Impedance matching circuit, plasma process supply system and plasma process system
Patent Information
- Application Number
- DE112024001051
- Authority / Receiving Office
- DE · DE
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-02-28
- Filing Date
- 2024-02-27
- Publication Date
- 2025-12-24
AI Technical Summary
Existing impedance matching circuits for plasma processing systems have limited discrete output impedances, leading to inefficiencies and potential damage to semiconductor switches due to inadequate current and voltage handling, which restricts the compact design and fine-tuning of impedance matching in high-frequency applications.
An impedance matching circuit with a first unit for predetermined impedance transformation and a second unit with adjustable reactances and semiconductor switching elements, allowing for continuous impedance variation within safe voltage and current limits, reducing the need for parallel or series connections of semiconductor switches and avoiding over-stressing.
This solution increases the number of possible output impedances, enables a compact design, and ensures semiconductor switches operate within safe limits, enhancing the efficiency and reliability of plasma processing systems by minimizing power reflection and preventing switch damage.
Abstract
Description
[0001] Impedance matching circuit, plasma process supply system and plasma process system
[0002] The invention relates to an impedance matching circuit for power
[0003] > 500 W, preferably > 2 kW and frequencies in the range from 2 to 100 MHz, in particular in the range from 10 MHz to 50 MHz, a plasma process supply system and a plasma process system.
[0004] Such an impedance matching circuit can be used in systems in which a load is supplied with electrical power, particularly high-frequency power. "High frequency" is also abbreviated to "HF" below. Here, "HF" refers to frequencies in the range from 2 MHz to 100 MHz, particularly in the range from 10 MHz to 50 MHz.
[0005] In such a system, the load impedance should be matched to the impedance of the power supply, otherwise power reflection may occur. Power reflection has a direct impact on the efficiency of a system; it reduces its efficiency.
[0006] An example system in which an impedance matching circuit may be used may be a plasma processing system.
[0007] Such a plasma processing system may, for example, be a system in which a load, e.g. a plasma processing arrangement, is supplied with electrical power.
[0008] Such a plasma processing arrangement can, for example, be a plasma processing chamber that is used for industrial plasma processes such as the surface treatment of workpieces, semiconductor manufacturing with plasma or the processing of workpieces with gas lasers.
[0009] In such an application, the plasma process arrangement serves to generate plasma.
[0010] For this purpose, a plasma processing arrangement may comprise an electrode which is fed with a high-frequency power signal for generating the plasma, hereinafter referred to as the RF power signal.
[0011] Typically, a high-power and especially high-voltage supply is required, for which the plasma processing system can be connected to a high-frequency power supply, referred to below as an RF power supply. The plasma process occurring in the plasma processing system has the problem that the electrical load impedance of the plasma processing system, which occurs during the process, depends on the conditions within the plasma processing system and can vary greatly. In particular, the properties of the workpiece, electrode, and gas conditions are important.
[0012] For this reason, an impedance matching circuit is usually required to transform the load impedance to a nominal impedance of the RF power supply. Such an impedance matching circuit is typically placed between an RF power supply and the plasma processing device, usually in close proximity to the plasma processing device.
[0013] An impedance matching circuit is typically an arrangement that may contain inductances and / or capacitances.
[0014] For complex problems where it is important to be able to quickly change the impedance, semiconductor-switched impedance matching circuits are often used. These semiconductor switching elements can be used to switch inductors and / or capacitances in impedance matching circuits on and off. Control circuits can be used to control the switching on and off of the semiconductor switching elements. An example of such a semiconductor-switched impedance matching circuit is disclosed and described in DE 20 2020 102 084 U1.
[0015] Due to their design principle, such semiconductor-switched impedance matching circuits only have a discrete set of possible output impedances at a given frequency. However, the finest possible adjustment is desirable. This would require a relatively large number of semiconductor switches. This, however, contradicts the need for the most compact design possible. A design that is as compact as possible is fundamentally desirable, since space in such a plasma process system is often limited. The present invention is therefore based on the object of providing an impedance matching circuit that increases the set of possible output impedances and enables a continuously variable output impedance at least for one range, as well as more advantageously utilizing the components used, thus enabling a compact design. This object is achieved by an impedance matching circuit according to independent claim 1.Advantageous further developments of the invention emerge from the subclaims and / or the description.
[0016] According to the present invention, an impedance matching circuit for powers > 500 W and frequencies in the range from 2 MHz to 100 MHz is proposed, in particular for a plasma process supply system and plasma process system, comprising: a) a first impedance matching unit, comprising one or more reactances, which is designed to carry out a first predetermined impedance transformation from its input terminal to its output, b) a second impedance matching unit, which is designed to carry out a second predetermined impedance transformation with an adjustable transformation ratio from its input terminal to its output, wherein the second impedance matching unit comprises: i) one or more reactances and ii) a semiconductor switching element, wherein the transformation ratio can be changed in predetermined steps by the semiconductor switching element during operation, and iii) an electrically continuously variable reactance,wherein the transformation ratio is continuously variable during operation by the electrically continuously variable reactance, c) wherein the semiconductor switching element and / or the electrically continuously variable reactance are operable up to a maximum permissible voltage and a maximum permissible current, d) wherein the first impedance matching unit is designed to carry out the first predetermined impedance transformation in such a way that i) the conductance of the impedance at the input or output of the second impedance matching unit is greater than the conductance of the impedance,which would occur at the input or output of the second impedance matching unit at the rated power of the impedance matching unit and the maximum permissible voltage of the at least one semiconductor switching element and / or the electrically continuously variable reactance; and ii) the resistance of the impedance at the input or output of the second impedance matching unit is greater than the resistance of the impedance that would occur at the input or output of the second impedance matching unit at the rated power and the maximum permissible current of the at least one semiconductor switching element and / or the electrically continuously variable reactance.
