METHOD FOR IMPEDANCE MATCHING, IMPEDANCE MATCHING DEVICE, AND PLASMA SYSTEM

Abstract

The present invention relates to a method for impedance matching by means of an impedance matching network (2), the impedance matching network (2) having an input (3) for connection to an RF power generator (5) and an output (4) for connection to a load (6), the impedance matching network (2) having at least one first matching stage (10) each with one variable reactance (XP, XS) and a second matching stage (12) connected in series, the method comprising: a) adjusting the input impedance (Z in ), and b) measuring the measured input impedance (Z in ) and at least one current state value of at least one of the matching stages to obtain an intermediate impedance (Z inter ) and c) determining the intermediate impedance (Z inter ), determining a change target value (dXP,dXS) for at least one reactance (XP,XS) of one matching stage (10,12) from the impedance matching network (2) and a model of the impedance matching network (2); d) changing a state of at least one of the matching stages (10,12) based on the change target value (dXP,dXS); and e) repeating steps a) to d).

Description

[Technical Field]

[0001] The present invention relates to a method for impedance matching using an impedance matching network, the impedance matching network having an input for connecting to an RF power generator and an output for connecting to a load, the impedance matching network having at least one first matching stage, each with a variable reactance, and a second matching stage connected in series. The present invention also relates to an impedance matching device, a computer program product, and a non-volatile storage medium. The present invention also relates to a plasma system including such an impedance matching device or such an impedance matching network.

[0002] The load in this specification may refer to a plasma processing apparatus, particularly an RF-excited plasma processing apparatus, i.e., an apparatus for performing plasma processing. Impedance matching networks are often used in RF-excited plasma processing. An apparatus designed for impedance matching and / or having such an impedance matching network and a plasma processing apparatus connected to such an impedance matching network is hereinafter referred to as a plasma system. The frequency in this case is typically 1 MHz or higher, particularly in the range of 1 MHz to 200 MHz. RF-excited plasma processing is used, for example, to coat (sputter) and / or etch substrates in the manufacture of architectural glass, semiconductors, photovoltaics, flat screens, displays, etc. The impedance of such processes often changes very quickly, so impedance matching often needs to be performed very quickly (within a few milliseconds or less). The power typically supplied for such processes is several hundred watts, e.g., 300 W or more, but it is not uncommon for it to be 1 kilowatt or more, and often 10 kW or more. At such power levels, the voltages inside the impedance matching devices are often several hundred volts, e.g., 300 volts or more, but often 1000 volts or more. The currents in such circuits can be several amperes, often 10 amps or more, and sometimes even 100 amps or more. Realizing an impedance matching network at such voltages and currents has always been a major challenge. Being able to rapidly vary the reactance in such an impedance matching network is an even greater challenge.Examples of such impedance matching networks are disclosed in DE 102015220847 A1, DE 102011076404 A1, DE 102009001355 A1, DE 102011007598 A1, DE 102011007597 A1, DE 102014209469 A1, DE 202021100710 A1 or DE 202020103539 A1.

[0003] An impedance matching network is essentially used to match the impedance of a load to the impedance of a power generator. Typically, an impedance matching network is used to transform the load impedance to 50 ohms. The impedance matching network can have one or more variable reactances, such as capacitors, in an L-type configuration. The capacitance of the capacitor can be varied by a motor-type drive. A measuring device can identify the input impedance of the impedance matching network. A matching algorithm attempts to find the correct motor or switch position or other control means to achieve the impedance match.

[0004] Impedance matching using an impedance matching network often proves difficult when the load has a varying impedance, especially a rapidly varying load. It is known to use closed-loop control of the magnitude and phase of the input impedance to find the target position of the driver for a capacitor. However, both of these quantities depend on the capacitance value of the capacitor. This can result in slow closed-loop control. Sign changes in the impedance can cause instability, as can changes in the sign of the relationships dPhase / dC, d|(Z)| / dC, dRe(Z) / dC, or dIm(Z) / dC for two capacitors. Here, C is the capacitance, Z is the impedance, Re() is the real part, Im() is the imaginary part, and |()| is the magnitude of the complex variable in parentheses.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for impedance matching that allows impedance matching to be performed quickly and reliably.

