46 is grounded. Further, when the radio-frequency power supply 36 is connected to the upper electrode 46, not to the lower electrode, via the matching device 40, the upper electrode 46 is not grounded, and the upper electrode 46 and the chamber body 12 are electrically separated from each other.

The upper electrode 46 includes a top plate 48 and a support 50. A plurality of gas discharge holes 48a is formed in the top plate 48. The top plate 48 is formed of a silicon-based material such as, for example, Si or SiC. The support 50 is a member that detachably supports the top plate 48, is formed of a conductor such as aluminum, and has a plasma-resistant film formed on its surface.

A gas buffer chamber 50b is formed inside the support 50. Further, a plurality of gas holes 50a is formed in the support 50. Each of the plurality of gas holes 50a extends from the gas buffer chamber 50b and communicates with the plurality of gas discharge holes 48a. A gas supply pipe 54 is connected to the gas buffer chamber 50b. A gas source 56 is connected to the gas supply pipe 54 via a flow rate controller 58 (e.g., a mass flow controller) and an on-off valve 60. The gas from the gas source 56 is supplied to the internal space of the chamber 10 through the flow rate controller 58, the on-off valve 60, the gas supply pipe 54, the gas buffer chamber 50b, and the plurality of gas discharge holes 48a. The flow rate of the gas supplied from the gas source 56 to the internal space of the chamber 10 is adjusted by the flow rate controller 58.

An exhaust port 12e is provided at the bottom of the chamber body 12 below the space between the susceptor 16 and the side wall of the chamber body 12. An exhaust pipe 64 is connected to the exhaust port 12e. The exhaust pipe 64 is connected to an exhaust device 66. The exhaust device 66 includes a pressure regulator such as an automatic pressure control valve and a vacuum pump such as a turbo molecular pump. The exhaust device 66 depressurizes the internal space of the chamber 10 to a designated pressure.

The plasma processing apparatus 1 further includes a main control unit 70. The main control unit 70 includes one or more microcomputers. The main control unit 70 may include a storage device such as a processor and a memory, an input device such as a keyboard, a display device, and a signal input/output interface. The processor of the main control unit 70 executes software (program) stored in the storage device to control the individual operation of each part of the plasma processing apparatus 1 and the entire operation (sequence) of the plasma processing apparatus 1 according to the recipe data. The main control unit 70 controls, for example, a radio-frequency power supply 36, a radio-frequency power supply 38, a matching device 40, a matching device 42, a flow rate controller 58, an on-off valve 60, and an exhaust device 66.

When plasma processing is performed in the plasma processing apparatus 1, the gate valve 12g is first opened. Next, the substrate W is loaded into the chamber 10 via the opening 12p and placed on the electrostatic chuck 18. Then, the gate valve 12g is closed. Next, the processing gas is supplied from the gas source 56 to the internal space of the chamber 10, and the exhaust device 66 is operated to set the pressure in the internal space of the chamber 10 to the designated pressure. Further, radio-frequency power RF1 and/or radio-frequency power RF2 is supplied to the susceptor 16. Further, a DC voltage from the DC power supply 24 is applied to the electrode 20 of the electrostatic chuck 18, and the substrate W is held by the electrostatic chuck 18. Then, the processing gas is excited by a radio-frequency electric field formed between the susceptor 16 and the upper electrode 46. As a result, plasma is generated in the processing region PS.

In the following descriptions, FIGS. 2 to 3 will be referenced together with FIG. 1. FIG. 2 is a diagram illustrating an example of a timing chart of the first radio-frequency power and the second radio-frequency power. FIG. 3 is a diagram illustrating another example of a timing chart of the first radio-frequency power and the second radio-frequency power. The plasma processing apparatus 1 is configured to utilize at least one of a modulated wave MW1 of the radio-frequency power RF1 and a modulated wave MW2 of the radio-frequency power RF2 for plasma processing in the chamber 10 during a period P1. The modulated wave MW1 is generated by the radio-frequency power supply 36. The modulated wave MW2 is generated by the radio-frequency power supply 38. As illustrated by the dotted line in FIGS. 2 and 3, either a continuous wave CW1 of the radio-frequency power RF1 or a continuous wave CW2 of the radio-frequency power RF2 may be used in the period P1. The continuous wave CW1 is generated by the radio-frequency power supply 36. The continuous wave CW2 is generated by the radio-frequency power supply 38. The mode in which the modulated wave MW1 and the modulated wave MW2 are used in the period P1 is a first mode. The mode in which the modulated wave MW1 and the modulated wave CW2 are used in the period P1 is a second mode. The mode in which the modulated wave CW1 and the modulated wave MW2 are used in the period P1 is a third mode.

The period P1 includes alternating first sub-period SP11 and second sub-period SP12. The modulated wave MW1 is generated by the radio-frequency power supply 36 so that the power level of the radio-frequency power RF1 in the first sub-period SP11 is higher than the power level of the radio-frequency power RF1 in the second sub-period SP12. The power level of the radio-frequency power RF1 in the second sub-period SP12 may be 0 W. The modulated wave MW2 is generated by the radio-frequency power supply 38 so that the power level of the radio-frequency power RF2 in the first sub-period SP11 is higher than the power level of the radio-frequency power RF2 in the second sub-period SP12. The power level of the radio-frequency power RF2 in the second sub-period SP12 may be 0 W.

