising the following steps: - Determine the power supply of the RF generator (101) (S １ ), and determining the output power of the impedance matching circuit (102), - Specifically, setting the RF generator (101) by changing the frequency of the RF generator (101) and / or the impedance matching circuit (102) so as to increase the overall efficiency of the plasma process supply system (100) obtained from the determined supply power of the RF generator (101) and the output power of the impedance matching circuit (102) (S ２ Methods including )

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