[0006] According to the present invention, the above object is achieved by a method for impedance matching by means of an impedance matching network, the impedance matching network having an input for connection to an RF power generator and an output for connection to a load, in particular to an RF excited plasma processing device, the impedance matching network having at least one first matching stage each with a variable reactance and a second matching stage connected in series, the method comprising: a.) Input impedance Z in measuring b.) The measured input impedance Z in and at least one current state value of at least one of the matching stages to obtain an intermediate impedance Z inter wherein the intermediate impedance is in particular the impedance occurring between the matching stages; c.) Intermediate impedance Zinter and a model of the impedance matching network, determining a target change value for at least one reactance of one matching stage; d.) changing the state of at least one of the matching stages based on the change target value; e.) Repeat steps a.) to d.) The problem is solved by a method comprising:

[0007] The variable reactance can be configured as an inductance and / or a capacitance. Capacitance is preferred because it is simple to manufacture and operate. For example, the matching stage can have a series circuit of an inductance and a capacitance. In that case, the matching stage acts both capacitively and inductively.

[0008] Input impedance Z in Measuring may mean that the impedance at the input of the impedance matching network is measured. The impedance can be detected according to magnitude and phase and / or according to real and imaginary parts.

[0009] Input impedance Z in Measuring the reflection coefficient means measuring Z in It can also mean that is derived.

[0010] The intermediate impedance is the impedance measured at a matching stage located upstream of the output of the impedance matching network. The intermediate impedance can also be detected or determined according to magnitude and phase, and / or according to real and imaginary parts.

[0011] The model of the impedance matching network should also be understood to be a model for each of the matching stages, since the models of the matching stages are each part of the model of the impedance matching network.

[0012] In this way, faster and more robust closed-loop control of mechanical and / or electronic impedance matching networks can be achieved. Known algorithms often fail to converge, i.e., do not reach the desired point, or are unable to fully utilize the mechanical dynamics of the drive being used.

[0013] The above steps a.) to d.) can be repeated until the input impedance is above or below a predetermined value. It has been found that the method according to the present invention requires significantly fewer iterations than conventional methods. This allows for much faster impedance matching.

[0014] The state value can be the position of a mechanically variable reactance or the switching state of an electronically variable reactance, for example the position of a driver of a mechanically variable capacitance.

[0015] The intermediate impedance can be determined depending on the state based on a correspondence between the intermediate impedance and the input impedance. This correspondence can be determined depending on the detected state during calibration. In particular, a lookup table for each matching stage can be created during calibration in this way. Preferably, the calibration and creation of the lookup table for each matching stage are performed independently of each other matching stage.

[0016] The target value of change is the intermediate impedance target value Z intersoll It has been found to be advantageous to determine the value based on Z. To compensate for variability or inaccuracy in the look-up table, it is advantageous to perform a relative calculation. For example, Z interis j40 ohms, and the intermediate impedance target value is identified as j45 ohms, then the value that will result in j5 ohms or greater can be retrieved from the current entries in the lookup table. This is then the target position or change target, which has the advantage of compensating for offset errors and reducing scaling errors as one gets closer to the desired match.

[0017] The input impedance measurement is several orders of magnitude faster than the motor speed of the capacitor driver in the case of a mechanical impedance matching network. The determination of the mid-point impedance is not precise due to various errors (model, measurement, variable plasma impedance). However, the determination of the mid-point impedance specifies the approximate target position of the driver at the start. This allows for maximum acceleration of the impedance matching. While varying the reactance, Z in and Z inter The identification of Z intersoll is corrected.

[0018] The intermediate impedance target value is determined based on at least one predetermined boundary condition, e.g., Z in The real part of the impedance can be specified based on 50 ohms. Such a boundary condition makes it easy to specify the intermediate impedance target value.

[0019] The state of at least one of the matching stages can be changed by a target change amount or in the direction of the target change amount. As mentioned above, it is advantageous to perform relative matching. That is, it is not necessary to specify an absolute value for the changed state. It is sufficient to specify how much the state of one matching stage must be changed so that the state of the other matching stage can be changed so that matching is performed. This is performed using an intermediate impedance.

[0020] The states of the two matching stages can be changed simultaneously, which accelerates impedance matching.

[0021] A circuit model can be used as a model for the impedance matching network, which has particular advantages when the impedance matching network is simply constructed, for example, when it has an L-type configuration.

[0022] Alternatively, the impedance matching network may be modeled using a transmission parameter model, a scattering parameter model, or a parameter model that can be derived from the transmission parameter model or the scattering parameter model. For example, Z, Y, M, and X parameters can be determined from the scattering parameters.

[0023] The impedance matching network can be an L-type, T-type, inverted L-type, or π-type configuration. Particularly fast impedance matching can be achieved with an L-type configuration. Such configurations can also be mapped relatively easily to a model.

