Impedance matching device

Abstract

This invention provides an impedance matching device that can estimate whether or not an impedance-variable element has been replaced in an unconventional manner. [Solution] When power is supplied from an external power source 60, the state is defined as the ON state, and when power is not supplied, the matching control unit 39 stores information about the electrode positions of the variable capacitors 321 and 322 as OFF position information in the storage unit 38 when the state changes from ON to OFF. After the state changes from OFF to ON, it gives command signals to the drive units 33 and 34 so that the electrode positions are in a predetermined position (structural minimum position). Based on the amount of change in the information about the positional relationship of the electrodes until the predetermined positional relationship is reached, it estimates the information about the electrode positions when the state changes from OFF to ON as ON position information, and determines whether the difference between the OFF position information and the ON position information is within a predetermined range.

Description

Technical Field

[0001] The present disclosure relates to an impedance matcher.

Background Art

[0002] For example, a high-frequency power supply system used in a plasma processing apparatus supplies high-frequency power having a fundamental frequency in the RF band (RF: Radio Frequency) from a high-frequency power source to a load (e.g., a plasma processing apparatus).

[0003] Also, an impedance matcher (sometimes referred to as an impedance matching device) is provided between the high-frequency power source and the load, and the variable value (e.g., capacitance, inductance) of an internal impedance variable element is adjusted so that the power value of the reflected wave power at the high-frequency power source side (e.g., the input end) in the impedance matcher becomes small, thereby performing an operation of matching the impedances of the high-frequency power source and the load. Thus, an operation of attempting to match the impedance by changing the variable value of the impedance variable element is referred to as a matching operation.

[0004] As disclosed in Patent Documents 1 to 3, for example, a variable capacitor (sometimes referred to as a variable condenser) and a variable inductor are used as the impedance variable element.

[0005] The variable capacitor is configured such that the positional relationship of the electrodes can be changed by driving means such as a motor, and the capacitance (capacitance) can be changed by changing the positional relationship of the electrodes. Also, the variable inductor is configured such that the positional relationship of the windings can be changed by driving means such as a motor, and the inductance can be changed by changing the positional relationship of the windings. That is, the reactance value such as the capacitance or inductance of the impedance variable element can be changed.

[0006] This allows for adjustment of the load-side impedance as seen from the high-frequency power supply side (e.g., the input terminal) to the load side in an impedance matching device.

[0007] The structure of an impedance variable element, which changes the relative positions of its electrodes or windings, is mechanical, and therefore mechanical wear occurs when these positions are changed. Consequently, it has a mechanical lifespan. When an impedance variable element reaches the end of its mechanical lifespan, it ceases to function, requiring replacement depending on its usage. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2008-251976 [Patent Document 2] Japanese Patent Publication No. 2007-158438 [Patent Document 3] Japanese Patent Publication No. 2009-010190 [Overview of the project] [Problems that the invention aims to solve]

[0009] Since there are individual differences in the reactance value of variable impedance elements, it is advisable to change the impedance matching circuit settings to match the reactance value of the replaced variable impedance element.

[0010] If the variable impedance element is replaced by the manufacturer or distributor, the impedance matching circuit's settings will be adjusted to match the reactance value of the replaced element, so there is no problem. However, if the variable impedance element is replaced by someone other than the manufacturer or distributor, the impedance matching circuit's settings will not be changed, which may lead to inaccurate matching operation during actual use or other issues such as malfunctions.

[0011] This disclosure provides an impedance matching device that can estimate whether an impedance variable element has been replaced in an unofficial manner by someone other than the manufacturer or distributor. [Means for solving the problem]

[0012] The impedance matching device according to this disclosure is an impedance matching device provided between a high-frequency power supply that supplies high-frequency power to a load and the load, comprising: a matching circuit having electrodes and windings and at least one variable impedance element in which the positional relationship of the electrodes or windings is variable; a driving means for changing the positional relationship of the electrodes or windings; a position acquisition means for acquiring information on the positional relationship of the electrodes or windings; a non-volatile storage means for storing information on the positional relationship of the electrodes or windings; a control unit; a power supply state determination means for determining whether power for operating the control unit is supplied from an external power supply source; and an auxiliary power supply that supplies power to the control unit when the power supply from the external power supply source is stopped, wherein the external power supply source When power is supplied, the state is defined as the ON state, and when power is not supplied from the external power source, the control unit stores information about the positional relationship of the electrodes or windings as OFF position information in the storage means when the state changes from the ON state to the OFF state. After the state changes from the OFF state to the ON state, the control unit gives a command signal to the drive means so that the positional relationship of the electrodes or windings becomes a predetermined positional relationship. Based on the amount of change in the information about the positional relationship of the electrodes or windings until the predetermined positional relationship is reached, the control unit estimates the information about the positional relationship of the electrodes or windings when the state changes from the OFF state to the ON state as ON position information, and determines whether the difference between the OFF position information and the ON position information is within a predetermined range. [Effects of the Invention]

[0013] According to the impedance matching device described herein, it is possible to estimate whether or not the impedance variable element has been replaced in an irregular manner. [Brief explanation of the drawing]

[0014] [Figure 1] A diagram showing an example configuration of a high-frequency power supply system. [Figure 2] A diagram showing an example of the circuit configuration of the power transmission unit 40. [Figure 3] A diagram showing other configuration examples of matching circuits. [Figure 4] A flowchart illustrating a method for estimating whether an impedance-variable element has been replaced in an unnatural manner. [Modes for carrying out the invention]

[0015] Hereinafter, an embodiment of the impedance matching device according to this disclosure will be described with reference to the drawings.

[0016] (Embodiment) Figure 1 shows an example of the configuration of a high-frequency power supply system. The high-frequency power supply system 1 is a device that outputs high-frequency power with a fundamental frequency (frequency of the fundamental wave) in the RF (RF: Radio Frequency) band from a high-frequency power supply 10 and supplies it to a load 50 (for example, a plasma processing device) via an impedance matching unit 30.