[0017] As mentioned previously, a semiconductor-switched impedance matching circuit has only a discrete set of possible output impedances. If the design of the impedance matching circuit is to be as compact as possible, it is important to keep the number of semiconductor switching elements to a minimum. This means, firstly, that these semiconductor switching elements should not be constructed from parallel and / or series circuits of multiple switching components. Secondly, this means that the steps between the adjustable values can become quite large.
[0018] Due to all these limitations, the reflection factor cannot be trimmed to zero for all plasma impedance values, as the available discrete impedances cannot convert every complex impedance to zero. However, reflected power is a common measure of the quality of power matching in plasma applications. Getting it to zero is therefore often necessary for product acceptance in this market.
[0019] In addition, semiconductor-switched impedance matching circuits face the problem that, depending on the load condition, the current and voltage carrying capacity of the semiconductor switches is insufficient. Thus, the current and voltage carrying capacity of the actual semiconductor switches determines the maximum transmittable power of such an impedance matching circuit. It has been shown that neither in a 50-ohm system nor directly at the plasma process chamber are the impedances suitable for utilizing both the current and voltage limits of a semiconductor switching element in two switching positions. In principle, it can be stated that the semiconductor switching elements are not being switched within their optimal range.
[0020] Either the current and / or voltage are too low, so the semiconductor switching elements are not fully driven, or the current and voltage are so high that the semiconductor switching elements could be damaged. The latter scenario is something we want to avoid, so in the current state of the art, the semiconductor switches are never fully utilized.
[0021] The inventive dimensioning of the impedance matching circuit, which was determined through calculations, simulations, circuit design, tests, and investigations, ensures that the at least one semiconductor switching element is fully utilized, but not overloaded. It was determined that the impedance matching unit must meet the above-mentioned criteria regarding the transformation of the input impedance to an intermediate impedance, wherein the input impedance is preferably constant and more preferably corresponds to 50 ohms. As a result of this and the maximum permissible voltage and the maximum permissible current of the semiconductor switching element, the transformation ratio, which is set by the first impedance matching unit, can be precisely calculated. The at least one semiconductor switching element is thereby precisely not overloaded, but switches currents and voltages that are below the maximum permissible values.As a result, the at least one semiconductor switching element is fully controlled, which in turn means that the semiconductor switching element does not have to be oversized, which in turn saves costs. The dimensioning rule ensures that no critical situations arise with regard to the current and voltage strength of the at least one semiconductor switching element. In the impedance matching circuit according to the invention, it is particularly possible to dispense with connecting several semiconductor switching elements in parallel and / or in series. This is advantageous because the effort required to actually switch the several semiconductor switching elements at the same time would be very high. If one semiconductor switching element switches slightly later than the other semiconductor switching elements, this can lead to the destruction of the impedance matching circuit. However, the dimensioning according to the invention successfully avoids this.The dimensioning ensures that, for a defined input impedance, which is specified in particular by the RF power supply, no operating situation arises for the at least one semiconductor switching element in which the at least one semiconductor switching element could be destroyed. The at least one semiconductor switching element only has to switch currents and / or voltages that are below the maximum permissible voltage and / or the maximum permissible current. An additional control loop for measuring voltages and / or currents and making the switching behavior dependent thereon is therefore not necessary. As a result, the semiconductor switching element does not have to be significantly oversized, as is the case with impedance matching circuits from the prior art, whereby the impedance matching circuit according to the invention is cheaper to manufacture.
[0022] For the term "conductance" of a complex impedance Z, it should generally be understood that the conductance is real and equal to G, with the following relationship: Z = 1 / Y = 1 / (G + jB).
[0023] The conductance of the intermediate impedance Zi is therefore Gi, where: Zi = 1 / Yi = 1 / (Gi + jBi).
[0024] The conductance of the output impedance Zp is therefore GP, where: Zp = 1 / Yp = 1 / (GP + jBp).
[0025] B, Bi, Bp are each the imaginary part of the complex conductance Y, Yi, Yp.
[0026] For the term "resistance" of a complex impedance Z, it should generally be understood that the resistance is real and equal to R, with the following relationship: Z = R + jX.
[0027] The resistance of the intermediate impedance Zi is therefore Ri, where: Zi = Ri + jXi. The resistance of the output impedance Zp is therefore Rp, where: Zp = Rp + jXp.
[0028] X, Xi, Xp are each the imaginary part of the complex impedance Z, Zi, Zp.