[0024] A target change value for each reactance of the two matching stages can be determined from the intermediate impedance and a model of each matching stage, and the states of the two matching stages can be changed based on the target change values.

[0025] The change target values may be linearly independent, which allows the matching in each matching stage to be performed independently of each other.

[0026] The present invention also provides an impedance matching device, which comprises: a.) an impedance matching network having an input for connection to an RF power generator and an output for connection to a load, in particular to an RF excited plasma processing device, the impedance matching network having at least two matching stages each with a variable reactance; b.) A model of the impedance matching network; c.) an impedance measuring device for measuring input impedance; d.) at least one lookup table, the lookup table containing values that make it possible to deduce an intermediate impedance from the input impedance, the intermediate impedance being in particular the impedance occurring between the matching stages; f.) an identification device for identifying an intermediate impedance based on the measured input impedance and a look-up table, and for identifying at least one target change value for at least one reactance of one matching stage from the intermediate impedance and a model of the impedance matching network; g.) a setting device for changing the state of at least one matching stage based on the determined change target value; An impedance matching device is also included.

[0027] The lookup table preferably has only one dimension. In the simplest case, it contains impedance values for configurable reactances. From this impedance, the intermediate impedance can be calculated via a voltage divider calculation using a model, in particular a circuit model.

[0028] For example, in the case of a T-parameter model, at least some of the T-parameters of the matching stage can be stored in the lookup table. If symmetry considerations can be implemented, storing some of the T-parameters is sufficient. Otherwise, it is conceivable to store all of the T-parameters of the matching stage in the lookup table. The T-parameters (which depend on the state of the matching stage) and the input impedance can be used to estimate the intermediate impedance.

[0029] The model and / or look-up table of the impedance matching network can be stored in memory as a digital model.

[0030] The present invention also provides a computer program product for controlling an impedance matching network, the impedance matching network having an input for connection to an RF power generator and an output for connection to a load, the impedance matching network having at least one first matching stage each with a variable reactance and a second matching stage connected in series, the computer program product comprising, when the program is executed by a computer: a.) determining an intermediate impedance from the measured input impedance and at least one current state value of at least one of the matching stages, the intermediate impedance being in particular the impedance occurring between the matching stages; b.) determining a target change value for at least one reactance of one matching stage from the intermediate impedance and a model of the impedance matching network; c.) outputting a signal to change the state of at least one of the adaptive stages based on the change target value; d.) Repeat steps a.) to c.) Also included is a computer program product comprising instructions for carrying out the method.

[0031] The invention also includes within its scope a non-volatile storage medium having stored thereon instructions for execution by a processor or for configuring a programmable logic component, e.g., an FPGA, to perform steps a.) to d.) of the computer program product.

[0032] In data processing, various data memories that retain the information stored in them permanently, i.e., even when the computer is not running or powered, are called non-volatile (non-transitory) storage media.

[0033] According to the present invention, it is contemplated to create a model of the impedance matching network. This is used to split a two-dimensional problem into two one-dimensional (regular) problems. Knowing the input impedance (measured) and the state of the matching stages, the model allows the identification of a complex load impedance (intermediate impedance) between the two matching stages. At this intermediate impedance, the mappable impedance trajectories of the matching stages must intersect in order to achieve a match. From this condition, the target position (intermediate impedance target value) can be determined.

[0034] According to the present invention, the manipulated variable of the reactance of the matching stage is set based on the determined input impedance and the current state of the matching stage to produce a match at the input of the impedance matching network. By suitable calibration methods, a look-up table can be determined for each matching stage containing the individual impedances of the variable reactance relative to the current state of the matching stage.

[0035] Varying the individual reactances creates individual lines / trajectories in the impedance, admittance, or reflection coefficient plane, starting from the impedance at the input of each matching stage. During matching, the resulting impedance at the input of the second matching stage is determined using the input impedance and the manipulated value of the variable reactance of the first matching stage in conjunction with a lookup table and a matching stage model, which is part of the impedance matching network model. This impedance is the intermediate impedance. The model determines on which trajectory this intermediate impedance must lie so that the first matching stage can transform it to the target value, e.g., 50 ohms. If the reactance is a parallel capacitor, for example, the reciprocal of all matchable impedances of the intermediate impedance must have a real part of 0.02 S. Varying the second reactance of the second matching stage can shift the intermediate impedance along the defined trajectory. In the case of a series element in an L topology, this trajectory is described by the constant real part and variable imaginary part of the intermediate impedance. That is, by changing the reactance of the second matching stage, we can find a setting that puts the midpoint impedance on the locus of the first reactance. This new midpoint impedance forms the intersection of the two loci. At the same time, we can predict what position (state) the first matching stage must take to match this new midpoint impedance.