[0017] In this specification, the voltage component of high-frequency power is referred to as high-frequency voltage, and the current component of high-frequency power is referred to as high-frequency current. Furthermore, the high-frequency voltage directed from the high-frequency power supply 10 to the load 50 is defined as the forward wave voltage VF, the high-frequency voltage reflected from the load 50 and returning to the high-frequency power supply 10 is defined as the reflected wave voltage VR, the high-frequency power directed from the high-frequency power supply 10 to the load is defined as the forward wave power PF, and the high-frequency power reflected from the load and returning to the high-frequency power supply 10 is defined as the reflected wave power PR. In Figure 1, the reflected wave voltage VR and the reflected wave power PR are represented by dashed lines.

[0018] In addition, in this specification, the power value of the traveling wave power PF is defined as the traveling wave power value pf, the power value of the reflected wave power PR is defined as the reflected wave power value pr, and the power value obtained by subtracting the reflected wave power value pr from the traveling wave power value pf is defined as the load-side power value pL.

[0019] Also, in this specification, the reflection coefficient represented by the ratio of the reflected wave voltage VR to the traveling wave voltage VF (reflected wave voltage VR / traveling wave voltage VF) is defined as ρ, and the absolute value (magnitude) of the reflection coefficient ρ is defined as Γ. In practice, the reflection coefficient ρ is calculated using the traveling wave voltage detection signal vf and the reflected wave voltage detection signal vr described later, i.e., ρ = reflected wave voltage detection signal vr / traveling wave voltage detection signal vf.

[0020] Furthermore, the high-frequency power supply 10 can reduce the reflected wave power value pr by changing the frequency of the output traveling wave power PF (traveling wave voltage VF). Hereinafter, this function is referred to as "frequency matching". When the frequency matching operation is performed, the fundamental frequency of the traveling wave voltage VF is not constant but fluctuates. However, the expression "fundamental frequency" is used even when such a fundamental frequency fluctuates.

[0021] In addition, the high-frequency power supply 10 may perform frequency modulation control, for example, to reduce the reflected wave power value pr caused by intermodulation distortion (hereinafter, IMD: InterModulation Distortion). Even when frequency modulation control is performed, the fundamental frequency of the traveling wave voltage VF is not constant but fluctuates. However, the expression "fundamental frequency" is used.

[0022] The high-frequency power supply 10 performs feedback control so that the error between the traveling wave power value pf and the target power value pt decreases. Such power control is referred to as traveling wave power constant control (PF constant control). It is also possible to perform feedback control so that the error between the load-side power value pL and the target power value pt decreases. Such power control is referred to as load-side power constant control (PL constant control). However, hereinafter, the case of mainly performing traveling wave power constant control will be used as an example for explanation.

[0023] The traveling wave voltage VF has a relatively high fundamental frequency suitable for plasma generation, for example. The fundamental frequency is, for example, 40.68 MHz. Of course, the fundamental frequency is not limited to 40.68 MHz; it may be a frequency in the industrial RF band, such as 13.56 MHz or 27.12 MHz.

[0024] The traveling wave voltage VF may have a relatively low fundamental frequency suitable for ion acceleration, for example. In this case, the fundamental frequency is, for example, 400 kHz. Of course, the fundamental frequency is not limited to 400 kHz and may be other frequencies. Thus, the fundamental frequency of the traveling wave voltage VF can be various frequencies depending on the application.

[0025] As shown in Figure 1, the high-frequency power supply system 1 includes a high-frequency power supply 10 and an impedance matching unit 30. The high-frequency power supply system 1 may use multiple (for example, two) high-frequency power supplies 10. For example, it may use a first high-frequency power supply with a fundamental frequency of 40.68 MHz for the traveling wave power PF (traveling wave voltage VF) and a second high-frequency power supply with a fundamental frequency of 400 kHz for the traveling wave power PF (traveling wave voltage VF). In this case, the first high-frequency power supply supplies high-frequency power to the load 50 via the first impedance matching unit, and the second high-frequency power supply supplies high-frequency power to the load 50 via the second impedance matching unit. However, in this embodiment, as shown in Figure 1, the case where the high-frequency power supply system 1 uses a single high-frequency power supply 10 will be described as an example.

[0026] The high-frequency power supply 10 amplifies the high-frequency signal output from an oscillator (not shown) and outputs high-frequency power (forward wave power) having an output frequency in the RF band, which is supplied to the load 50. The high-frequency power output from the high-frequency power supply 10 is supplied to the load 50 via a transmission line 71, an impedance matching unit 30, and a transmission line 72. The transmission line 71 can be, for example, a coaxial cable or coaxial tube. The transmission line 72 can be, for example, a load connection member made of shielded copper plates. The length of the transmission lines 71 and 72 will vary depending on the environment and operating conditions to which the high-frequency power supply system 1 is applied.

[0027] The impedance matching device 30 matches the impedance between the high-frequency power supply 10 and the load 50. More specifically, if the impedance seen from the output terminal of the high-frequency power supply 10 towards the high-frequency power supply 10 side (output impedance) is designed to be, for example, 50Ω, and the high-frequency power supply 10 is connected to the input terminal of the impedance matching device 30 via a transmission line 71 with a characteristic impedance of 50Ω, then the impedance matching device 30 converts the impedance seen from the high-frequency power supply 10 side (for example, the input terminal) towards the load 50 side to 50Ω.

[0028] Load 50 is, for example, a plasma processing apparatus. A plasma processing apparatus is equipped with a processing section and is used to process (etch, CVD, etc.) workpieces such as wafers and liquid crystal substrates that are brought into the processing section. To process the workpiece, load 50 introduces a plasma discharge gas into the processing section and applies high-frequency power (high-frequency voltage) supplied from a high-frequency power supply 10 to the plasma discharge gas, thereby discharging the plasma discharge gas and changing it from a non-plasma state to a plasma state. The workpiece is then processed using the plasma.

[0029] <Details of Impedance Matching Device 30> The impedance matching unit 30 includes a matching unit sensor 31, a matching circuit 32, a first drive unit 33, a second drive unit 34, a first position detection unit 35, a second position detection unit 36, a load information calculation unit 37, a matching control unit 39, a power transmission unit 40, a power supply monitoring unit 41, an auxiliary power supply 42, and a storage unit 43.