[0029] In a preferred embodiment, the first impedance matching unit is designed such that the conductance of the impedance at the input of the second impedance matching unit is greater than the conductance of the impedance that would occur at the input of the second impedance matching unit at the rated power of the impedance matching unit and the maximum permissible voltage of the at least one semiconductor switching element and / or the electrically continuously variable reactance; and the resistance of the impedance at the input of the second impedance matching unit is greater than the resistance of the impedance that would occur at the input of the second impedance matching unit at the rated power and the maximum permissible current of the at least one semiconductor switching element and / or the electrically continuously variable reactance
[0030] By using an electrically continuously variable reactance in the impedance matching circuit, the number of possible output impedances can be increased and a continuously variable output impedance can be achieved, at least for a certain range.
[0031] This certain range can advantageously be limited upwards by the impedance of the impedance matching circuit without the electrically continuously variable reactance added to the largest possible impedance of the electrically continuously variable reactance. The lower limit can advantageously be limited by the impedance of the impedance matching circuit without the electrically continuously variable reactance added to the smallest possible impedance of the electrically continuously variable reactance.
[0032] The largest and smallest possible impedance of the electrically continuously variable reactance depends on the component. Between these two limits, the electrically continuously variable reactance is continuously adjustable. The impedance can be adjusted, for example, by applying a control voltage. The electrically continuously variable reactance can be implemented either as an electrically continuously variable capacitance or as an electrically continuously variable inductance. An electrically continuously variable capacitance can be, for example, a varactor. An electrically continuously variable inductance can be, for example, a transductor. A transductor is understood here to be an electromagnetic component for controlling alternating currents by electrical signals, in particular direct currents, in particular by pre-magnetizing the magnetic core of a choke.
[0033] In an advantageous embodiment of the impedance matching circuit, the input impedance is essentially constant during operation of the impedance matching circuit and equal to the specified target input impedance. This, on the one hand, presents a constant impedance to the RF power supply, and on the other hand, the constant transformation ratio from the input impedance to the intermediate impedance by the first impedance matching unit ensures that the at least one semiconductor switching element is always operated within the tolerances and at a high level of control.
[0034] In one embodiment, the first impedance matching unit of the impedance matching circuit can be implemented with exclusively fixed reactances. Such an implementation is cost-effective and robust.
[0035] In one embodiment, the impedance matching unit can comprise a plurality of semiconductor switching elements and one or more control circuits associated with each of these semiconductor switching elements, wherein the semiconductor switching elements are each designed to switch reactances on and off. This allows a wide range of impedance matching to be covered while simultaneously achieving a compact design.
[0036] In one embodiment, the at least one semiconductor switching element of the second impedance matching unit can be a transistor or a diode. This allows the transformation ratio to be changed particularly quickly during operation. A transistor can be embodied as a metal-oxide-semiconductor field-effect transistor (MOSFET). A switching diode can be embodied, for example, as a PIN diode.
[0037] The at least one semiconductor switching element can also be cooled by a fluid. The fluid can be water, for example. This also includes distilled water. For cooling, the semiconductor switching element can be arranged on a heat sink. This heat sink can be made, in particular, of metal, e.g., of aluminum and / or copper. The heat sink can further have at least one channel through which the fluid can flow and dissipate the heat of the semiconductor switching element.
[0038] In one embodiment, the impedance matching circuit can be used in a plasma process supply system or a plasma process system.
[0039] Such a plasma process supply system may include, in addition to the impedance matching circuit, an RF power supply for providing the RF power signal. The impedance matching circuit may be electrically connected to the RF power supply and may be configured to be connected to a plasma process arrangement.
[0040] In a plasma processing system, such a plasma processing arrangement may be present and connected to the plasma processing supply system. The plasma processing arrangement may be supplied with power from the RF power signal via the plasma processing supply system.
[0041] Preferred embodiments of the invention are illustrated schematically in the drawings and are explained in more detail below with reference to the figures of the drawing.
[0042] They show:
[0043] Fig. 1 shows a schematic view of a first embodiment of a plasma process system with an impedance matching circuit according to the invention; Fig. 2a, b show various embodiments of a first impedance matching unit of an impedance matching circuit according to the invention;
[0044] Fig. 3a-f show various embodiments of a second impedance matching unit of an impedance matching circuit according to the invention;
[0045] Fig. 4a-d various embodiments of electrically continuously variable reactances;
[0046] Fig. 5 shows an embodiment of a measuring unit of a plasma process supply system;
[0047] Fig. 6 shows part of a measuring unit of a plasma process system.
[0048] Fig. 1 shows a plasma process system 100 comprising a plasma process supply system 108. The plasma process supply system 108 has an impedance matching circuit 1 according to the invention and an RF power supply 101. The plasma process supply system 108 is designed to be connected to at least one consumer 102, in particular a plasma process arrangement, e.g., in the form of a plasma process chamber. If the plasma process supply system 108 is connected to a described consumer 102, as shown in Fig. 1, it forms a plasma process system 100. The RF power supply 101 is designed to provide an RF signal, in particular in the form of a uniform signal, also called a continuous wave signal, or CW signal for short, with a nominal power PNom. The impedance matching circuit 1 comprises an input terminal 2, wherein the RF power supply 101 is connected to the input terminal 2.The impedance matching circuit 1 further comprises an output terminal 3.