[0036] For an L-type configuration of the impedance matching network, the calibration, and in particular the creation, of the look-up table can be performed as follows: The first matching stage is a parallel-connected resonant circuit with a variable capacitor, and the second matching stage is a series resonant circuit with respect to the output of the impedance matching network. To calibrate the look-up table, the output of the impedance matching network is first terminated with an open circuit. Then, at the input of the impedance matching network, only the impedance of the parallel element is measured. The impedance of this parallel element is changed by varying the capacitor, and the value is stored in the table. For the series element table, the output is short-circuited, and the parallel element is set to its minimum value (highest impedance). At the input of the impedance matching network, the parallel circuit consisting of the parallel element and the series element is measured. Since the impedance of the parallel element is known, the series element can be calculated and a table for this series element can be determined.

[0037] The intermediate impedance can be calculated directly from the input impedance of the first matching stage and a look-up table of parallel elements. An ideal capacitor changes only the imaginary part of the admittance at the input of the impedance matching network, i.e., 1 / Z inter must have a real part of 0.02S to be matchable. The series element allows the imaginary part of the mid-range impedance to be changed directly. An ellipse results in the admittance plane, which potentially intersects the 0.02S line at two points (depending on the capacitor setting range). The corresponding equating results in a quadratic equation, from which the new series impedance results. From this new series impedance, the new complete mid-range impedance can then also be calculated. It is possible to determine by how much this new complete mid-range impedance must be changed, together with the current value of the parallel impedance, to arrive at an input impedance of 50 ohms.

[0038] The present invention also includes a plasma system designed for the impedance matching method and / or having an impedance matching device as described above, and having a plasma processing device, especially an RF-excited plasma processing device, i.e., a device for performing plasma processing, as a load. The plasma processing device is preferably used for coating (sputtering) and / or etching substrates. The plasma processing device is preferably suitable for use in the manufacture of architectural glass, semiconductors, photovoltaic devices, flat screens, or displays.

[0039] The high frequency of the high frequency power signal may be 1 MHz or higher, and in particular may be in the range of 1 MHz to 200 MHz.

[0040] The power required for powering the plasma process and designed to be provided by the power supply device may be 300 W or more, in particular 1 kilowatt or more. The plasma processing device can be designed so that further power supplies can be connected, with respect to these further power supplies, for example one or more of the following: RF power sources with the same or different RF frequencies; DC power supplies, especially pulsed DC power supplies, MF power supply with a frequency below 1 MHz One or more of the following may be used:

[0041] Further features and advantages of the present invention will become apparent from the following detailed description of an embodiment of the invention, based on the drawings which illustrate essential details of the invention, and from the claims. The features shown in the drawings should not necessarily be understood to be to scale, but are presented so that the uniqueness of the invention can be clearly seen. The different features may be realized individually by themselves or in any combination in a variant of the invention.

[0042] The schematic drawings show an embodiment of the invention and are explained in the following description. [Brief explanation of the drawings]

[0043] [Figure 1] FIG. 1 illustrates an impedance matching device. [Figure 2] 1 shows an admittance plane for explaining the method according to the invention; FIG. [Figure 3] 1 shows an admittance plane for explaining a first method step of the method according to the invention; FIG. [Figure 4] 3 shows an admittance plane for explaining a second method step of the method according to the invention; FIG. [Figure 5] 4 shows admittance planes for explaining the third method step of the method according to the invention; FIG. [Figure 6] FIG. 1 is a block diagram illustrating a method according to the present invention.

[0044] 1 shows an impedance matching device 1 comprising an impedance matching network 2 having an input 3 and an output 4. An RF power generator 5 can be connected to the input 3, and a load 6, particularly a plasma processing device, can be connected to the output 4. The RF power generator 5 can generate high frequency power at frequencies above 1 MHz, particularly in the range of 1 MHz to 200 MHz.

[0045] The input impedance Z at the input 3 of the impedance matching network 2 in can be detected by the impedance measuring device 7. The impedance measuring device 7 measures the complex input impedance Z in The impedance measuring device 7 can be configured, for example, as a V / I probe, i.e., configured to measure voltage and current, in particular voltage and current, including their phase relationship to one another.

