High-frequency power supply system

Abstract

This invention provides a high-frequency power supply system that eliminates the problem of discrepancies in information calculated based on information detected by dedicated sensors for the high-frequency power supply and impedance matching unit. [Solution] The system includes a high-frequency power output unit 10 that outputs high-frequency power, a common sensor 14 located on the load side of the high-frequency power output unit, a power control unit 13 that acquires information related to high-frequency power calculated based on the information detected by the common sensor 14 and controls the power value of the high-frequency power, drive units 33 and 34 for changing the variable values ​​of impedance variable elements 321 and 322 in the matching circuit 32, and a matching control unit 39 that acquires the reflection coefficient ρ or load-side impedance Z calculated based on the information detected by the common sensor 14 and provides a command signal to the drive unit to change the variable values ​​of the impedance variable elements 321 and 322 so that the reflected wave power becomes smaller.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a high-frequency power supply system.

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 (for example, a plasma processing apparatus).

[0003] Further, an impedance matcher (sometimes referred to as an impedance matching device) is provided between the high-frequency power source and the load, and by adjusting the variable value (for example, capacitance, inductance) of an internal variable impedance element so that the power value of the reflected wave power on the high-frequency power source side (for example, the input end) of the impedance matcher becomes small, an operation of matching the impedance between the high-frequency power source and the load is performed. In this way, the operation of changing the variable value of the variable impedance element to achieve impedance matching is referred to as a matching operation.

[0004] The above high-frequency power source and impedance matcher are each provided with a dedicated sensor, and perform control based on information detected by each sensor.

[0005] The sensor used in the high-frequency power source is disposed at the output end of the high-frequency power source, and the sensor used in the impedance matcher is disposed on the high-frequency power source side (for example, the input end) in the impedance matcher. Therefore, the respective sensors are physically arranged at different positions via a transmission line.

[0006] The high-frequency power source calculates information related to the high-frequency power output from the high-frequency power source based on the information detected by the sensor provided at its output end, and controls the power value of the high-frequency power output from the high-frequency power source using the calculated information related to the power value.

[0007] Furthermore, the impedance matching device calculates the reflection coefficient or load-side impedance based on information detected by a sensor installed on the high-frequency power supply side (for example, its input terminal) and uses this load information to provide a command signal to the driving means to change the positional relationship of the electrodes or windings of the impedance variable element so that the reflected wave power is reduced, thereby performing the matching operation. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2024-095370 [Patent Document 2] Japanese Patent Application Publication No. 5-63604 [Patent Document 3] Japanese Patent Publication No. 2006-166412 [Overview of the project] [Problems that the invention aims to solve]

[0009] As described above, the high-frequency power supply and impedance matching unit are each equipped with dedicated sensors, and control is performed based on the information detected by these sensors. However, there may be slight differences in the impedance seen from each sensor towards the load side (hereinafter referred to as load-side impedance).

[0010] This is because the fundamental frequency of the high-frequency power output from a high-frequency power supply is high, and its wavelength is short. Therefore, even if the transmission line connecting the high-frequency power supply and the impedance matching circuit is relatively short, it will affect the load-side impedance according to its length. Furthermore, the harmonic components generated when plasma is produced in the load also affect the information detected by each sensor.

[0011] As a result, there is a possibility that differences may occur between sensors in the information calculated using the information detected by each sensor (e.g., power value, reflection coefficient). However, since the high-frequency power supply and the impedance matching circuit control different entities, even if such differences occur, there are no control problems.

[0012] On the other hand, for purposes such as analyzing the operating status of a high-frequency power supply system, it is sometimes necessary to monitor information calculated using data detected by each sensor (e.g., power value, reflection coefficient). In such cases, if there are discrepancies in the information calculated based on the data detected by each sensor (e.g., power value, reflection coefficient), it may become confusing as it becomes unclear which information to use.

[0013] To improve this problem, some attempts are made to reduce the effects of the above-mentioned differences by adjusting the length of the transmission line (coaxial cable, etc.) connecting the high-frequency power supply and the impedance matcher. However, this adjustment work requires connecting the high-frequency power supply and the impedance matcher using a transmission line (coaxial cable, etc.) and with a load connected downstream of the impedance matcher, so it requires a lot of work.