[0049] The output terminal 3 is connected to the at least one load 102. The RF power supply 101 is preferably connected to the impedance matching circuit 1 via a first cable arrangement 4. The impedance matching circuit 1 is preferably connected to the load 102 via a second cable arrangement 5. The first and / or second cable arrangement 4, 5 can comprise one or more cables, for example, connected in series and / or in parallel. Coaxial cables are preferably used.
[0050] The consumer 102, in this case the plasma processing arrangement in the form of a plasma processing chamber, comprises at least one electrode 103 for generating a plasma 104. The electrode 103 is connected to the output terminal 3 of the impedance matching circuit 1.
[0051] The plasma process supply system 108 further comprises a control and / or detection device 105. This can preferably comprise a processor and / or a programmable logic component, in particular an FPGA and / or microcontroller and / or a preconfigured logic component, in particular an ASIC. The control and / or detection device 105 can also comprise a memory unit. The control and / or detection device 105 is designed to control the RF power supply 101, in particular to activate or deactivate it. Additionally or alternatively, the control and / or detection device 105 is also designed to change the power and / or frequency of the RF signal. Additionally or alternatively, the control and / or detection device 105 is designed to change the waveform, in particular the type of the RF signal or modulation of the RF signal.
[0052] The control and / or detection device 105 is preferably also designed to control the impedance matching circuit 1. In particular, the control and / or detection device 105 is designed to change the transformation ratio within the impedance matching circuit 1.
[0053] The plasma process supply system 108 preferably also comprises a measuring unit 106. The measuring unit 106 is arranged between the RF power supply 101 and the impedance matching circuit 1. The measuring unit 106 can, for example, comprise at least one directional coupler or a current sensor and a voltage sensor. Using the at least one directional coupler, the measuring unit 106 can measure the power of the RF signal transmitted from the RF power supply 101 toward the impedance matching circuit 1. Preferably, the measuring unit 106 can also measure the power of an RF signal reflected back at the impedance matching circuit 1 toward the RF power supply 101. The power of the RF signal transmitted from the RF power supply 101 toward the impedance matching circuit 1 can also be determined using the current sensor and the voltage sensor.A power of an RF signal reflected by the impedance matching circuit 1 can also be detected by the current sensor and the voltage sensor.
[0054] The plasma process supply system 108 preferably also comprises an operating unit 107. The operating unit 107 preferably has a screen, in particular a touch-sensitive screen. In addition to a screen, the operating unit 107 can also comprise input means such as a keyboard and / or mouse. The operating unit 107 can also be a web server that provides data and receives user input. The control and / or detection device 105 is designed to display current settings of the RF power supply 101 and / or the impedance matching circuit 1 on the operating unit 107. The control and / or detection device 105 can also be designed to display the measured values received by the measuring unit 106 on the operating unit 107.The control and / or detection device 105 is preferably designed 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 107 and to generate corresponding manipulated variables for the RF power supply 101 and to transmit them to the latter.
[0055] Before explaining the impedance matching circuit 1 according to the invention in detail, reference is made to Figures 5 and 6, which describe the measuring unit 106. In this exemplary embodiment, the measuring unit 106 is designed to measure a voltage and a current without contact. For this purpose, the measuring unit 106 comprises a current sensor 110 and a voltage sensor 111. These are shown in detail in Figures 5 and 6.
[0056] Preferably, however, the phase relationship between current and voltage is also measured. Current sensor 110 of measuring unit 106 is a coil, particularly in the form of a Rogowski coil.
[0057] Both ends of the coil are preferably connected to each other via a shunt resistor 112. The voltage drop across the shunt resistor 112 can be digitized using a first A / D converter 113.
[0058] The voltage sensor 111 of the measuring unit 106 is preferably designed as a capacitive voltage divider. A first capacitance 114 is formed by an electrically conductive ring 114. An electrically conductive cylinder could also be used. The first cable arrangement 4 is routed through this electrically conductive ring 114. A second capacitance 115 of the voltage sensor 111, which is designed as a voltage divider, is connected to the reference ground. Connected in parallel to the second capacitance 115 is a second A / D converter 116, which is designed to detect and digitize the voltage drop across the second capacitance 115.
[0059] In principle, the measuring unit 106 can also be arranged or constructed on a (common) printed circuit board. The first capacitor 114 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 cable arrangement 4 is guided through an opening in the printed circuit board. The second capacitor 115 can be formed by a discrete component.
[0060] The current sensor 110 in the form of a coil, in particular in the form of a Rogowski coil, is spaced further from the first cable arrangement 4 than the first capacitor 114. 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 run through a common plane. The shunt resistor 112 can also be arranged on this circuit board. The same applies to the first and / or second A / D converters 113, 116. The first and / or second A / D converters 113, 116 are read and / or controlled by the control and / or detection device 105.
[0061] The control and / or detection device 105 is preferably designed to control the impedance matching circuit 1 based on the measured values of the measuring unit 106.