The first sub-period SP11 and the subsequent second sub-period SP12 constitute one cycle CP. The ratio of the first sub-period SP11 in one cycle CP, that is, the duty ratio may be any value. For example, the duty ratio may be controlled to a value within the range of 10% or more and 90% or less. Further, the reciprocal of the one-cycle CP, that is, the modulation frequency may be controlled to any frequency. However, the modulation frequency is lower than the fundamental frequency f_B1and the fundamental frequency f_B2. The modulation frequency may be, for example, a frequency in the range of 0.1 kHz or more and 100 kHz or less.

Further, the plasma processing apparatus 1 is configured to utilize the continuous wave CW1 and the continuous wave CW2 in a period P2. That is, the radio-frequency power RF1 and the radio-frequency power RF2 are continuously supplied between the start time of the period P2 and the end time of the period P2. The time length of the period P2 is longer than the time length of the one-cycle CP.

The period P1 and the period P2 are two consecutive periods. As illustrated in FIG. 2, the period P1 of the two consecutive periods may be the preceding period PA and the period P2 may be the subsequent period PB. Further, as illustrated in FIG. 3, the period P2 of the two consecutive periods may be the preceding period PA and the period P1 may be the subsequent period PB. The period P1 and the period P2 may be repeated alternately. That is, the radio-frequency power supply 36 supplies a power wave W11 in the preceding period PA. The power wave W11 is one of the modulated wave MW1 and the continuous wave CW1. The radio-frequency power supply 36 supplies the power wave W11 or the power wave W12 in the subsequent period PB. The power wave W12 is the other of the modulated wave MW1 and the continuous wave CW1. The radio-frequency power supply 38 supplies a power wave W21 in the preceding period PA. The power wave W21 is one of the modulated wave MW2 and the continuous wave CW2. The radio-frequency power supply 38 supplies the power wave W21 or a power wave W22 in the subsequent period PB. The power wave W22 is the other of the modulated wave MW2 and the continuous wave CW2. In the subsequent period PB, at least one of the power wave W12 and the power wave W22 is supplied.

Hereinafter, the radio-frequency power supply 36, the matching device 40, the radio-frequency power supply 38, and the matching device 42 will be described in detail with reference to FIGS. 4 to 7. FIG. 4 is a diagram illustrating a configuration example of the first radio-frequency power supply and the first matching device of the plasma processing apparatus illustrated in FIG. 1. FIG. 5 is a diagram illustrating a configuration example of a sensor of the first matching device of the plasma processing apparatus illustrated in FIG. 1. FIG. 6 is a diagram illustrating a configuration example of the second radio-frequency power supply and the second matching device of the plasma processing apparatus illustrated in FIG. 1. FIG. 7 is a diagram illustrating a configuration example of a sensor of the second matching device of the plasma processing apparatus illustrated in FIG. 1.

As illustrated in FIG. 4, in the embodiment, the radio-frequency power supply 36 includes an oscillator 36a, a power amplifier 36b, a power sensor 36c, and a power supply control unit 36e. The power supply control unit 36e includes a processor such as a CPU. The power supply control unit 36e gives a control signal to each of the oscillator 36a, the power amplifier 36b, and the power sensor 36c to control the oscillator 36a, the power amplifier 36b, and the power sensor 36c. The power supply control unit 36e uses the signal given from the main control unit 70 and the signal given from the power sensor 36c to generate a control signal given to each of the oscillator 36a, the power amplifier 36b, and the power sensor 36c.

The signal given from the main control unit 70 to the power supply control unit 36e includes a first frequency setting signal and a mode setting signal. The first frequency setting signal is a signal that designates the set frequency of the radio-frequency power RF1. The mode setting signal is a signal that designates the selected mode from the first to third modes. When the first mode or the second mode is designated, the signal given from the main control unit 70 to the power supply control unit 36e further includes a first modulation setting signal. The first modulation setting signal is a signal that designates the modulation frequency and duty ratio of the modulated wave MW1. The first modulation setting signal is also a signal that designates the power level of the modulated wave MW1 in the first sub-period SP11 and the power level of the modulated wave MW1 in the second sub-period SP12. When the third mode is designated, the signal given from the main control unit 70 to the power supply control unit 36e further includes a first power level setting signal that designates the power of the continuous wave CW1.

The power supply control unit 36e controls the oscillator 36a to output a radio-frequency signal having a set frequency (e.g., the fundamental frequency f_B1) designated by the first frequency setting signal. The output of the oscillator 36a is connected to the input of the power amplifier 36b. The power amplifier 36b generates radio-frequency power RF1 by amplifying the radio-frequency signal output from the oscillator 36a. The power amplifier 36b is controlled by the power supply control unit 36e.

When the first mode or the second mode is designated, the power supply control unit 36e controls the power amplifier 36b to generate the modulated wave MW1 from the radio-frequency signal in response to the first modulation setting signal during the period P1. When the first mode or the second mode is designated, the power supply control unit 36e controls the power amplifier 36b to generate the continuous wave CW1 from the radio-frequency signal in response to the first power level setting signal during the period P2. When the third mode is designated, the power supply control unit 36e controls the power amplifier 36b to generate the continuous wave CW1 from the radio-frequency signal in response to the first power level setting signal during the period P1 and the period P2.