[0030] Note that the input terminal 301 and output terminal 302 of the impedance matching unit 30 are usually provided with input and output terminals, but these are omitted from the illustration. Also, the housing of the impedance matching unit 30 is usually provided with an input terminal for receiving power from an external power supply source 60, but this is omitted from the illustration.

[0031] The matching sensor 31 is located at the input terminal 301 (preceding the matching circuit 32) of the impedance matching unit 30 and detects information for calculating the load-side impedance Z as seen from the high-frequency power supply 10 side (e.g., input terminal 301) to the load 50 side of the impedance matching unit 30, or information for calculating the reflection coefficient ρ on the high-frequency power supply 10 side (e.g., input terminal 301) of the impedance matching unit 30. Since the load-side impedance Z and the reflection coefficient ρ are mutually convertible, either one may be detected.

[0032] When calculating the load-side impedance Z, for example, a voltage detector and a current detector are used as the matching sensor 31. In this case, the voltage on the high-frequency power supply 10 side (e.g., input terminal) of the impedance matching unit 30 is detected by the voltage detector, and a voltage detection signal vm is output as the detection signal. In addition, the current on the high-frequency power supply 10 side (e.g., input terminal 301) of the impedance matching unit 30 is detected by the current detector, and a current detection signal im is output as the detection signal. The voltage detection signal vm and the current detection signal im are output to the load information calculation unit 37.

[0033] When calculating the reflection coefficient ρ on the high-frequency power supply 10 side (for example, the input terminal 301) of the impedance matching unit 30, a directional coupler is used as the matching unit sensor 31, for example. In this case, the forward wave voltage VF output from the high-frequency power supply 10 is detected, and a forward wave voltage detection signal vfm is output as the detection signal. At the same time, the reflected wave voltage VR that is reflected back from the load 50 side is detected, and a reflected wave voltage detection signal vrm is output as the detection signal. The forward wave voltage detection signal vfm and the reflected wave voltage detection signal vrm are output to the load information calculation unit 37.

[0034] An A / D converter (not shown) may be provided between the matching sensor 31 and the load information calculation unit 37. Furthermore, a filter for removing unwanted signal components (e.g., harmonic components) may be provided between the matching sensor 31 and the load information calculation unit 37. The filter type can be selected as appropriate.

[0035] The matching circuit 32 is provided between the matching sensor 31 and the load 50. This matching circuit 32 is equipped with an impedance variable element, such as a variable capacitor (also called a variable capacitor) whose capacitance can be changed, and the variable value of the impedance variable element (capacitance in the case of a variable capacitor, inductance in the case of a variable inductor) is changed by a command from the matching control unit 39, which will be described later, and the load side impedance Z of the impedance matching unit 30, as seen from the high-frequency power supply 10 side (for example, the input terminal) to the load 50 side, can be adjusted.

[0036] Furthermore, the impedance Z' viewed from the output terminal of the high-frequency power supply 10 towards the load 50 is approximately the same as the load-side impedance Z. Strictly speaking, the two differ depending on the length of the transmission line 71, etc., but in this embodiment, the error is considered to be within an acceptable range for practical purposes.

[0037] In some cases, a variable inductor is provided as an impedance-variable element. Furthermore, a driving means such as a motor is provided to change the variable value of the impedance-variable element according to a command from the matching control unit 39. In addition to the impedance-variable element, an inductor with a fixed inductance is often provided. Also, a capacitor with a fixed capacitance may be provided.

[0038] The matching circuit 32 shown in Figure 1 is an example of a matching circuit. The matching circuit 32 in Figure 1 includes a first variable capacitor 321 provided between the output terminal of the matching sensor 31 and ground, a second variable capacitor 322 provided between the output terminal of the matching sensor 31 and the load 50, and an inductor 323 with a fixed inductance provided between the second variable capacitor and the load 50. The capacitance of the first variable capacitor 321 will be denoted as C1, and the capacitance of the second variable capacitor 322 will be denoted as C2.

[0039] The first variable capacitor 321 and the second variable capacitor 322 are variable capacitors of a type that change capacitance by changing the relative positions of electrodes using a driving means such as a motor. For example, as described in Patent Documents 1 and 2, the electrodes of a variable capacitor are composed of a fixed electrode and a movable electrode, and the opposing area of ​​the electrodes changes when the position of the movable electrode is changed using a driving means such as a motor. Of course, variable capacitors are not limited to this type. For example, there may be a type in which the distance between electrodes changes when the position of the movable electrode is changed.

[0040] In such a first variable capacitor 321 and second variable capacitor 322, the position of the movable electrode changes by rotating a rotating shaft connected to the movable electrode using a driving means such as a motor. Therefore, the position of the movable electrode can be determined by detecting the rotation angle of the rotating shaft. The rotation angle of the rotating shaft can be detected, for example, using an encoder. In other words, the positional relationship of the electrodes can be detected by detecting the rotation angle of the rotating shaft.

[0041] The axis of rotation is designed, for example, to change the capacitance from a minimum to a maximum value in 10 rotations (3,600 degrees). However, in practice, taking into account the variation in the capacitance of the variable capacitor, it is designed to allow 10+α rotations (for example, 12 rotations), and the predetermined capacitance is achieved in 10 of those rotations.

[0042] For example, in the case of a variable capacitor with a catalog value of a minimum capacitance of 100pF and a maximum capacitance of 1,300pF, it is designed so that 10 turns result in a capacitance of 200 to 1,200pF. Therefore, the ranges of 100-200pF and 1,200-1,300pF are not used in matching operation. In other words, when matching operation is performed, 200pF becomes the minimum capacitance and 1,200pF becomes the maximum capacitance.

[0043] Therefore, when performing matching operation, the rotation angle of the rotation axis when the capacitance is 200pF is set as 0 degrees for control purposes. In practical terms, for example, the rotation angle obtained by subtracting one rotation from the rotation angle of the rotation axis when the minimum capacitance of the variable capacitor (100pF) is used is set as 0 degrees for control purposes.