[0062] Referring again to Fig. 1 below, the structure of the impedance matching circuit 1 is explained in more detail. The impedance matching circuit 1 comprises a first impedance matching unit 6 and a second impedance matching unit 7. The first impedance matching unit 6 is electrically connected to the input terminal 2.
[0063] The first impedance matching unit 6 is designed to transform an input impedance Zo, which is applied to the input terminal 2, into an intermediate impedance Zi. The intermediate impedance Zi is applied to an output 9 of the first impedance matching unit 6. The transformation ratio is fixed during operation. In Fig. 1, the first impedance matching unit 6 has an inductance L2 and a capacitor C2, which are connected in an L-shape. Many other designs are conceivable; some further designs are shown by way of example in Fig. 2a and Fig. 2b. The second impedance matching unit 7 is connected to the first impedance matching unit 6 in the transmission direction of the RF signal from the RF power supply 101 to the load 102. In particular, the second impedance matching unit 7 comprises an input 10, which is connected to the output terminal 9 of the first impedance matching unit 6, or which is directly connected to the output 9.The intermediate impedance Zi is therefore also present at input 10. The second impedance matching unit 7 is designed to transform the intermediate impedance Zi at its input 10 to an output impedance Zp at the output terminal 3, wherein the transformation ratio can be changed during operation by at least one semiconductor switching element 14. In Fig. 1, the second impedance matching unit 7 has, by way of example, an electrically continuously variable reactance 16 connected in parallel to a series circuit comprising a capacitor C3 and a semiconductor switching element 14.
[0064] The at least one semiconductor switching element 14 of the second impedance matching unit 7 is operable up to a maximum permissible voltage and up to a maximum permissible current. The intermediate impedance Zi, to which the first impedance matching unit 6 transforms the input impedance Zo, is selected for a predetermined target input impedance such that: a) the conductance Gi of the intermediate impedance Zi is greater than the conductance of the impedance that would occur at the input 10 of the second impedance matching unit 7 at the rated power PNenn of the impedance matching circuit 1 and the maximum permissible voltage of the at least one semiconductor switching element 14; and b) the resistance Ri of the intermediate impedance Zi is greater than the resistance of the impedance that would occur at the input 10 of the second impedance matching unit 7 at the rated power PNenn and the maximum permissible current of the at least one semiconductor switching element 14.
[0065] The rated power PNom of the impedance matching circuit 1 is preferably identical to the rated power PNom of the RF power supply 101.
[0066] A transmission path for transmitting the RF signal runs between the input terminal 2 and the output terminal 3 of the impedance matching circuit 1. The first and second impedance matching units 6, 7 are arranged in the transmission path.
[0067] The following figures explain in more detail a possible configuration of the first and second impedance matching units 6, 7 of the impedance matching circuit 1. Figures 2a and 2b show two different circuit diagrams of the first impedance matching unit 6, which in these embodiments do not include a semiconductor switching element 14.
[0068] Fig. 2a shows an embodiment of the first impedance matching unit 6 in an L-shape, which has an inductance L2a and a capacitance C2a. The inductance L2a is connected from the input terminal 2 to ground. The capacitance C2a is connected between the input terminal 2 and the output 9 of the first impedance matching unit 6. This first impedance matching unit 6 is designed to transform the input impedance Zo at the input terminal 2 to an intermediate impedance Zi at its output 9.
[0069] Fig. 2b shows another embodiment of the first impedance matching unit 6 in n-type, which has an inductor L2b and two capacitors C2b, C2b'. The inductor L2b is connected from the input terminal 2 to ground. The capacitor C2b is connected between the input terminal 2 and the output 9 of the first impedance matching unit 6. The capacitor C2b' is connected from the output 9 to ground.
[0070] This first impedance matching unit 6 is designed to transform the input impedance Zo at the input terminal 2 to an intermediate impedance Zi at its output 9.
[0071] Figs. 3a to f show various circuit diagrams of the second impedance matching unit 7a-7f, which in these exemplary embodiments is implemented with one or more semiconductor switching elements 14a-14f and one or more control circuits 15a-15f. The second impedance matching units 7a-7f further have a first terminal 11 and a second terminal 12, to which an electrically continuously variable reactance 16 is connected (shown in Figs. 4b to 4d). Possible embodiments and functions of this electrically continuously variable reactance 16 are discussed in more detail in the descriptions of Figs. 4a to 4d.
[0072] Fig. 3a shows an embodiment of the second impedance matching unit 7a in an L-shape, which has an inductance L3a and two capacitors C3a, C3a'. The inductance L3a is connected between the input 10 and the output terminal 3. The capacitors C3a, C3a' are connected in series, and this series connection is connected from the input 10 to ground. The capacitor C3a' is connected directly to ground. A semiconductor switching element 14a is connected in parallel with the capacitor C3a'. Furthermore, an electrically continuously variable reactance 16 (shown in Fig. 4a to d) is connected in parallel with the capacitor C3a' and the semiconductor switching element 14a.
[0073] The semiconductor switching element 14a is connected to a control circuit 15a, which is configured to switch the semiconductor switching element 14a on and off. When the semiconductor switching element 14a is switched on, the capacitance C3a' and the electrically continuously variable reactance 16 are short-circuited, and the resulting capacitance of the series circuit is equal to the capacitance C3a. When the semiconductor switching element 14a is switched off, the capacitance C3a' is not short-circuited, and the resulting impedance of the series circuit is equal to that of a series circuit of the capacitance C3a and the parallel circuit of the capacitance C3a' and the electrically continuously variable reactance 16.