[0046] The illustrated impedance matching network 2 has an L-type configuration with a first matching stage 10 and a second matching stage 12 arranged in series with the first matching stage 10. The first matching stage 10 has a variable reactance XP, which in the illustrated embodiment is configured as a capacitor, arranged in series with an inductance L1.

[0047] The second matching stage 12 similarly comprises a variable reactance XS configured as a capacitor, which is connected in series with the inductance L2.

[0048] Intermediate impedance Z inter is the impedance at the input of the second matching stage 12.

[0049] The impedance measuring device 7 measures the input impedance Z of the impedance matching network 2. in The measured input impedance Z in is the measured input impedance Z in and determining an intermediate impedance Z based on at least one look-up table 16, 18. inter The look-up tables 16, 18 can be used by the identification device 14 to identify the impedance of the reactances XP, XS. The look-up tables 16, 18 are created in a calibration method. The look-up tables 16, 18 can have configurable impedance values of the reactances XP, XS for different states of the reactances XP, XS and therefore for different states of the matching stages 10, 12.

[0050] The identifying device 14 has an intermediate impedance Z inter and a model 20 of the impedance matching network 2, the method is further configured to determine at least one target change value for at least one reactance XP, XS of one matching stage 10, 12.

[0051] The setting device 22 is configured to change the state of at least one matching stage 10, 12 based on the identified change target value.

[0052] Figure 2 shows the input admittance, i.e., 1 / Z in The admittance plane of Z in is the impedance Z measured at the input of the impedance matching network 2 in represents Z. intarget represents the admittance to be achieved by the impedance matching. By varying the reactance XP of the first matching stage 10, only the imaginary part of the input admittance can be varied, as indicated by the vertical double arrow 30.

[0053] The reactance XS of the second matching stage 12 causes the input admittance to move on an elliptical trajectory, as indicated by the arrow 32 .

[0054] Input admittance (Z in ) is known and the value of XP is known, the intermediate impedance Z inter It can be seen from Figure 3 that it is possible to determine the ellipse on which the admittance change occurs by changing the reactance XS.

[0055] Now, in order to make the ellipse or trajectory T intersect with the target line ZL, i.e. Z inter We can determine how much reactance XS must be changed in order for the real part of to take on a value of 0.02 S. From this, we can determine the target change dXS.

[0056] Now, in a further step, which will be explained based on FIG. intargetThis gives us the target further change, dXP.

[0057] The method according to the invention is further explained based on the block diagram of Fig. 6. In step 100, the input impedance Z of the impedance matching network is in Then, in step 101, the measured input impedance Z in and at least one current state value of at least one matching stage of the impedance matching network.

[0058] In step 102, a target change value for at least one reactance of one matching stage is identified from the intermediate impedance and a model of the impedance matching network.

[0059] In step 103, the state of at least one of the matching stages is changed based on the change target value. In step 104, it is checked whether the input impedance determined here is above or below a predetermined value. If it is not above or below the predetermined value, the process returns to step 100. If not, matching has been achieved.

Claims

1. A method for impedance matching by an impedance matching network (2), comprising: The impedance matching network (2) comprises an input (3) for connection to an RF power generator (5) and an output (4) for connection to a load (6), in particular to an RF excited plasma processing device; The impedance matching network (2) comprises at least one first matching stage (10) each having a variable reactance (XP, XS) and a second matching stage (12) connected in series; The method comprises: a) Input impedance (Z ｉｎ ) measuring the b) the measured input impedance (Z ｉｎ ) and at least one current state value of at least one of the matching stages to calculate an intermediate impedance (Z ｉｎｔｅｒ ) and determining the intermediate impedance (Z ｉｎｔｅｒ ) is the impedance occurring between the matching stages (10, 12); c) the intermediate impedance (Z ｉｎｔｅｒ ) and a model of the impedance matching network (2), determining a change target value (dXP, dXS) for at least one reactance (XP, XS) of one matching stage (10, 12); d) changing the state of at least one of the matching stages (10, 12) based on the change target values (dXP, dXS); e) repeating steps a) to d); Equipped with The method, wherein the change target values (dXP, dXS) are determined based on an intermediate impedance target value (Z intersoll ).

2. The steps a) to d) are performed by adjusting the input impedance (Z ｉｎ ) is repeated until it exceeds or falls below a predetermined value, The method of claim 1.

3. As the state value, the position (XP, XS) of a mechanically variable reactance or the switching state of an electronically variable reactance is detected.