[0014] This disclosure provides a high-frequency power supply system that can suppress the occurrence of a problem in which discrepancies occur in the information calculated based on information detected by dedicated sensors for the high-frequency power supply and impedance matching device. [Means for solving the problem]

[0015] The high-frequency power supply system according to this disclosure is a high-frequency power supply system that supplies high-frequency power to a load, comprising: a high-frequency power output unit that outputs high-frequency power amplified from a high-frequency signal; a sensor provided on the load side of the high-frequency power output unit; a power control unit that acquires information related to high-frequency power calculated based on information detected by the sensor and controls the power value of the high-frequency power output from the high-frequency power supply using the acquired information; a matching circuit having electrodes and windings and comprising at least one impedance variable 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; and a matching control unit that acquires a reflection coefficient or load-side impedance calculated based on information detected by the sensor and provides a command signal to the driving means for changing the positional relationship of the electrodes or windings so that the reflected wave power is reduced using the acquired reflection coefficient or load-side impedance. [Effects of the Invention]

[0016] According to the high-frequency power supply system described herein, since a common sensor is used in both the high-frequency power supply and the impedance matching circuit, it is possible to suppress the problem of discrepancies in information (e.g., power value, reflection coefficient) calculated based on information detected by dedicated sensors installed in each of the high-frequency power supply and impedance matching circuit, as is the case in conventional systems.

[0017] Furthermore, since only one sensor is needed instead of the high-frequency power supply and impedance matching unit that were previously required separately, the installation space for the sensor can be reduced, and costs can be lowered. [Brief explanation of the drawing]

[0018] [Figure 1] A diagram showing an example configuration of a high-frequency power supply system. [Figure 2] A diagram showing another example configuration of a high-frequency power supply system. [Figure 3] A diagram showing other configuration examples of matching circuits. [Description of Embodiments]

[0019] Hereinafter, embodiments of the high-frequency power supply system according to the present disclosure will be described with reference to the drawings.

[0020] (Embodiment) Figure 1 is a diagram showing a configuration example of a high-frequency power supply system. The high-frequency power supply system 1 is an apparatus that outputs high-frequency power whose fundamental frequency (frequency of the fundamental wave) falls within the RF (Radio Frequency) band from a high-frequency power source 10, and supplies the high-frequency power to a load 50 (for example, a plasma processing apparatus) via an impedance matcher 30.

[0021] Note that in the present 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. Further, a high-frequency voltage traveling from the high-frequency power source 10 toward the load 50 is defined as traveling wave voltage VF, a high-frequency voltage reflected from the load 50 side and returning to the high-frequency power source 10 is defined as reflected wave voltage VR, high-frequency power traveling from the high-frequency power source 10 toward the load is defined as traveling wave power PF, and high-frequency power reflected from the load side and returning to the high-frequency power source 10 is defined as reflected wave power PR. In Figure 1, the reflected wave voltage VR and the reflected wave power PR are represented by broken lines.

[0022] Further, in the present specification, the power value of the traveling wave power PF is defined as traveling wave power value pf, the power value of the reflected wave power PR is defined as 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 load-side power value pL.

[0023] Further, in the present 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 as reflected wave voltage detection signal vr / traveling wave voltage detection signal vf, using the traveling wave voltage detection signal vf and the reflected wave voltage detection signal vr which will be described later.

[0024] Furthermore, the high-frequency power supply 10 can reduce the reflected wave power value pr by changing the frequency of the output forward wave power PF (forward wave voltage VF). Hereafter, this function will be referred to as "frequency matching". When frequency matching is performed, the fundamental frequency of the forward wave voltage VF is not constant but fluctuates, but the term "fundamental frequency" will be used to include cases where the fundamental frequency fluctuates.

[0025] Furthermore, 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 (IMD). Even when frequency modulation control is performed, the fundamental frequency of the forward wave voltage VF is not constant but fluctuates, but the term "fundamental frequency" is used.

[0026] The high-frequency power supply 10 is feedback controlled to reduce the error between the forward-wave power value pf and the target power value pt. This type of power control is called constant forward-wave power control (constant PF control). It is also possible to perform feedback control to reduce the error between the load-side power value pL and the target power value pt. This type of power control is called constant load-side power control (constant PL control). However, in the following explanation, we will mainly use the case of constant forward-wave power control as an example.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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 side (for example, the input terminal) towards the load 50 side to 50Ω.