The power sensor 36c is provided at the rear end of the power amplifier 36b. The power sensor 36c includes a directional coupler, a traveling wave detector, and a reflected wave detector. The directional coupler gives a part of the traveling wave of the radio-frequency power RF1 to the traveling wave detector and the reflected wave to the reflected wave detector. A first frequency specifying signal for specifying the set frequency of the radio-frequency power RF1 is given to the power sensor 36c from the power supply control unit 36e. The traveling wave detector generates a measured value of the power level of a component having the same frequency as the set frequency specified from the first frequency specifying signal among all the frequency components of the traveling wave, that is, a measured value P_f11of the power level of the traveling wave. The measured value P_f11is given to the power supply control unit 36e.

The first frequency specifying signal is also given to the reflected wave detector from the power supply control unit 36e. The reflected wave detector generates a measured value of the power level of a component having the same frequency as the set frequency specified from the first frequency specifying signal among all the frequency components of the reflected wave, that is, a measured value P_r11of the power level of the reflected wave. The measured value P_f11is given to the power supply control unit 36e. Further, the reflected wave detector generates a measured value of the total power level of all frequency components of the reflected wave, that is, a measured value P_r12of the power level of the reflected wave. The measured value P_r12is given to the power supply control unit 36e for the protection of the power amplifier 36b.

In the embodiment, the radio-frequency power supply 36 may perform a load power control during the period P1. That is, the radio-frequency power supply 36 may adjust the power level of the radio-frequency power RF1 so that the load power level of the radio-frequency power RF1 in the period P1 approaches or matches the specified target power level. The power supply control unit 36e may control the power amplifier 36b in the load power control of the radio-frequency power supply 36.

In the load power control when the first mode or the second mode is designated, the power supply control unit 36e may control the power amplifier 36b to adjust the power level of the modulated wave MW1 in the first sub-period SP11. The power level of the modulated wave MW1 in the first sub-period SP11 is adjusted so that the load power level PL11 in the monitoring period MP1 approaches or matches the specified target power level.

The monitoring period MP1 is a period within the first sub-period SP11. The monitoring period MP1 may be a period that starts after a predetermined time length has elapsed from the start time of the first sub-period SP11. The monitoring period MP1 is designated by the main control unit 70. The load power level P_L11is a difference between the power level of the traveling wave of the radio-frequency power RF1 in the monitoring period MP1 and the power level of the reflected wave of the radio-frequency power RF1 in the monitoring period MP1. The load power level P_L11is obtained as a difference between the measured value P_f11and the measured value P_r11during the monitoring period MP1. The load power level P_L11may be obtained as a difference between the average value of the measured value P_f11and the average value of the measured value P_r11during the monitoring period MP1. Alternatively, the load power level P_L11may be obtained as a difference between the moving average value of the measured value P_f11and the moving average value of the measured value P_r11in the plurality of monitoring periods MP1.

When the power level of the modulated wave MW1 in the second sub-period SP12 is not 0 W, the radio-frequency power supply 36 may execute the load power control of the modulated wave MW1 in the second sub-period SP12. In the load power control, the power supply control unit 36e may control the power amplifier 36b to adjust the power level of the modulated wave MW1 in the second sub-period SP12. The power level of the modulated wave MW1 in the second sub-period SP12 is adjusted so that the load power level P_L12in the monitoring period MP2 approaches or matches the specified target power level.

The monitoring period MP2 may be a period that coincides with the second sub-period SP12. Alternatively, the monitoring period MP2 may be a period within the second sub-period SP12, and may be a period that starts after a predetermined time length has elapsed from the start time of the second sub-period SP12. The monitoring period MP2 is designated by the main control unit 70. The load power level P_L12is a difference between the power level of the traveling wave of the radio-frequency power RF1 in the monitoring period MP2 and the power level of the reflected wave of the radio-frequency power RF1 in the monitoring period MP2. The load power level P_L12is obtained as the difference between the measured value P_f11and the measured value P_r11during the monitoring period MP2. The load power level P_L12may be obtained as the difference between the average value of the measured value P_f11and the average value of the measured value P_r11during the monitoring period MP2. Alternatively, the load power level P_L12may be obtained as the difference between the moving average value of the measured value P_f11and the moving average value of the measured value P_r11in the plurality of monitoring periods MP2.

The radio-frequency power supply 36 may also perform load power control even when the third mode is designated. In the load power control when the third mode is designated, the power supply control unit 36e may control the power amplifier 36b to adjust the power level of the continuous wave CW1 in the period P1. The power level of the continuous wave CW1 in the period P1 is adjusted so that the average value of the load power level P_L11in the monitoring period MP1 and the load power level P_L12in the monitoring period MP2 matches or approaches the specified target power level.

The matching device 40 is configured to set the load-side impedance of the radio-frequency power supply 36, that is, the load impedance. In each of the first and second modes, the matching device 40 may set the load impedance of the radio-frequency power supply 36 in the period P1 to a target impedance different from the output impedance of the radio-frequency power supply 36. The load impedance of the radio-frequency power supply 36 in the period P1 may be specified by the measured value of the load impedance of the radio-frequency power supply 36 in the monitoring period MP1.