[0044] Similarly, the rotation angle of the axis of rotation when the capacitance is 1,200 pF is set to 3,600 degrees for control purposes. In practical terms, for example, the rotation angle of the axis of rotation when the variable capacitor has its structurally maximum capacitance (1,300 pF) can be set to 3,600 degrees for control purposes by subtracting one rotation from the rotation angle of the axis of rotation when the capacitor has its structural maximum capacitance.

[0045] Because of this relationship, in order to set the rotation angle of the rotation axis to 0 degrees for control purposes, the rotation angle of the rotation axis should first be set to the rotation angle that results in the minimum capacitance structurally (structural 0 degrees), and then rotated to the control-oriented 0 degrees. Note that when the rotation axis is rotated so that the capacitance is the minimum capacitance, the rotation will structurally stop when it reaches the rotation angle corresponding to the minimum capacitance. Therefore, this rotation angle is considered to be the structural 0 degrees.

[0046] Furthermore, to set the rotation angle of the rotating shaft to a controllable 3,600 degrees, the rotation angle of the rotating shaft should first be set to the rotation angle corresponding to the structurally maximum capacitance, and then the rotation angle obtained by subtracting 1 rotation should be set to the controllable 3,600 degrees. Note that when the rotating shaft is rotated to achieve the maximum capacitance, the rotation will structurally stop when it reaches the rotation angle corresponding to the maximum capacitance. Therefore, this rotation angle is set to the structurally maximum rotation angle.

[0047] This allows the capacitance of the variable capacitor to be changed within a predetermined range. This operation is performed after the variable capacitor is initially installed or after it has been replaced. By performing this operation, the relationship between the structural rotation angle of the variable capacitor's rotation axis and the control rotation angle can be set.

[0048] Note that it is sufficient to know either 0 degrees or 3,600 degrees for control purposes. Therefore, in this embodiment, the following explanation will proceed assuming that 0 degrees for control purposes is set.

[0049] The first drive unit 33 changes the position of the movable electrode of the first variable capacitor 321. The second drive unit 34 changes the position of the movable electrode of the second variable capacitor 322. Such a first drive unit 33 and second drive unit 34 are examples of the drive means of the present invention.

[0050] The first drive unit 33 and the second drive unit 34 each consist of a motor and a driver for driving that motor. The output shaft of the motor is connected to the rotating shaft of the variable capacitor, so that when the output shaft of the motor rotates, the rotating shaft of the variable capacitor rotates, and the position of the movable electrode changes as a result of this rotation.

[0051] The motor is, for example, a stepping motor. Of course, it is also possible to use other types of motors (such as servo motors), but in this embodiment, we will describe the case in which a stepping motor is used.

[0052] Here, a stepping motor is a motor that rotates by moving in fixed increments of angle. The corresponding driver receives pulse signals output from the control unit as command signals and operates the stepping motor based on these command signals. When using a stepping motor in this way, it is easiest to represent the position of the movable electrode with the number of steps corresponding to the number of pulse signals supplied to the stepping motor. For example, if the rotation angle of the rotation axis rotates from 0 to 3,600 degrees (10 rotations), and the stepping motor needs to be changed by 1,000 steps, the position of the movable electrode can be represented by 0 to 1,000 steps.

[0053] The first position detection unit 35 detects the rotation angle of the first drive unit 33 and is configured to include, for example, an encoder. The detected rotation angle is output to the matching control unit 39 as rotation angle information Dc1. Similarly, the second position detection unit 36 ​​detects the rotation angle of the second drive unit 34 and is configured to include, for example, an encoder. The detected rotation angle is output to the matching control unit 39 as rotation angle information Dc2. Such first position detection unit 35 and second position detection unit 36 ​​are examples of position acquisition means of the present invention.

[0054] As described above, the rotation angles of the first drive unit 33 and the second drive unit 34 indirectly represent the position of the movable electrode of the variable capacitor. Therefore, by detecting the rotation angle of the first drive unit 33, the position of the movable electrode of the variable capacitor can be detected. As described above, when using a stepping motor, the position of the movable electrode of the variable capacitor may be managed by the number of steps.

[0055] For example, when the rotation angle of the rotation axis is 0 degrees for control purposes, the capacitance is at its minimum for control purposes, so the position of the movable electrode of the variable capacitor at this time can be set to step 0. Also, when the rotation angle of the rotation axis is 3,600 degrees for control purposes, the capacitance is at its maximum for control purposes, so the position of the movable electrode of the variable capacitor at this time can be set to step 1,000. Of course, the 0 to 1,000 steps exemplified above are just examples, and a configuration with, for example, 0 to 5,000 steps could also be used.

[0056] Furthermore, as can be seen from the above, the position of the movable electrode, the rotation angle of the variable capacitor's rotation axis, and the rotation angle of the motor all correspond to the capacitance of the variable capacitor. Therefore, by detecting any of these, the capacitance of the variable capacitor can be estimated.

[0057] In this embodiment, as an example, the capacitance of the variable capacitor is estimated based on the rotation angle of the motor. The rotation angle of the motor can be expressed in terms of steps. Therefore, if the minimum capacitance for control is set to 0 steps and the maximum capacitance to 1,000 steps, the capacitance of the variable capacitor can be expressed in terms of steps, such as 0 to 1,000 steps.

[0058] Furthermore, in the above example, the structural minimum capacitance is the capacitance at a rotation angle obtained by rotating the motor +1 from a control-defined rotation angle of 0 degrees, which corresponds to -100 steps in the control. Similarly, the structural maximum capacitance is the capacitance at a rotation angle obtained by rotating the motor +1 from a control-defined rotation angle of 3,600 degrees, which corresponds to 1,100 steps in the control.

[0059] The load information calculation unit 37 can calculate the reflection coefficient ρ or the load-side impedance Z based on the detection signal output from the matching sensor 31. When this information is used as load information IFL, the load information calculation unit 37 can output the load information IFL to the matching control unit 39. It is not necessary to calculate all of the load information IFL. For example, if the load-side impedance Z is not used for control, it does not need to be calculated.