[0032] 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.

[0033] <Details of the high-frequency power supply 10> The configuration of the high-frequency power supply 10 will be described below with reference to Figure 1. The high-frequency power supply 10 includes a power value setting unit 11, a power value control unit 12, a high-frequency power output unit 13, a common sensor 14, an information calculation unit 15, and a power supply communication unit 16. The power value control unit 12 includes a comparison unit 121 and a compensation unit 122. Although an output terminal is usually provided at the output terminal 101 of the high-frequency power supply 10, it is not shown in the illustration.

[0034] The high-frequency power output unit 13 amplifies the high-frequency signal output from an oscillator (not shown) and outputs high-frequency power (traveling wave power) having an output frequency in the RF band. At that time, the output level of the high-frequency power output unit 13 is controlled based on the control signal Pcnt from the power value control unit 12, so that it can output high-frequency power with a desired power value.

[0035] The common sensor 14 is located on the load side of the high-frequency power output unit 13 and detects information for calculating the load-side impedance Z as seen from the position of the common sensor 14 towards the load 50, or information for calculating the reflection coefficient ρ at the position of the common sensor 14. Since the load-side impedance Z and the reflection coefficient ρ are mutually convertible, either can be detected.

[0036] When calculating the load-side impedance Z, for example, a voltage detector and a current detector are used as the common sensor 14. In this case, the voltage at the location of the common sensor 14 is detected by the voltage detector, and a voltage detection signal v is output as the detection signal. Also, the current at the location of the common sensor 14 is detected by the current detector, and a current detection signal i is output as the detection signal. The voltage detection signal v and the current detection signal i are output to the information calculation unit 15.

[0037] When calculating the reflection coefficient ρ at the position of the common sensor 14, for example, a directional coupler is used as the common sensor 14. In this case, the forward wave voltage VF output from the high-frequency power output unit 13 is detected, and a forward wave voltage detection signal vf 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 vr is output as the detection signal. The forward wave voltage detection signal vf and the reflected wave voltage detection signal vr are output to the information calculation unit 15.

[0038] An A / D converter (not shown) may be provided between the common sensor 14 and the information calculation unit 15. Furthermore, a filter for removing unwanted signal components (e.g., harmonic components) may be provided between the common sensor 14 and the information calculation unit 15. In this case, the filter type can be selected as appropriate.

[0039] The information calculation unit 15 includes a load information calculation unit 151 and a power information calculation unit 152.

[0040] The load information calculation unit 151 can calculate the reflection coefficient ρ or the load-side impedance Z based on the detection signal output from the common sensor 14. When this information is used as load information IFL, the information calculation unit 15 can output the load information IFL to the impedance matching control unit 39 of the impedance matching unit 30. The transmission from the information calculation unit 15 to the impedance matching control unit 39 is performed via the power supply communication unit 16, the communication cable 73, and the impedance matching unit communication unit 44 of the impedance matching unit 30. 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.

[0041] The power information calculation unit 152 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 common sensor 14. This information related to high-frequency power is necessary for controlling the high-frequency power supply 10 and is therefore output to the power value control unit 12. It is not necessary to calculate all of the information related to high-frequency power. For example, if the load-side power value pL is not used for control, it does not need to be calculated.

[0042] Furthermore, the above-mentioned information related to high-frequency power can be output to the impedance matching control unit 39 of the impedance matching unit 30. The impedance matching unit 30 can utilize the above-mentioned information related to high-frequency power for control. For example, the impedance matching unit 30 may be configured to start matching operation when the traveling wave power value pf exceeds a predetermined threshold.

[0043] 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.

[0044] (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.

[0045] (2) Load side impedance Z The load impedance Z can be calculated, for example, from the voltage detection signal v and the current detection signal i. Alternatively, the load impedance Z can be calculated based on, for example, the magnitude of the voltage detection signal v, the magnitude of the current detection signal i, and the phase difference θ between the voltage detection signal v and the current detection signal i. Note that the reflection coefficient ρ and the load impedance Z are mutually convertible. Therefore, in the following, only the reflection coefficient ρ or the load impedance Z may be explained.