In the third mode, the matching device 40 may match the load impedance of the radio-frequency power supply 36 in the period P1 with the output impedance of the radio-frequency power supply 36. Alternatively, the matching device 40 sets the load impedance of the radio-frequency power supply 36 in the period P1 to a target impedance different from the output impedance of the radio-frequency power supply 36 in the third mode as well as in the first and second modes.

The matching device 40 matching devices the load impedance of the radio-frequency power supply 36 in the period P2 to the target impedance for the subsequent period PB in each of the first mode and the second mode. That is, the matching device 40 is configured to gradually change the load impedance of the radio-frequency power supply 36 to the target impedance for the subsequent period PB in the period P2 before or after the power generated by the radio-frequency power supply 36 is switched from the power wave W11 to the power wave W12.

As illustrated in FIGS. 8 and 9, in each of the first and second modes, the matching device 40 gradually changes the load impedance of the radio-frequency power supply 36 so that the absolute value |Γ₁| of the reflectance coefficient Γ₁is gradually changed to the set target value for the subsequent period PB in the period P2. As illustrated in FIG. 8, when the subsequent period PB is the period P2 in each of the first and second modes, the set target value of the absolute value |Γ₁| of the reflectance coefficient Γ₁for the subsequent period PB may be zero. As illustrated in FIG. 9, when the subsequent period PB is the period P1 in each of the first and second modes, the set target value of the absolute value |Γ₁| of the reflectance coefficient Γ₁for the subsequent period PB is larger than zero, for example, 0.3 or more and 0.5 or less.

The period P2 includes a plurality of consecutive sub-period SPs. The plurality of sub-period SPs include sub-periods SP₁, SP₂, . . . , SP_N. The matching device 40 may gradually change the load impedance of the radio-frequency power supply 36 so that the absolute value |Γ₁| of the reflectance coefficient Γ₁in the period P2 is gradually changed through the sub-periods SP₁, SP₂, . . . , SP_Nto the set target value for the subsequent period PB. As illustrated in FIG. 8, when the subsequent period PB is the period P2, the matching device 40 gradually changes the load impedance of the radio-frequency power supply 36 through the sub-periods SP₁, SP₂, . . . , SP_Nin the period P2 after the start of the subsequent period PB (period P2). As illustrated in FIG. 9, when the subsequent period PB is the period P1, the matching device 40 gradually changes the load impedance of the radio-frequency power supply 36 through the sub-periods SP₁, SP₂, . . . , SP_Nin the period P2 before the start of the subsequent period PB (period P1). The period P2 further includes a sub-period SP_(N+1). The sub-period SP_(N+1)is a period continuous with the sub-period SP_N. The matching device 40 sets the load impedance of the radio-frequency power supply 36 so that the absolute value |Γ₁| of the reflectance coefficient Γ₁in the sub-period SP_(N+1)is set as the set target value for the subsequent period PB. Hereinafter, each of the sub-periods SP₁, SP₂, . . . , SP_N, SP_(N+1)may be referred to as a sub-period SP_i. The symbol “i” refers to an index that is an integer of 1 or more and N+1 or less.

In the third mode, the matching device 40 may match the load impedance of the radio-frequency power supply 36 in the period P2 with the output impedance of the radio-frequency power supply 36. The matching device 40 may gradually change the load impedance of the radio-frequency power supply 36 in the period P2 to the target impedance for the subsequent period PB in the third mode as well as in the first and second modes.

In the embodiment, as illustrated in FIG. 4, the matching device 40 includes a matching circuit 40a, a sensor 40b, a controller 40c, an actuator 40d, and an actuator 40e. The matching circuit 40a may include a variable reactance element 40g and a variable reactance element 40h. Each of the variable reactance element 40g and the variable reactance element 40h is, for example, a variable capacitor. The matching circuit 40a may further include an inductor and the like.

The controller 40c operates under the control of the main control unit 70. The controller 40c adjusts the load impedance of the radio-frequency power supply 36 according to the measured value of the load-side impedance (i.e., the load impedance) of the radio-frequency power supply 36 given by the sensor 40b. The controller 40c adjusts the load impedance of the radio-frequency power supply 36 by controlling the actuator 40d and the actuator 40e and adjusting the reactance of each of the variable reactance element 40g and the variable reactance element 40h. The actuator 40d and the actuator 40e are, for example, motors.

The sensor 40b is configured to acquire a measured value of the load impedance of the radio-frequency power supply 36. In the embodiment, the measured value of the load impedance of the radio-frequency power supply 36 is acquired as a moving average value. As illustrated in FIG. 5, the sensor 40b may include a current detector 102A, a voltage detector 104A, filters 106A and 108A, average value calculators 110A and 112A, moving average value calculators 114A and 116A, and an impedance calculator 118A.

The voltage detector 104A detects the voltage waveform of the radio-frequency power RF1 transmitted on the power feeding line 43, and outputs a voltage waveform analog signal representing the voltage waveform. This voltage waveform analog signal is input to the filter 106A. The filter 106A generates a voltage waveform digital signal by digitizing the input voltage waveform analog signal. The filter 106A receives the above-mentioned first frequency specifying signal from the power supply control unit 36e and extracts only the frequency component corresponding to the frequency specified by the first frequency specifying signal from the voltage waveform digital signal, thereby generating a filtration voltage waveform signal. The filter 106A may be composed of an FPGA (Field Programmable Gate Array).