[0060] Furthermore, the load information calculation unit 37 can calculate and output the forward wave power value pf, reflected wave power value pr, load-side power value pL, and absolute reflection coefficient Γ based on the detection signal output from the matching unit sensor 31. This information related to high-frequency power is necessary for output control of the high-frequency power supply 10, but it can also be output externally as monitoring information, for example.

[0061] Furthermore, the above-mentioned information related to high-frequency power can be used to control the impedance matcher 30. For example, the impedance matcher 30 may be configured to start matching operation when the forward wave power value pf exceeds a predetermined threshold. Of course, it may also be configured to start matching operation based on other signals (e.g., forward wave voltage detection signal vfm, reflected wave voltage detection signal vrm, etc.). Note that it is not necessary to calculate all of the above-mentioned information related to high-frequency power. For example, if the load-side power value pL is not used for control, it is not necessary to calculate the load-side power value pL.

[0062] The method for calculating the information shown above is publicly known, so a detailed explanation will be omitted, but for example, it can be calculated as follows.

[0063] (1) Reflectance coefficient ρ The reflection coefficient ρ can be calculated, for example, using the reflected wave voltage detection signal vr / forward wave voltage detection signal vf. The absolute value (magnitude) of the reflection coefficient ρ is denoted as the absolute reflection coefficient Γ.

[0064] (2) Load side impedance Z The load impedance Z can be calculated, for example, from the voltage detection signal vm and the current detection signal im. Alternatively, the load impedance Z can be calculated based, for example, on the magnitude of the voltage detection signal vm, the magnitude of the current detection signal im, and the phase difference θm between the voltage detection signal vm and the current detection signal im.

[0065] Note that the reflection coefficient ρ and the load-side impedance Z are mutually convertible. Therefore, in the following, we may explain only the reflection coefficient ρ or the load-side impedance Z.

[0066] (3) Power value of the traveling wave pf The forward wave power value pf can be calculated, for example, using the forward wave voltage detection signal vfm^2 / R (where R is the gain equivalent to the resistance value).

[0067] (4) Reflected wave power value pr The reflected wave power value pr can be calculated, for example, using the reflected wave voltage detection signal vrm^2 / R (where R is the gain equivalent to the resistance value).

[0068] (5) Load-side power value pL The load-side power value pL can be calculated based on the forward wave power value pf and the reflected wave power value pr calculated above. For example, the load-side power value pL can be calculated by subtracting the reflected wave power value pr from the forward wave power value pf.

[0069] (6) Absolute value of the reflection coefficient Γ The absolute value of the reflection coefficient Γ may be calculated based on the forward wave power value pf and the reflected wave power value pr. For example, the absolute value of the reflection coefficient Γ may be calculated by √(reflected wave power value pr / forward wave power value pf).

[0070] The matching control unit 39 performs matching operations using the load information IFL output from the load information calculation unit 37, the rotation angle information Dc1 output from the first position detection unit 35, and the rotation angle information Dc2 output from the second position detection unit 36.

[0071] For example, the matching circuit 32 outputs command signals Sc1 and Sc2 to change the capacitance C1 of the first variable capacitor 321 and the capacitance C2 of the second variable capacitor 322 so that the absolute value of the reflection coefficient Γ approaches the target absolute value of the reflection coefficient Γ0 (usually 0).

[0072] In other words, command signals Sc1 and Sc2 are output to change the capacitance C1 of the first variable capacitor 321 and the capacitance C2 of the second variable capacitor 322 so that the reflected wave power is reduced.

[0073] The first drive unit 33 and the second drive unit 34 rotate the rotation axes of the first variable capacitor 321 and the second variable capacitor 322 based on command signals Sc1 and Sc2 output from the matching control unit 39. By repeating this operation, the absolute value Γ approaches the target reflection coefficient absolute value Γ0 (usually 0). In other words, the reflected wave power decreases. Matching operation is performed by performing this operation.

[0074] There are various methods for matching the operation. For example, the capacitance C1 of the first variable capacitor 321 and the capacitance C2 of the second variable capacitor 322 can be calculated, and command signals Sc1 and Sc2 can be output to the first drive unit 33 and the second drive unit 34, using these capacitances as targets.

[0075] Even when performing such matching operations, there are various ways in which the command signals Sc1 and Sc2 are output. For example, if the difference between the current capacitance and the target capacitance is large, the capacitance between the two may be used as the target capacitance. Although various other methods have been disclosed, the method of matching operation is not limited in this embodiment.

[0076] In any case, the absolute value of the reflection coefficient Γ is controlled to approach the target absolute value of the reflection coefficient Γ0 (usually 0), in other words, the reflected wave power is controlled to be small.

[0077] Furthermore, the matching control unit 39 can monitor whether or not power is being supplied from the external power supply source 60, which will be described later. For example, if the state in which power is being supplied from the external power supply source 60 is defined as the ON state, and the state in which power is not being supplied from the external power supply source 60 is defined as the OFF state, the matching control unit 39 can determine that it is in the ON state when it is running. In addition, the matching control unit 39 can estimate whether or not the impedance variable element has been replaced in an irregular manner. This will be described later.

[0078] Figure 2 shows an example of the circuit configuration of the power transmission unit 40. The power transmission unit 40 transmits power supplied from an external power source 60 to the control unit. This power transmission unit 40 is located between the external power source 60 and the matching control unit 39. The power transmission unit 40 includes a resistor 401, a contact part 402, a coil 403, a resistor 404, a capacitor 405, and a diode 406. The resistor 401 is a resistor for limiting inrush current. The part consisting of the contact part 402 and the coil 403 functions as a relay circuit 407. The part consisting of the resistor 404 and the capacitor 405 functions as a delay circuit 408. The delay circuit 408 is an example of an auxiliary power supply of the present invention.

[0079] In the case of the power transmission unit 40 as shown in Figure 2, when power is supplied from an external power source 60, current flows through the coil 403, causing the contact portion 402 of the relay circuit 407 to connect, and power is transmitted from the external power source 60 to the matching control unit 39. Conversely, when power is no longer supplied from the external power source 60, the contact portion 402 of the relay circuit 407 becomes disconnected, and power is no longer transmitted from the external power source 60 to the matching control unit 39.