[0074] This second impedance matching unit 7a is designed to transform the intermediate impedance Zi at its input 10 to an output impedance Zp at the output terminal 3, wherein the transformation ratio can be changed during operation by the semiconductor switching element 14a and the electrically continuously variable reactance 16.
[0075] Fig. 3b shows a further embodiment of the second impedance matching unit 7b, which has two capacitors C3b, C3b'. The capacitor C3b is connected in series with a semiconductor switching element 14b. This series circuit comprising the capacitor C3b and the semiconductor switching element 14b is connected between the input 10 and the output terminal 3. The capacitor C3b' is connected in parallel with the semiconductor switching element 14b. Furthermore, an electrically continuous reactance 16 (shown in Fig. 4a to d) is connected in parallel with the capacitor C3b' and the semiconductor switching element 14b via the two terminals 11, 12. The semiconductor switching element 14b is connected to a control circuit 15b, which is configured to switch the semiconductor switching element 14b on and off.When the semiconductor switching element 14b is turned on, the capacitance C3b' and the electrically continuously variable reactance 16 are short-circuited, and the resulting capacitance of the second impedance matching unit 7b is equal to the capacitance C3b. When the semiconductor switching element 14b is turned off, the capacitance C3b' is not short-circuited, and the resulting impedance of the second impedance matching unit 7b is equal to that of a series connection of the capacitance C3b and the parallel connection of the capacitance C3b' and the electrically continuously variable reactance 16.
[0076] This second impedance matching unit 7b is designed to transform the intermediate impedance Zi at its input 10 to an output impedance Zp at the output terminal 3, wherein the transformation ratio can be changed during operation by the semiconductor switching element 14b and the electrically continuously variable reactance 16.
[0077] Fig. 3c shows a further embodiment of the second impedance matching unit 7c, which comprises a series connection of the two second impedance matching units 7a, 7b from Fig. 3a and Fig. 3b. This series connection is connected between input 10 and output terminal 3. The function of the second impedance matching unit 7c, i.e. the series connection of the two second impedance matching units 7a, 7b, results from the functional modes of the individual impedance matching units 7a, 7b described in the descriptions of Fig. 3a and Fig. 3b, only combined as a series connection.
[0078] This second impedance matching unit 7c is designed to transform the intermediate impedance Zi at its input 10 to an output impedance Zp at the output terminal 3, wherein the transformation ratio can be changed during operation by the semiconductor switching elements 14a, 14b and the electrically continuously variable reactance 16.
[0079] Fig. 3d shows a further embodiment of the second impedance matching unit 7d in L-shape, which has an inductance L3d, a capacitance C3d, three further capacitances C3d', and three semiconductor switching elements 14d. The inductance L3d is connected between the input 10 and the output terminal 3. The capacitance C3d is connected in series with a parallel circuit comprising the three further capacitances C3d' and the three semiconductor switching elements 14d. This parallel circuit has three parallel-connected series circuits comprising a capacitance C3d' and a semiconductor switching element 14d, as well as an electrically continuously variable reactance 16 connected in parallel thereto (shown in Fig. 4a to d). Each semiconductor switching element 14d is connected to a control circuit 15d, which is configured to switch the semiconductor switching elements 14d on and off.When one of the three semiconductor switching elements 14d is switched on, the capacitance C3d is connected in series with the parallel circuit comprising one of the three capacitances C3d' and the electrically continuously variable reactance 16. This series circuit is connected from input 15 to ground. If another or both of the additional semiconductor switching elements 14d are also switched on, the capacitance C3d is connected in series with a parallel circuit comprising two or three of the capacitances C3d' and the electrically continuously variable reactance 16. This parallel circuit can be expanded by additional parallel series circuits, but can also have only two parallel series circuits and the electrically continuously variable reactance 16. When all semiconductor switching elements 14d are switched off, a series circuit comprising the capacitance C3d and the electrically continuously variable reactance 16 results.This series circuit is connected from input 10 to ground.
[0080] This second impedance matching unit 7d is designed to transform the intermediate impedance Zi at its input 10 to an output impedance Zp at the output terminal 3, wherein the transformation ratio can be changed during operation by the semiconductor switching elements 14d and the electrically continuously variable reactance 16.
[0081] Fig. 3e shows a further embodiment of the second impedance matching unit 7e in L-shape, which comprises the second impedance matching unit 7d from Fig. 3d. In addition to the second impedance matching unit 7d described in the description of Fig. 3d, this second impedance matching unit 7e here comprises an additional inductance L3e, an additional semiconductor switching element 14e, additional terminals 11', 12' for an electrically continuously variable reactance, and an additional electrically continuously variable reactance 16. The inductance L3e is connected in series with the semiconductor switching element 14e. The series circuit is connected in parallel with the inductance L3d. Furthermore, the additional electrically continuously variable capacitance 16 (not shown) is connected in parallel with this series circuit and the inductance L3d. The additional electrically continuously variable reactance 16 is connected to the terminals 11', 12'.