The filtration voltage waveform signal generated by the filter 106A is output to the average value calculator 110A. The average value calculator 110A receives a monitoring period setting signal from the main control unit 70. The average value calculator 110A obtains the average value of the voltage within the period specified from the monitoring period setting signal from the filtration voltage waveform signal. The average value calculator 110A obtains the average value V_A11of the voltage in each monitoring period MP1 as the average value of the voltage. When the third mode is designated, the average value calculator 110A may further obtain the average value V_A12of the voltage in each monitoring period MP2 as the average value of the voltage. Further, the average value calculator 110A may be composed of, for example, an FPGA.

The moving average value calculator 114A obtains the moving average value V_MA11of the average value VAI which is obtained from the voltage of the radio-frequency power RF1 in the latest and predetermined number of monitoring periods MP1 among the plurality of average values V_A11already obtained. The moving average value V_MA11is output to the impedance calculator 118A.

In the third mode, the moving average value calculator 114A may further obtain the moving average value V_MA12of the average value V_A12which is obtained from the voltage of the radio-frequency power RF1 in the latest and predetermined number of monitoring periods MP2 among the plurality of average values V_A12already obtained. The moving average value V_MA12is output to the impedance calculator 118A.

The current detector 102A detects the current waveform of the radio-frequency power RF1 transmitted on the power feeding line 43, and outputs a current waveform analog signal representing the current waveform. This voltage waveform analog signal is input to the filter 108A. The filter 108A generates a voltage waveform digital signal by digitizing the input voltage waveform analog signal. The filter 108A receives the above-mentioned first frequency specifying signal from the power supply control unit 36e and extracts only the frequency component corresponding to the frequency specified by the first frequency specifying signal from the voltage waveform digital signal, thereby generating a filtration voltage waveform signal. The filter 108A may be composed of an FPGA.

The filtration voltage waveform signal generated by the filter 108A is output to the average value calculator 112A. The average value calculator 112A receives a monitoring period setting signal from the main control unit 70. The average value calculator 112A obtains the average value of the voltage within the period specified from the monitoring period setting signal from the filtration voltage waveform signal. The average value calculator 112A obtains the average value I_A11of the current in the monitoring period MP1 in each period P1 as the average value of the current. When the third mode is designated, the average value calculator 112A may further obtain the average value I_A12of the current in each monitoring period MP2 as the average value of the current. Further, the average value calculator 112A may be composed of, for example, an FPGA.

The moving average value calculator 116A obtains the moving average value I_MA11of the average value I_A11which is obtained from the current of the radio-frequency power RF1 in the latest and predetermined number of monitoring periods MP1 among the plurality of average values I_A11already obtained. The moving average value I_MA11is output to the impedance calculator 118A.

In the third mode, the moving average value calculator 116A may further obtain the moving average value I_MA12of the average value I_A12which is obtained from the current of the radio-frequency power RF1 in the latest and predetermined number of monitoring periods MP2 among the plurality of average values I_A12already obtained. The moving average value I_MA12is output to the impedance calculator 118A.

The impedance calculator 118A obtains the moving average value Z_MA11of the load impedance of the radio-frequency power supply 36 from the moving average value I_MA11and the moving average value V_MA11. The moving average value Z_MA11is a measured value of the load impedance of the radio-frequency power supply 36 during the monitoring period MP1. In the third mode, the impedance calculator 118A may further obtain the moving average value Z_MA12of the load impedance of the radio-frequency power supply 36 from the moving average value I_MA12and the moving average value V_MA12. The moving average value Z_MA12is a measured value of the load impedance of the radio-frequency power supply 36 during the monitoring period MP2.

The controller 40c controls the matching circuit 40a in order to set the load impedance of the radio-frequency power supply 36. In the embodiment, the controller 40c sets the load impedance of the radio-frequency power supply 36 by adjusting the reactances of the variable reactance element 40g and the variable reactance element 40h through the actuator 40d and the actuator 40e.

In each of the first and second modes, the controller 40c adjusts the load impedance of the radio-frequency power supply 36 in the period P1 specified by the moving average value Z_MA11to a target impedance different from the output impedance of the radio-frequency power supply 36.

In the embodiment, the controller 40c may specify the target impedance from the set target value of the absolute value |Γ₁| of the reflectance coefficient Γ₁of the radio-frequency power RF1 in the period P1. The set target value of the absolute value |Γ₁| in the period P1 may be a value larger than 0. For example, the set target value of the absolute value |Γ₁| in the period P1 is 0.3 or more and 0.5 or less. The reflectance coefficient Γ₁is defined by the following equation (1).

Γ₁=(Z₁−Z₀₁)/(Z₁+Z₀₁) (1)

In the equation (1), Z₀₁is the characteristic impedance of the power feeding line 43, and is generally 50Ω. In the equation (1), Z₁is the target impedance. The controller 40c determines the target impedance Z₁corresponding to the set target value of the absolute value |Γ₁| in the period P1 based on the equation (1). The controller 40c sets the load impedance of the radio-frequency power supply 36 so that the load impedance of the radio-frequency power supply 36 during the period P1 specified by the moving average value Z_MA11approaches or matches the target impedance Z₁.