[0080] Furthermore, when power is supplied from the external power source 60, the capacitor 405 is charged. On the other hand, when power is no longer supplied from the external power source 60, the capacitor 405 discharges, causing current to flow through the coil 403. This current gradually decreases due to the characteristics of the delay circuit 408, which delays the timing at which the contact portion 402 of the relay circuit 407 becomes disconnected. As a result, even if the power supply from the external power source 60 is stopped, the matching control unit 39 can store information about the positional relationship of the electrodes or windings of the impedance variable element in the memory unit 43, which will be described later.

[0081] If the external power supply 60 is an AC power source, an AC-DC converter may be provided at the input or output terminal of the power transmission unit 40, but this is omitted from the illustration in Figures 1 and 2. Furthermore, the power transmission unit 40 does not necessarily need to include a relay circuit 407 or a delay circuit 408 as shown in Figure 2. For example, if the external power supply 60 is an AC power source, an AC-DC converter without a relay circuit 407 or delay circuit 408 may be used as the power transmission unit 40. In addition, a DC-DC converter may be provided as needed. Also, if the external power supply 60 is a DC power source, a DC-DC converter may be used as the power transmission unit 40. Thus, the power transmission unit 40 only needs to transmit power supplied from the external power supply 60 to the control unit. However, since the delay circuit 408 functions as an auxiliary power supply, if the delay circuit 408 is not provided, an auxiliary power supply 42, which will be described later, must be provided.

[0082] The power supply monitoring unit 41 monitors whether or not power is being supplied from the external power source 60 by monitoring the voltage at the input terminal of the power transmission unit 40 (the output terminal of the external power source 60). The power supply monitoring unit 41 is an example of the power supply status determination means of the present invention.

[0083] When power is supplied from the external power source 60, the voltage at the input terminal of the power transmission unit 40 becomes higher than a preset OFF threshold (for example, a threshold of 3V for DC 5V), indicating that power is being supplied from the external power source 60. On the other hand, when power is not being supplied from the external power source 60, the voltage at the input terminal of the power transmission unit 40 becomes below the preset OFF threshold, indicating that power is not being supplied from the external power source 60. Here, the state in which power is being supplied from the external power source 60 is defined as the ON state, and the state in which power is not being supplied from the external power source 60 is defined as the OFF state.

[0084] The power supply monitoring unit 41 outputs the above-mentioned discrimination result Dp to the matching control unit 39. The discrimination result Dp is, for example, 1 if the state is ON, and for example, 0 if the state is OFF. In this way, by monitoring the voltage at the input terminal of the power transmission unit 40 (the output terminal of the external power supply source 60), it is possible to instantly determine whether or not power is being supplied from the external power supply source 60.

[0085] As mentioned above, the matching control unit 39 also monitors whether or not power is being supplied from the external power supply source 60, but it is desirable to instantly determine when the state has changed from ON to OFF. Therefore, it is desirable to determine when the state has changed from ON to OFF based on the determination result Dp of the power supply monitoring unit 41.

[0086] This is because, as will be explained later, the matching control unit 39 needs to store the position information of the movable electrode and winding of the impedance variable element in the storage unit 43 while it is still operational, when the impedance variable element changes from the ON state to the OFF state. However, when using the power transmission unit 40 shown in Figure 2, power is supplied to the matching control unit 39 even when it is in the OFF state, so the matching control unit 39 cannot make instantaneous determination.

[0087] The auxiliary power supply 42 is for supplying power to the matching control unit 39 when power is not supplied from the external power supply source 60. For example, it may be a commercially available battery or a power supply that charges a capacitor.

[0088] Even if the power supply from the external power source 60 is stopped, power is supplied to the matching control unit 39 from the auxiliary power supply 42, so the matching control unit 39 can store information about the positional relationship of the electrodes or windings of the impedance variable element in the memory unit 43, which will be described later.

[0089] The memory unit 43 is a storage means equipped with non-volatile memory, and can retain stored data even when power is not supplied, such as with an EEPROM. Note that the memory unit 43 is an example of a storage means of the present invention.

[0090] The matching control unit 39 can store position information of the movable electrodes and windings of the variable impedance element in the memory unit 43. The matching control unit 39 can also read the position information stored in the memory unit 43. Furthermore, as described above, the position information of the movable electrodes and windings of the variable impedance element can be used as values ​​converted to the number of steps (for example, 0 to 1,000 steps). The impedance matcher 30 is also equipped with a volatile memory (not shown) that can store information for temporary use. Note that the matching circuit is not limited to the configuration shown in Figure 1.

[0091] Figure 3 shows another example of a matching circuit configuration. The matching circuit 32a in Figure 3 includes a first variable inductor 324 provided at the output terminal of the matching sensor 31, a second variable inductor 325 provided between the output terminal of the first variable inductor 324 and the load 50, and a capacitor 326 provided between the output terminal of the first variable inductor 324 and ground. The inductance of the first variable inductor 324 is denoted by L1, and the inductance of the second variable inductor 325 is denoted by L2. The capacitance of the capacitor 326 is a fixed value. Thus, it is also possible to use a variable inductor as an impedance-variable element. In addition, although Figure 3 shows an example using a capacitor 326 with a fixed capacitance, a variable capacitor may be used instead of capacitor 326.

[0092] A variable inductor, for example, has a fixed winding and a movable winding, and its inductance can be changed by changing the positional relationship of the movable winding relative to the fixed winding. For example, a rotating shaft is connected to the movable winding, and when this rotating shaft is rotated by a driving means such as a motor, the positional relationship of the movable winding relative to the fixed winding changes, and the inductance changes. In other words, although there is a difference between capacitance and inductance, similar to a variable capacitor, the inductance, which is the object of control, can be changed by changing the positional relationship of the windings by a driving means such as a motor.