3. The method according to claim 1 or 2.

4. The intermediate impedance (Z ｉｎｔｅｒ ) is the intermediate impedance (Z ｉｎｔｅｒ ) and the input impedance (Z ｉｎ ) is determined depending on the state based on a correspondence between 4. The method according to any one of claims 1 to 3.

5. The intermediate impedance target value (Z ｉｎｔｅｒｓｏｌｌ ) is determined based on at least one predetermined boundary condition, 5. The method according to any one of claims 1 to 4.

6. changing the state of at least one of the matching stages by the target change value or in the direction of the target change value; 6. The method according to any one of claims 1 to 5.

7. The states of the two matching stages (10, 12) are changed simultaneously.

7. The method according to any one of claims 1 to 6.

8. A circuit model is used as a model of the impedance matching network (2), 8. The method according to any one of claims 1 to 7.

9. A transmission parameter model, a scattering parameter model, or a parameter model derivable from the transmission parameter model or the scattering parameter model is used as a model of the impedance matching network (2).

8. The method according to any one of claims 1 to 7.

10. The impedance matching network (2) may be configured as an L-type, T-type, inverted L-type, or π-type.

10. The method according to any one of claims 1 to 9.

11. A change target value (dXP, dXS) for each reactance (XP, XS) of the two matching stages (10, 12) is set to the intermediate impedance (Z ｉｎｔｅｒ ) and a model of each of said matching stages (10, 12), The states of the two matching stages (10, 12) are changed based on the change target values (dXP, dXS).

11. The method according to any one of claims 1 to 10.

12. The change target values (dXS, dXP) are linearly independent. The method of claim 11.

13. An impedance matching device (1), The impedance matching device (1) comprises: a. an impedance matching network (2) having an input (3) for connection to an RF power generator (5) and an output (4) for connection to a load (6), in particular an RF excited plasma processing device, said impedance matching network (2) having at least two matching stages (10, 12) each with a variable reactance (XP, XS); b. A model of the impedance matching network (2); c) an impedance measuring device for measuring the input impedance; d. At least one look-up table (16, 18), wherein the look-up table (16, 18) includes an input impedance (Z ｉｎ ) to the intermediate impedance (Z ｉｎｔｅｒ ) and the intermediate impedance (Z ｉｎｔｅｒ ) is the impedance occurring between the matching stages (10, 12), at least one look-up table (16, 18); e. Measured input impedance (Z ｉｎ ) based on the intermediate impedance (Z ｉｎｔｅｒ ) and for identifying the intermediate impedance (Z ｉｎｔｅｒ an identification device (14) for identifying at least one target change value (dXP, dXS) for at least one reactance (XP, XS) of one matching stage (10, 12) from the model of the impedance matching network (2) and the impedance matching network; f. a setting device (22) for changing the state of at least one matching stage (10, 12) based on the determined change target values (dXP, dXS); Equipped with The impedance matching device (1), wherein the change target values (dXP, dXS) are specified based on an intermediate impedance target value (Z intersoll ).

14. A computer program product for controlling an impedance matching network (2), comprising: The impedance matching network (2) has an input (3) for connection to an RF power generator (5) and an output (4) for connection to a load (6); The impedance matching network (2) comprises at least one first matching stage (10) each having a variable reactance (XP, XS) and a second matching stage (12) connected in series; The computer program product, when executed by a computer, a) Measured input impedance (Z ｉｎ ) and at least one current state value of at least one of the matching stages (10, 12) to calculate an intermediate impedance (Z ｉｎｔｅｒ ) and determining the intermediate impedance (Z ｉｎｔｅｒ ) is the impedance occurring between the matching stages (10, 12); b) the intermediate impedance (Z ｉｎｔｅｒ ) and a model of the impedance matching network (2), determining a change target value (dXP, dXS) for at least one reactance (XP, XS) of one matching stage (10, 12); c) outputting a signal for changing the state of at least one of the matching stages (10, 12) based on the change target values (dXP, dXS); d) repeating steps a) to c); including an order to implement The change target values (dXP, dXS) are determined based on an intermediate impedance target value (Z intersoll ).

15. A non-volatile storage medium having stored thereon instructions for execution by a processor or for configuring a programmable logic component to perform steps a) through d) of claim 14.

16. 15. A plasma system designed for a method for impedance matching according to any one of claims 1 to 12 and / or comprising an impedance matching device according to claim 14, and comprising a plasma processing device, in particular an RF excited plasma processing device, as a load (6).

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