When the third mode is specified, the controller 40c may match the load impedance of the radio-frequency power supply 36 with the output impedance (matching point) of the radio-frequency power supply 36 during the period P1. The load impedance of the radio-frequency power supply 36 may be specified by the average value of the moving average value Z_MA11and the moving average value Z_MA12. Alternatively, the controller 40c may adjust the load impedance of the radio-frequency power supply 36 in the period P1 to a target impedance different from the output impedance of the radio-frequency power supply 36 in the third mode as well as in the first and second modes.

As described above, in each of the first and second modes, the matching device 40 may gradually change the load impedance of the radio-frequency power supply 36 so that the absolute value |Γ₁| of the reflectance coefficient Γ₁is gradually changed to the set target value for the subsequent period PB. As described above, the matching device 40 gradually changes the load impedance of the radio-frequency power supply 36 through a plurality of sub-period SPs in the period P2. The time length of each of the plurality of sub-period SPs (i.e., SP₁, SP₂, . . . , SP_N) is TL.

The target values of the absolute value |Γ₁| of the reflectance coefficient Γ₁of the radio-frequency power RF1 in the plurality of sub-periods SP₁, SP₂, . . . , SP_Nare different from each other. Of any two consecutive sub-periods included in the plurality of sub-periods SP2, the difference between the target value of the absolute value |Γ₁| of the reflectance coefficient Γ₁in one sub-period and the target value of the absolute value |Γ₁| of the reflectance coefficient Γ₁in the other period is ΔΓ₁. In addition, FIG. 8 and FIG. 9 illustrate ΔΓ₁as ΔΓ. As illustrated in FIG. 8, when the subsequent period PB is the period P2, the target value of the absolute value |Γ₁| of the reflectance coefficient Γ₁in the sub-period SP_(N+1), that is, the set target value is zero. As illustrated in FIG. 9, when the subsequent period PB is the period P1, the target value of the absolute value |Γ₁| of the reflectance coefficient Γ₁in the sub-period SP_(N+1), that is, the set target value is larger than zero, for example, 0.3 or more and 0.5 or less. In the embodiment, the TL may be set to 0.5 seconds or more and the ΔΓ₁may be set to 0.2 or less. Further, the TL may be set to 0.2 seconds or more and the ΔΓ₁may be set to 0.1 or less. In addition, the TL may be set to 0.5 seconds or more and the ΔΓ₁may be set to 0.05 or less.

The controller 40c sets the load impedance of the radio-frequency power supply 36. Specifically, the controller 40c adjusts the load impedance of the radio-frequency power supply 36 in the sub-period SP_ifrom the target value of the absolute value |Γ₁| of the reflectance coefficient Γ₁of the radio-frequency power RF1 in the sub-period SP_ito the target impedance Z₁specified based on the equation (1). Further, the controller 40c may specify the load impedance of the radio-frequency power supply 36 in the sub-period SP_ifrom the measured value of the load impedance of the radio-frequency power supply 36 obtained by the sensor 40b. The sensor 40b may obtain the measured value of the load impedance of the radio-frequency power supply 36 from the above-mentioned filtration voltage waveform signal and filtration current waveform signal.

When the third mode is specified, the controller 40c may match the load impedance of the radio-frequency power supply 36 with the output impedance (matching point) of the radio-frequency power supply 36 during the period P2. In the third mode as well as in the first and second modes, the controller 40c may gradually change the load impedance of the radio-frequency power supply 36 to the target impedance for the subsequent period PB in the period P2.

As illustrated in FIG. 6, in the embodiment, the radio-frequency power supply 38 includes an oscillator 38a, a power amplifier 38b, a power sensor 38c, and a power supply control unit 38e. The power supply control unit 38e includes a processor such as a CPU. The power supply control unit 38e gives a control signal to each of the oscillator 38a, the power amplifier 38b, and the power sensor 38c to control the oscillator 38a, the power amplifier 38b, and the power sensor 38c. The power supply control unit 38e uses the signal given from the main control unit 70 and the signal given from the power sensor 38c to generate a control signal given to each of the oscillator 38a, the power amplifier 38b, and the power sensor 38c.

The signal given from the main control unit 70 to the power supply control unit 38e includes a second frequency setting signal and the above-mentioned mode setting signal. The second frequency setting signal designates the set frequency of the radio-frequency power RF2. When the first mode or the third mode is designated, the signal given from the main control unit 70 to the power supply control unit 38e further includes a second modulation setting signal. The second modulation setting signal designates the modulation frequency and duty ratio of the modulated wave MW2. Further, the second modulation setting signal is also a signal that designates the power level of the modulated wave MW2 in the first sub-period SP11 and the power level of the modulated wave MW2 in the second sub-period SP12. In the first mode, the modulation frequency of the modulated wave MW1 and the modulation frequency of the modulated wave MW2 may be the same as each other. When the second mode is designated, the signal given from the main control unit 70 to the power supply control unit 38e further includes a second power level setting signal that designates the power of the continuous wave CW2.

The power supply control unit 38e controls the oscillator 38a to output a radio-frequency signal having a set frequency (e.g., the fundamental frequency f_B2) designated by the second frequency setting signal. The output of the oscillator 38a is connected to the input of the power amplifier 38b. The power amplifier 38b generates radio-frequency power RF2 by amplifying the radio-frequency signal output from the oscillator 38a. The power amplifier 38b is controlled by the power supply control unit 38e.