[0093] Therefore, as shown in Figure 3, the inductance L1 of the first variable inductor 324 can be detected by changing the relative position of the windings of the first variable inductor 324 using the first drive unit 33a and by detecting the rotation angle of the motor of the first drive unit 33a using the first position detection unit 35a. The detected rotation angle is output to the matching control unit 39 as rotation angle information DL1.

[0094] Similarly, the inductance L2 of the second variable inductor 325 can be detected by changing the relative position of the windings of the second variable inductor 325 using the second drive unit 34a and by detecting the rotation angle of the motor of the second drive unit 34a using the first position detection unit 36a. The detected rotation angle is output to the matching control unit 39 as rotation angle information DL2. The first drive unit 33a, the second drive unit 34a, the first position detection unit 35a, and the second position detection unit 36a have different controlled objects, but their configurations are the same as the first drive unit 33, the second drive unit 34, the first position detection unit 35, and the second position detection unit 36 ​​shown in Figure 1, respectively. Therefore, their explanation is omitted.

[0095] Furthermore, similar to variable capacitors, the position of the movable winding, the rotation angle of the variable inductor's axis, and the rotation angle of the motor all correspond to the inductance of the variable inductor. Therefore, by detecting any of these, the inductance of the variable inductor can be estimated. Thus, similar to variable capacitors, the inductance of a variable inductor can be expressed in terms of steps, for example, 0 to 1,000 steps. Although the rotation angle of the axis differs between variable inductors and variable capacitors, the concepts of structural minimum inductance and controllable minimum inductance are the same as those for variable capacitors.

[0096] In Figure 1, an example is shown where there are two variable capacitors in the matching circuit 32, but the number of variable capacitors is not limited. For example, there may be one variable capacitor, or there may be three or more variable capacitors. Similarly, in Figure 3, an example is shown where there are two variable inductors in the matching circuit 32, but the number of variable inductors is not limited. For example, there may be one variable inductor, or there may be three or more variable inductors. Although not shown in the illustration, the matching circuit 32 may also contain a mixture of one or more variable capacitors and one or more variable inductors.

[0097] Next, we will explain a method for estimating whether or not the impedance variable element was replaced in an unconventional manner.

[0098] Figure 4 is a flowchart illustrating a method for estimating whether or not an impedance variable element has been replaced in an unnatural manner. The impedance variable element can be either a variable capacitor or a variable inductor. In the flowchart, the state where power is supplied from an external power source 60 is considered the ON state, and the state where power is not supplied from the external power source 60 is considered the OFF state.

[0099] <step1> When the matching control unit 39 changes from the ON state to the OFF state, it stores information about the positional relationship of the electrodes or windings of the impedance variable element as OFF position information in the storage unit 43.

[0100] Furthermore, whether or not the state has changed from ON to OFF can be determined based on the determination result Dp output from the power supply monitoring unit 41. In addition, information on the positional relationship of the electrodes or windings of the impedance variable element can be obtained based on the rotation angle information output from the position detection unit corresponding to the impedance variable element.

[0101] Furthermore, in the case where the impedance variable element is a variable capacitor as shown in Figure 1 (first variable capacitor 321, second variable capacitor 322), the information regarding the positional relationship of the electrodes of the impedance variable element represents the position of the movable electrode, the rotation angle of the rotation axis of the variable capacitor, or the rotation angle of the motor.

[0102] Furthermore, in the case where the impedance variable element is a variable inductor as shown in Figure 3 (first variable inductor 324, second variable inductor 325), the information regarding the positional relationship of the windings of the impedance variable element refers to the position of the movable winding, the rotation angle of the rotation axis of the variable inductor, or the rotation angle of the motor.

[0103] If there are multiple variable capacitors (in Figure 1, there are two: the first variable capacitor 321 and the second variable capacitor 322), the positional relationship information of the electrodes of each impedance variable element is stored in the storage unit 43 as OFF position information.

[0104] If there are multiple variable inductors (in Figure 3, there are two: the first variable inductor 324 and the second variable inductor 325), the relative positional information of the windings of each impedance variable element is stored in the storage unit 43 as OFF position information.

[0105] If the matching circuit 32 contains one or more variable capacitors and one or more variable inductors, the positional relationship information of the electrodes or windings of each impedance variable element is stored in the storage unit 43 as OFF position information.

[0106] <step2> After changing from the OFF state to the ON state, a command signal is sent to the drive unit corresponding to the variable impedance element so that the positional relationship of the electrodes or windings of the variable impedance element becomes a predetermined positional relationship. If there are multiple variable impedance elements, this should be done for each variable impedance element.

[0107] Furthermore, in the case where the impedance variable element is a variable capacitor, the predetermined positional relationship is either the positional relationship where the capacitance of the variable capacitor is the structural minimum capacitance, or the positional relationship where the capacitance of the variable capacitor is the structural maximum capacitance. Similarly, in the case where the impedance variable element is a variable inductor, the predetermined positional relationship is either the positional relationship where the inductance of the variable inductor is the structural minimum inductance, or the positional relationship where the inductance of the variable inductor is the structural maximum inductance.

[0108] <step3> Based on the amount of change in the positional relationship information of the electrodes or windings of the impedance variable element until it changes to the predetermined positional relationship described above, the positional relationship information of the electrodes or windings of the impedance variable element when it changes from the OFF state to the ON state is estimated as the ON position information.

[0109] For example, if the impedance variable element is the first variable capacitor 321, and the predetermined positional relationship in Step 2 is such that the structural minimum capacitance is achieved, the motor of the first drive unit 33 is rotated so that the movable electrode of the first variable capacitor 321 achieves the structural minimum capacitance.

[0110] At this time, let's assume that the position of the movable electrode of the first variable capacitor 321 when it changes from the OFF state to the ON state corresponds to a position of 500 steps in terms of control, and that the difference in the positional relationship between the structural minimum capacitance and the control minimum capacitance is 100 steps. In this case, the position of the movable electrode will change by 600 steps. Therefore, it can be seen that the ON position information corresponds to a position of 500 steps.