[0082] The semiconductor switching element 14e is connected to a control circuit 15e, which is configured to switch the semiconductor switching element 14e on and off. When the semiconductor switching element 14e is switched on, the two inductors L3e, L3d and the additional electrically continuously variable reactance 16 are connected in parallel.
[0083] When the semiconductor switching element 14e is turned off, the inductance L3e has no influence on the impedance of the second impedance matching unit 7e and the second impedance matching unit 7e corresponds to the second impedance matching unit 7d of Fig. 3d, wherein the inductance L3d is connected in parallel with the additional electrically continuously variable reactance 16.
[0084] This second impedance matching unit 7e is designed to transform the intermediate impedance Zi at its input 10 to an output impedance Zp at the output terminal 3, wherein the transformation ratio can be changed during operation by the semiconductor switching elements 14d, 14e and the electrically continuously variable reactances 16.
[0085] Fig. 3f shows a further embodiment of the second impedance matching unit 7f in an L-shape, which has an inductance L3f as well as three further capacitors C3f and three semiconductor switching elements 14f. The three semiconductor switching elements 14f are designed as PIN diodes. The inductance L3f is connected between input 10 and output terminal 3. The semiconductor switching elements 14f are each connected in series with a capacitor C3f. These three series circuits are connected in parallel. An electrically continuously variable reactance 16 (not shown) is also connected in parallel to the series circuits. This entire parallel circuit can be expanded by further parallel-connected series circuits, but can also have only two parallel-connected series circuits and one electrically continuously variable reactance.Each semiconductor switching element 14f is connected to a control circuit 15f configured to switch the semiconductor switching elements 14f on and off. When one of the three semiconductor switching elements 14f is switched on, one of the three capacitors C3f is connected in parallel with the electrically continuously variable reactance 16. This parallel circuit is connected from input 10 to ground. If one or the other two semiconductor switching elements 14f are also switched on, a parallel circuit of two or three capacitors C3f and the electrically continuously variable reactance 16 is connected from input 10 to ground. When all semiconductor switching elements 14f are switched off, the capacitors C3f have no effect, and the electrically continuously variable reactance 16 is switched from input 10 to ground.
[0086] This second impedance matching unit 7f is designed to transform the first intermediate impedance Zi at its input 10 to an output impedance Zp at the output terminal 3, wherein the transformation ratio can be changed during operation by the semiconductor switching elements 14f and the electrically continuously variable reactances 16.
[0087] The previously described impedance matching units 6, 7a-7f can be varied, so that instead of capacitances, depending on the desired matching, inductances can be used, or instead of inductances, depending on the desired matching, capacitances can be used.
[0088] The previously described impedance matching units 6, 7a-7f can be used individually or in combination of two or more.
[0089] Fig. 4a to d show a selection of different embodiments of electrically continuously variable reactances 16. These electrically continuously variable reactances 16 are designed to be connected via the first and second terminals 11, 12 of the second impedance matching unit 7, 7a-7f.
[0090] Fig. 4a shows an arrangement in which the electrically continuously variable reactance 16 is connected in parallel to a parallel circuit comprising several series circuits, each consisting of a capacitor C4a and a semiconductor switching element 14. Such parallel circuits are already shown as examples in Figs. 3d and 3e.
[0091] Fig. 4b shows a possible embodiment of an electrically continuously variable reactance 16. The electrically continuously variable reactance 16 has a first terminal 11, a second terminal 12, a control terminal 13, two capacitors C4b, C4b', two inductors L4b, L4b', and a varactor Vb. The first terminal 11 is connected to the capacitor C4b. The control terminal 13 is connected to the inductor L4b'. The inductor L4b' and the capacitor C4b are further connected to each other via a node and to the cathode of the varactor Vb. The anode of the varactor Vb is connected via a node to the capacitor C4b' and the inductor L4b. The capacitor is further connected to the second terminal 12. The inductor L4b is connected to ground.
[0092] The varactor Vb can be used to vary the capacitance by changing the applied voltage.
[0093] The two capacitors C4b, C4b' and the two inductors L4b, L4b' can be used as RF blocking filters. For this purpose, the capacitors C4b, C4b' can be dimensioned such that the capacitance for the connection of the first terminal
[0094] 11 to the second terminal 12 is essentially determined only by the varactor Vb and at the same time the uniform voltage applied to the control terminal 13 does not affect the first terminal 11 or the second terminal 12. For this purpose, the two inductors L4b, L4b' can also be dimensioned such that the RF signal from the first terminal 11 to the second terminal
[0095] 12 does not affect the control, which is connected to the control terminal 13 and is only connected to ground via the inductance L4b' with very high resistance.
[0096] Fig. 4c shows largely the same embodiment of the electrically continuously variable reactance 16 from Fig. 4b. In Fig. 4c, only the varactor Vb is replaced by a transistor T. By suitable control, in particular by keeping the transistor T off, a variation of the capacitance can also be achieved via this transistor T.