When the first mode or the third mode is designated, the power supply control unit 38e controls the power amplifier 38b to generate the modulated wave MW2 from the radio-frequency signal in response to the second modulation setting signal during the period P1. When the first mode or the third mode is designated, the power supply control unit 38e controls the power amplifier 38b to generate the continuous wave CW2 from the radio-frequency signal in response to the second power level setting signal during the period P2. When the second mode is designated, the power supply control unit 38e controls the power amplifier 38b to generate the continuous wave CW2 from the radio-frequency signal in response to the second power level setting signal during the period P1 and the period P2.

The power sensor 38c is provided at the rear end of the power amplifier 38b. The power sensor 38c includes a directional coupler, a traveling wave detector, and a reflected wave detector. The directional coupler gives a part of the traveling wave of the radio-frequency power RF2 to the traveling wave detector and the reflected wave to the reflected wave detector. A second frequency specifying signal for specifying the set frequency of the radio-frequency power RF2 is given to the power sensor 38c from the power supply control unit 38e. The traveling wave detector generates a measured value of the power level of a component having the same frequency as the set frequency specified from the second frequency specifying signal among all the frequency components of the traveling wave, that is, a measured value P_f21of the power level of the traveling wave. The measured value P_f21is given to the power supply control unit 38e.

The second frequency specifying signal is also given to the reflected wave detector from the power supply control unit 38e. The reflected wave detector generates a measured value of the power level of a component having the same frequency as the set frequency specified from the second frequency specifying signal among all the frequency components of the reflected wave, that is, a measured value P_r21of the power level of the reflected wave. The measured value P_f21is given to the power supply control unit 38e. Further, the reflected wave detector generates a measured value of the total power level of all frequency components of the reflected wave, that is, a measured value P_r22of the power level of the reflected wave. The measured value P_r22is given to the power supply control unit 38e for the protection of the power amplifier 38b.

In the embodiment, the radio-frequency power supply 38 may perform a load power control during the period P1. That is, the radio-frequency power supply 38 may adjust the power level of the radio-frequency power RF2 so that the load power level of the radio-frequency power RF2 in the period P1 approaches or matches the specified target power level. The power supply control unit 38e may control the power amplifier 38b in the load power control of the radio-frequency power supply 38.

In the load power control when the first mode or the third mode is designated, the power supply control unit 38e may control the power amplifier 38b to adjust the power level of the modulated wave MW2 in the first sub-period SP11. The power level of the modulated wave MW2 in the first sub-period SP11 is adjusted so that the load power level PL21 in the monitoring period MP1 approaches or matches the specified target power level.

As described above, the monitoring period MP1 is a period within the first sub-period SP11. The monitoring period MP1 may be a period that starts after a predetermined time length has elapsed from the start time of the first sub-period SP11. The monitoring period MP1 is designated by the main control unit 70. The load power level P_L21is a difference between the power level of the traveling wave of the radio-frequency power RF2 in the monitoring period MP1 and the power level of the reflected wave of the radio-frequency power RF2 in the monitoring period MP1. The load power level P_L21is obtained as the difference between the measured value P_f21and the measured value P_r21during the monitoring period MP1. The load power level P_L21may be obtained as the difference between the average value of the measured value P_f21and the average value of the measured value P_r21during the monitoring period MP1. Alternatively, the load power level P_L21may be obtained as the difference between the moving average value of the measured value P_f21and the moving average value of the measured value P_r21in the plurality of monitoring periods MP1.

When the power level of the modulated wave MW2 in the second sub-period SP12 is not 0 W, the radio-frequency power supply 38 may execute the load power control of the modulated wave MW2 in the second sub-period SP12. In the load power control, the power supply control unit 38e may control the power amplifier 38b to adjust the power level of the modulated wave MW2 in the second sub-period SP12. The power level of the modulated wave MW2 in the second sub-period SP12 is adjusted so that the load power level PL22 in the monitoring period MP2 approaches or matches the specified target power level.

As described above, the monitoring period MP2 may be a period that coincides with the second sub-period SP12. Alternatively, the monitoring period MP2 may be a period within the second sub-period SP12, and may be a period that starts after a predetermined time length has elapsed from the start time of the second sub-period SP12. The monitoring period MP2 is designated by the main control unit 70. The load power level P_L22is a difference between the power level of the traveling wave of the radio-frequency power RF2 in the monitoring period MP2 and the power level of the reflected wave of the radio-frequency power RF2 in the monitoring period MP2. The load power level P_L22is obtained as the difference between the measured value P_f21and the measured value P_r21during the monitoring period MP2. The load power level P_L22may be obtained as the difference between the average value of the measured value P_f21and the average value of the measured value P_r21during the monitoring period MP2. Alternatively, the load power level P_L22may be obtained as the difference between the moving average value of the measured value P_f21and the moving average value of the measured value P_r21in the plurality of monitoring periods MP2.

The radio-frequency power supply 38 may also perform a load power control even when the second mode is designated. In the load power control when the second mode is designated, the power supply control unit 38e may control the power amplifier 38b to adjust the power level of the continuous wave CW2 in the period P1. The power level of the continuous wave CW2 in the period P1 is adjusted so that the average value of the load power level P_L21in the monitoring period MP1 and the load power level P_L22in the monitoring period MP2 matches or approaches the specified target power level.