[0046] (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 vf^2 / R (where R is the gain equivalent to the resistance value).

[0047] (4) Reflected wave power value pr The reflected wave power value pr can be calculated, for example, using the reflected wave voltage detection signal vr^2 / R (where R is the gain equivalent to the resistance value).

[0048] (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.

[0049] (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).

[0050] In this embodiment, since constant forward wave power control is performed in the high-frequency power supply 10, the information calculation unit 15 outputs the calculated forward wave power value pf to the power value control unit 12. However, when performing constant load-side power control, it is sufficient to output the calculated load-side power value pL to the power value control unit 12. In addition, the absolute value of the reflection coefficient Γ may be used, but its explanation is omitted.

[0051] The power value setting unit 11 sets a target power value pt for the traveling wave power PF output from the high-frequency power supply 10 (high-frequency power output unit 13) and outputs it to the power value control unit 12.

[0052] As described above, the power value control unit 12 has a comparison unit 121 and a compensation unit 122.

[0053] The comparison unit 121 subtracts the traveling wave power value pf from the target power value pt and outputs the subtraction result as error information Δpf to the compensation unit 122.

[0054] The compensation unit 122 generates a control signal Pcnt to control the power value of the traveling wave power PF (traveling wave power value pf) according to the error information Δpf, and outputs it to the high-frequency voltage output unit 13.

[0055] In one example, the control signal Pcnt is a control signal for controlling the amplitude of the traveling wave voltage VF. In this case, the amplitude of the traveling wave voltage VF is adjusted by the control signal Pcnt, and consequently, the traveling wave power value pf can be adjusted. For example, if the target power value pt is 1,000 [W] and the traveling wave power value pf is 950 [W], then there is a 50 [W] deficit compared to the target power value pt. Therefore, the compensation unit 122 sets the magnitude of the amplitude control signal Pcnt to increase the traveling wave power value pf supplied to the load 50 by 50 [W] and outputs it. For such control of the traveling wave power PF, known methods such as PI control and PID control can be used.

[0056] The power supply communication unit 16 communicates with the impedance matching unit 44 via the communication cable 73. In this embodiment, the information calculated by the information calculation unit 15 is transmitted to the impedance matching unit 44. The transmitted information is then transmitted from the impedance matching unit 44 to the impedance matching control unit 39. Communication with the impedance matching unit 30 can be performed using, for example, RS485 communication or optical fiber communication, but the communication method is not limited.

[0057] In this embodiment, communication with the impedance matching unit 30 is described, but the system is not limited to this. For example, it can communicate with a higher-level control device. When communicating with a higher-level control device, for example, the system can receive a target power value pt from the higher-level control device. It can also transmit information calculated by the information calculation unit 15 to the higher-level control device.

[0058] <Details of Impedance Matching Device 30> The impedance matching unit 30 includes 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 151, a matching control unit 39, a storage unit 43, and a matching unit communication unit 44. While the input terminal 301 and output terminal 302 of the impedance matching unit 30 are typically provided with input and output terminals, these are not shown in the illustration.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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 input terminal of the impedance matcher 30 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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 adding 1 rotation to the rotation angle of the rotation axis when the minimum capacitance of the variable capacitor (100pF) is set as 0 degrees for control purposes.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] Furthermore, the variable capacitor is not limited to those that change capacitance by changing the relative positions of the electrodes. For example, it may also be a variable capacitor of the type that changes the overall capacitance by connecting multiple capacitors in parallel with a switch and changing the state of the switch (ON / OFF).

[0074] 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.

[0075] 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.

[0076] The motor is, for example, a stepping motor. Of course, other types of motors (such as servo motors) can also be used, but in this embodiment, we will describe the case in which a stepping motor is used. Here, a stepping motor is a motor that rotates by moving in fixed increments of angle, and the corresponding driver receives the pulse signal output from the control unit as a command signal and operates the stepping motor based on that command signal. When using a stepping motor in this way, it is easy to understand that the position of the movable electrode is represented by the number of steps corresponding to the number of pulse signals given to the stepping motor. For example, if the rotation angle of the rotation axis rotates from 0 to 3,600 degrees (10 rotations), and it is necessary to change the stepping motor by 1,000 steps, the position of the movable electrode can be represented by 0 to 1,000 steps.