[0097] Fig. 4d shows a further embodiment of the electrically continuously variable reactance 16. The electrically continuously variable reactance 16 has a first terminal 11, a second terminal 12, a control terminal 13, eight varactors Vdl-Vd8, and five inductors L4d-L4d'"'. The varactors Vdl-Vd8 are interconnected in parallel and series circuits. By interconnecting these eight varactors Vdl-Vd8 in different ways, a significantly greater possible variation in capacitance can be achieved than would be the case, for example, with a single varactor. The varactors Vdl-Vd8 have the same function as the varactor Vb in Fig. 4b and could each be replaced by a transistor T, as shown in Fig. 4c. The five inductors L4d-L4d"" have the same function as the two inductors L4b, L4b' in Fig. 4b and Fig. 4c.The two capacitances C4d, C4d' have the same function as the two capacitances C4b, C4b' in Fig. 4b and Fig. 4c.
[0098] With such an arrangement, the RF signal, which is conducted from the first terminal 11 to the second terminal 12, is distributed among the eight varactors Vdl-Vd8. This allows the electrically continuously variable reactance 16 to be operated with higher currents and higher voltages. However, it is also clear how advantageous the condition for the impedance transformation of the first impedance matching unit 6 can be used, allowing one to convert from an electrically continuously variable reactance 16 according to Fig. 4d to one according to Fig. 4b or 4c.
Claims
Claims 1. Impedance matching circuit (1) for powers > 500 W and frequencies in the range from 2 to 100 MHz, in particular for a plasma process supply system (108) and plasma process system (100), comprising: a) a first impedance matching unit (6) comprising one or more reactances (C2, C2a, L2a, C2b, C2b', L2, L2b), which is designed to carry out a first predetermined impedance transformation from its input connection (2) to its output (9), b) a second impedance matching unit (7, 7a-7f), which is designed to carry out a second predetermined impedance transformation with an adjustable transformation ratio from its input connection (10) to its output connection (3), comprising: i) one or more reactances (C3, C3a, C3a', L3a, C3b, C3b', C3d, C3d', L3d, L3e, C3f, L3f) and ii) a semiconductor switching element (14, 14a-f), wherein the transformation ratio can be changed in predetermined steps by the semiconductor switching element (14, 14a-f) during operation,and iii) an electrically continuously variable reactance (16), wherein the transformation ratio can be continuously varied during operation by the electrically continuously variable reactance (16), c) wherein the semiconductor switching element (14, 14a-f) and / or the electrically continuously variable reactance (16) can be operated up to a maximum permissible voltage and a maximum permissible current, d) wherein the first impedance matching unit (6) is designed to carry out the first predetermined impedance transformation in such a way that i) the conductance (Gi,G, P ) of the impedance (Zi, Z P) at the input or output of the second impedance matching unit (7, 7a-f) is greater than the conductance of the impedance that would be present at the input or output of the second impedance matching unit (7, 7a-f) at the rated power of the impedance matching unit and the maximum permissible voltage of the at least one semiconductor switching element (14, 14a-14f) and / or the electrically continuously variable reactance (16); and ii) the resistance (Ri,Rp) of the impedance (Zi, Z P ) at the input or output of the second impedance matching unit (7, 7a-7f) is greater than the resistance of the impedance which would be present at the input or output of the second impedance matching unit at the rated power and the maximum permissible current of the at least one semiconductor switching element (14) and / or the electrically continuously variable reactance (16).
2. Impedance matching circuit (1) according to the preceding claim 1, characterized in that the input impedance (Zo) is substantially constant and equal to the predetermined desired input impedance during operation of the impedance matching circuit (1).
3. Impedance matching circuit (1) according to the preceding claim 1, wherein the first impedance matching unit (6) is implemented as a first impedance matching unit (6) with exclusively fixed reactances.
4. Impedance matching circuit (1) according to the preceding claim 1, wherein the impedance matching circuit (1) has a plurality of semiconductor switching elements (14, 14a-f) and one, in particular a plurality of control circuit(s) (15a-f) respectively assigned to these semiconductor switching elements, wherein the semiconductor switching elements are each designed to switch reactances (C3a', C3b', C3d', C3f, L3e) on and off.
5. Impedance matching circuit (1) according to one of the preceding claims, characterized in that the at least one semiconductor switching element (14, 14a-14f) of the second impedance matching unit (7, 7a-7f) is a transistor or a diode.
6. Impedance matching circuit (1) according to one of the preceding claims, characterized in that the at least one semiconductor switching element (14, 14a-14f) of the second impedance matching unit (7, 7a-7f) can be cooled by a fluid.
7. Plasma process supply system (108) comprising an RF power supply (101) for providing the RF power signal and an impedance matching circuit (1) according to one of the preceding claims, wherein the impedance matching circuit (1) is electrically connected to the RF power supply (101) and is designed to be connected to a consumer (102), in particular a plasma process arrangement, e.g. in the form of a plasma process chamber.
8. A plasma process system (100) comprising a plasma process supply system (108) according to the preceding claim 7 and a consumer (102), in particular a plasma process arrangement, e.g., in the form of a plasma process chamber, wherein the consumer (102) is connected to the plasma process supply system (6) and the plasma process supply system (6) is configured to supply the consumer (102) with power from the RF power signal.