[0111] <step4> The system determines whether the difference between the OFF position information and the ON position information falls within a predetermined range. For example, if the predetermined range is ±10 steps, and the OFF position information for Step 1 is 500 steps, and the ON position information for Step 3 is 500 steps, then the difference between the OFF position information and the ON position information is 0. However, if the ON position information for Step 3 is 450 steps, it falls outside the predetermined range, meaning that the movable electrode or movable winding of the impedance variable element moved while the device was in the OFF state. Thus, if the difference between the OFF position information and the ON position information falls outside the predetermined range, it can be inferred that there is a high probability that the impedance variable element was removed from the impedance matcher and replaced when power for the impedance matcher to operate was not being supplied.

[0112] Because there are individual differences in the reactance value of variable impedance elements, if you replace a variable impedance element, you need to change the settings of the impedance matcher to match the reactance value of that variable impedance element.

[0113] If the variable impedance element is replaced by the manufacturer or distributor, the impedance matching circuit's settings will be adjusted to match the capacitance of the replaced element, so there is no problem. However, if the variable impedance element is replaced by someone other than the manufacturer or distributor, the impedance matching circuit's settings will not be changed, which may result in inaccurate matching during actual operation.

[0114] Therefore, if the difference between the OFF position information stored in the memory means and the estimated ON position information is not within a predetermined range, measures can be taken, for example, to prevent the impedance matching device from operating, considering the possibility that it may not be able to operate properly. Alternatively, an alarm can be output. Thus, in the impedance matching device of this embodiment, for example, if the impedance variable element is replaced illegally by someone other than the manufacturer or distributor, it is possible to prevent the device from being able to perform accurate matching operation during actual operation, or to output an alarm to warn the user. In addition, the matching control unit 39 can store information regarding the difference between the OFF position information and the ON position information in the memory unit 43.

[0115] The information to be memorized is, for example, the following information (1) to (3). (1) The difference between the OFF position information and the ON position information for each impedance variable element (e.g., the number of steps in the difference) (2) The result of determining whether the difference between the OFF position information and the ON position information for each impedance variable element was within a predetermined range (for example, "normal" if within the range, and "abnormal" if outside the range). (3) The date and time of the determination in (2) above (If this information is to be stored, the impedance matching device should be equipped with a clock function.)

[0116] In this way, by referring to the information stored in the memory unit 43, it is possible to estimate whether or not the impedance variable element has been replaced by someone other than the manufacturer or distributor. This is because, if the impedance variable element has been replaced by the manufacturer or distributor, even if the stored information indicates that the difference between the OFF position information and the ON position information is outside the predetermined range, it can be determined that the replacement was legitimate. In that case, the abnormality can be cleared.

[0117] Alternatively, instead of storing all of the above information (1) to (3) in the storage unit 43, some of the above information (1) to (3) may be stored in the storage unit 43. For example, only the information in (2) may be stored in the storage unit 43. Also, the information may be stored in the storage unit 43 only if the difference between the OFF position information and the ON position information is not within a predetermined range. Furthermore, instead of storing information for each impedance variable element, the storage unit 43 may be stored only if the difference between the OFF position information and the ON position information for any of the impedance variable elements is not within a predetermined range.

[0118] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of symbols]

[0119] 1. High-frequency power supply system 10 High frequency power supply 31 Sensor for matching unit 32 Matching circuit 33 First drive unit 34 Second drive unit 35 First position detection unit 36 Second position detection unit 37 Load Information Calculation Unit 39 Control unit for matching unit 40 Power transmission section 41 Power supply monitoring section 42 Auxiliary power supply 43 Storage section 30 Impedance Matching Devices 50 Load (Plasma Processing Equipment) 60 Power supply source

Claims

1. An impedance matching device provided between a high-frequency power supply that supplies high-frequency power to a load and the load, A matching circuit comprising at least one impedance-variable element having electrodes and windings, wherein the relative position of the electrodes or windings is variable, A driving means for changing the positional relationship of the electrode or the winding, A position acquisition means for acquiring information on the positional relationship of the electrode or the winding, A non-volatile storage means for storing information about the positional relationship of the electrodes or the windings, Control unit and A power supply state determination means for determining whether or not power for operating the control unit is being supplied from an external power source, When the power supply from the external power source is stopped, an auxiliary power supply is provided to supply power to the control unit, Equipped with, When the state in which power is supplied from the external power source is defined as the ON state, and the state in which power is not supplied from the external power source is defined as the OFF state, The control unit, When the state changes from the ON state to the OFF state, the positional relationship information of the electrode or the winding is stored in the storage means as OFF position information. After changing from the OFF state to the ON state, a command signal is given to the driving means so that the positional relationship of the electrode or the winding becomes a predetermined positional relationship. Based on the amount of change in the positional relationship information of the electrode or winding until it changes to the predetermined positional relationship, the positional relationship information of the electrode or winding when it changes from the OFF state to the ON state is estimated as the ON position information. It is determined whether the difference between the OFF position information and the ON position information falls within a predetermined range. Impedance matching device.

2. If the matching circuit is equipped with multiple impedance variable elements, it is determined whether the difference between the OFF position information and the ON position information for each impedance variable element is within the predetermined range. The impedance matching device according to claim 1.

3. The power supply state determination means determines that power is not being supplied when the voltage at the operating power input terminal connected to an external power supply source is below an OFF determination threshold, and sets the device to the OFF state. The impedance matching device according to claim 1.

4. The control unit sets itself to the ON state when it determines that power is being supplied while it is running. The impedance matching device according to claim 1.

5. It further includes a relay circuit and a delay circuit provided between an external power supply and the control unit, The aforementioned relay circuit is When the ON state is activated, current is passed through the coil, causing the contact portion to operate so that it connects the external power supply source and the control unit. The aforementioned delay circuit is When the state changes from the ON state to the OFF state, current is supplied to the coil, thereby delaying the timing at which the contact portion changes from a connected state to a disconnected state between the external power supply source and the control unit, and supplying power to the control unit via the contact portion. The impedance matching device according to claim 1.

6. The control unit, If the difference between the OFF position information and the ON position information is not within the predetermined range, The aforementioned storage means stores information that it was not within the range. An impedance matching device according to any one of claims 1 to 5.

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