[0077] The first position detection unit 35 detects the rotation angle of the first drive unit 33 and includes, 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 includes, for example, an encoder. The detected rotation angle is output to the matching control unit 39 as rotation angle information Dc2.

[0078] Such a first position detection unit 35 and a second position detection unit 36 ​​are examples of the position acquisition means of the present invention.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] The matching control unit 39 performs matching operations using load information IFL transmitted from the matching unit communication unit 44, rotation angle information Dc1 output from the first position detection unit 35, and rotation angle information Dc2 output from the second position detection unit 36.

[0085] 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).

[0086] 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.

[0087] As described above, the matching unit communication unit 44 communicates with the power supply communication unit 16 via the communication cable 73. This communication uses, for example, RS485 communication or optical fiber communication, enabling high-speed and stable information transmission.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] In this embodiment, a common sensor 14 is provided on the load side of the high-frequency power output unit 13 for both the high-frequency power supply 10 and the impedance matching unit 30. Based on the information detected by this common sensor 14, the high-frequency power supply 10 and the impedance matching unit 30 perform their respective controls.

[0093] Therefore, the problem of discrepancies in information (e.g., power value, reflection coefficient) calculated based on information detected by dedicated sensors installed in both the high-frequency power supply 10 and the impedance matching unit 30, as in the conventional method, does not occur. In addition, since only one sensor is needed instead of the separate sensors required for the high-frequency power supply and impedance matching unit, the installation space for the sensor can be reduced, and costs can be lowered.

[0094] Figure 2 shows another example configuration of a high-frequency power supply system. In the configuration shown in Figure 1, the load information calculation unit 151 and the power information calculation unit 152 were located within the high-frequency power supply 10. In contrast, the configuration shown in Figure 2 differs in that the load information calculation unit 151 is located within the impedance matching unit 30, and the power information calculation unit 152 is located within the high-frequency power supply 10. Consequently, in the configuration shown in Figure 2, the detection signal detected by the common sensor 14 is input to the power information calculation unit 152 located within the high-frequency power supply 10, and also to the load information calculation unit 151 located within the impedance matching unit 30 via cable 74. Furthermore, the load information IFL calculated by the load information calculation unit 151 is input to the matching control unit 39, which differs from the configuration shown in Figure 1. Even with this configuration, the same effects as the configuration in Figure 1 can be obtained.

[0095] Furthermore, it is preferable that the cable 74 between the high-frequency power supply 10 and the impedance matching unit 30 be a coaxial multi-cable. Since a coaxial multi-cable is made up of multiple coaxial cables combined into a single cable, even when transmitting multiple types of signals (for example, two types such as a forward wave voltage detection signal vf and a reflected wave voltage detection signal vr, and two types such as a voltage detection signal v and a current detection signal i), information can be transmitted without being affected by differences in cable length (for example, phase shift).

[0096] 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.

[0097] 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.

[0098] 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 common sensor 14, 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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 34a, the first position detection unit 35a, and the second position detection unit 36a shown in Figure 1, respectively. Therefore, their explanation is omitted.

[0103] Furthermore, similar to variable capacitors, the position of the movable winding, the rotation angle of the variable inductor's rotation 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, from 0 to 1,000 steps.

[0104] Although the rotation angle of the rotating shaft differs between variable inductors and variable capacitors, the concepts of minimum structural inductance and minimum controllable inductance are the same as those for minimum capacitance and minimum controllable capacitance of a variable capacitor.

[0105] 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.

[0106] Next, the effects of this embodiment will be described. According to the high-frequency power supply system of this embodiment, since a common sensor (common sensor 14) is used in both the high-frequency power supply 10 and the impedance matching unit 30, the problem of differences in information (e.g., power value, reflection coefficient) calculated based on information detected by dedicated sensors provided in each of the high-frequency power supply 10 and the impedance matching unit 30, as in the conventional system, does not occur.

[0107] Furthermore, since only one sensor is needed instead of the high-frequency power supply 10 and impedance matching unit that were previously required for each, the installation space for the sensor can be reduced, and costs can be lowered.

[0108] Furthermore, the high-frequency power supply 10 and the impedance matching unit 30 are usually housed in separate enclosures. Therefore, when using a common sensor 14, it is necessary to place the common sensor 14 in one of the enclosures. In that case, it becomes necessary to transmit the detection signal acquired by the common sensor 14, or the information calculated using that detection signal, to the other enclosure by some means (communication, cable connection, etc.).

[0109] However, in either the case of communication or cable connection, the possibility of a disconnection cannot be ruled out. If a disconnection occurs when the common sensor 14 is placed inside the impedance matching unit, the power value control in the high-frequency power supply may not be performed properly, and the output power value may become maximum. On the other hand, even if a disconnection occurs when the common sensor 14 is placed inside the high-frequency power supply, the matching accuracy will only decrease slightly. For this reason, it is preferable to place the common sensor 14 inside the high-frequency power supply 10. For this reason, in this embodiment, as shown in Figure 1, the common sensor 14 is placed inside the high-frequency power supply 10.

[0110] 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]

[0111] 1. High-frequency power supply system 10 High frequency power supply 11 Power Value Setting Unit 12 Power Value Control Unit 121 Comparison Section 122 Compensation Department 13. High-frequency power output section 14 Common Sensors 15. Information Calculation Unit 16 Power communication section 30 Impedance Matching Devices 32 Matching circuit 33 First drive unit 34 Second drive unit 35 First position detection unit 36 Second position detection unit 39 Control unit for matching unit 43 Storage section 44 Communication unit for matching unit 50 Load (Plasma Processing Equipment) 151 Load Information Calculation Unit 152 Power Information Calculation Unit

Claims

1. A high-frequency power supply system that supplies high-frequency power to a load, A high-frequency power output section that outputs high-frequency power by amplifying a high-frequency signal, A sensor provided on the load side of the aforementioned high-frequency power output unit, A power control unit that acquires information related to high-frequency power calculated based on the information detected by the aforementioned sensor, and controls the power value of the high-frequency power output from the high-frequency power supply using the acquired information, 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 matching control unit that acquires the reflection coefficient or load-side impedance calculated based on the information detected by the sensor, and uses the acquired reflection coefficient or load-side impedance to provide a command signal to the driving means to change the positional relationship of the electrode or winding so that the reflected wave power is reduced, A high-frequency power supply system equipped with this feature.

2. The aforementioned over-power supply system is A high-frequency power supply that outputs high-frequency power, obtained by amplifying a high-frequency signal, toward the load, An impedance matching device is provided between the high-frequency power supply and the load, It is equipped with, The high-frequency power output unit, the sensor, and the power control unit are arranged within the high-frequency power supply. The matching circuit, the driving means, and the matching control unit are arranged within the impedance matching unit. The high-frequency power supply system according to claim 1.

3. A power information calculation unit calculates information related to the high-frequency power output from the high-frequency power output unit based on the information detected by the sensor, A load information calculation unit calculates and outputs the reflection coefficient or load-side impedance based on the information detected by the aforementioned sensor, It also has the following features: The power information calculation unit and the load information calculation unit are located within the high-frequency power supply. The power control unit acquires information related to high-frequency power from the power information calculation unit, The matching control unit obtains the reflection coefficient or load-side impedance from the load information calculation unit. The high-frequency power supply system according to claim 2.

4. A power information calculation unit calculates information related to the high-frequency power output from the high-frequency power output unit based on the information detected by the sensor, A load information calculation unit calculates and outputs the reflection coefficient or load-side impedance based on the information detected by the aforementioned sensor, It also has the following features: The power information calculation unit is located within the high-frequency power supply. The load information calculation unit is located within the impedance matching unit. The power control unit acquires information related to high-frequency power from the power information calculation unit, The matching control unit obtains the reflection coefficient or load-side impedance from the load information calculation unit. The high-frequency power supply system according to claim 2.

5. The transmission of information between the high-frequency power supply and the impedance matching device is performed using communication means. The high-frequency power supply system according to claim 3 or claim 4.

6. The transmission of information between the high-frequency power supply and the impedance matching device is performed using a coaxial multi-cable. The high-frequency power supply system according to claim 3 or claim 4.

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