The matching device 42 is configured to set the load-side impedance of the radio-frequency power supply 38, that is, the load impedance. In each of the first and second modes, the matching device 42 may set the load impedance of the radio-frequency power supply 38 in the period P1 to a target impedance different from the output impedance of the radio-frequency power supply 38. The load impedance of the radio-frequency power supply 38 in the period P1 may be specified by the measured value of the load impedance of the radio-frequency power supply 38 in the monitoring period MP1.

In the second mode, the matching device 42 may match the load impedance of the radio-frequency power supply 38 in the period P1 with the output impedance of the radio-frequency power supply 38. Alternatively, the matching device 42 sets the load impedance of the radio-frequency power supply 38 in the period P1 to a target impedance different from the output impedance of the radio-frequency power supply 38 in the second mode as well as in the first and third modes.

The matching device 42 gradually changes the load impedance of the radio-frequency power supply 38 in the period P2 to the target impedance for the subsequent period PB in each of the first mode and the third mode. That is, the matching device 42 is configured to gradually change the load impedance of the radio-frequency power supply 38 to the target impedance for the subsequent period PB in the period P2 before or after the power generated by the radio-frequency power supply 38 is switched from the power wave W21 to the power wave W22.

As illustrated in FIGS. 8 and 9, in each of the first and third modes, the matching device 42 gradually changes the load impedance of the radio-frequency power supply 38 so that the absolute value |Γ₂| of the reflectance coefficient Γ₂is gradually changed to the set target value for the subsequent period PB in the period P2. As illustrated in FIG. 8, when the subsequent period PB is the period P2 in each of the first and third modes, the set target value of the absolute value |Γ₂| of the reflectance coefficient Γ₂for the subsequent period PB may be zero. As illustrated in FIG. 9, when the subsequent period PB is the period P1 in each of the first and third modes, the set target value of the absolute value |Γ₂| of the reflectance coefficient Γ₂for the subsequent period PB is larger than zero, for example, 0.3 or more and 0.5 or less.

As described above, the subsequent period PB includes a plurality of consecutive sub-period SPs. As described above, the plurality of sub-period SPs include sub-periods SP₁, SP₂, . . . , SP_N. The matching device 42 may gradually change the load impedance of the radio-frequency power supply 38 so that the absolute value |Γ₂| of the reflectance coefficient Γ₂in the period P2 is gradually changed through the sub-periods SP₁, SP₂, . . . , SP_Nto the set target value for the subsequent period PB. As illustrated in FIG. 8, when the subsequent period PB is the period P2, the matching device 42 gradually changes the load impedance of the radio-frequency power supply 38 through the sub-periods SP₁, SP₂, . . . , SP_Nin the period P2 after the start of the subsequent period PB (period P2). As illustrated in FIG. 9, when the subsequent period PB is the period P1, the matching device 42 gradually changes the load impedance of the radio-frequency power supply 38 through the sub-periods SP₁, SP₂, . . . , SP_Nin the period P2 before the start of the subsequent period PB (period P1). The matching device 42 sets the load impedance of the radio-frequency power supply 38 so that the absolute value |Γ₂| of the reflectance coefficient Γ₂in the sub-period SP_(N+1)is set as the set target value for the subsequent period PB.

In the second mode, the matching device 42 may match the load impedance of the radio-frequency power supply 38 in the period P2 with the output impedance of the radio-frequency power supply 38. Further, the matching device 42 may gradually change the load impedance of the radio-frequency power supply 38 in the period P2 to the target impedance for the subsequent period PB in the second mode as well as in the first and third modes.

In the embodiment, the matching device 42 includes a matching circuit 42a, a sensor 42b, a controller 42c, an actuator 42d, and an actuator 42e, as illustrated in FIG. 6. The matching circuit 42a may include a variable reactance element 42g and a variable reactance element 42h. Each of the variable reactance element 42g and the variable reactance element 42h is, for example, a variable capacitor. In addition, the matching circuit 42a may further include an inductor and the like.

The controller 42c operates under the control of the main control unit 70. The controller 42c adjusts the load impedance of the radio-frequency power supply 38 according to the measured value of the load-side impedance (i.e., the load impedance) of the radio-frequency power supply 38 given by the sensor 42b. The controller 42c adjusts the load impedance of the radio-frequency power supply 38 by controlling the actuator 42d and the actuator 42e and adjusting the reactance of each of the variable reactance element 42g and the variable reactance element 42h. The actuator 42d and the actuator 42e are, for example, motors.

The sensor 42b is configured to acquire a measured value of the load impedance of the radio-frequency power supply 38. In the embodiment, the measured value of the load impedance of the radio-frequency power supply 38 is acquired as a moving average value. As illustrated in FIG. 7, the sensor 42b may include a current detector 102B, a voltage detector 104B, filters 106B and 108B, average value calculators 110B and 112B, moving average value calculators 114B and 116B, and an impedance calculator 118B.

The voltage detector 104A detects the voltage waveform of the radio-frequency power RF2 transmitted on the power feeding line 45, and outputs a voltage waveform analog signal representing the voltage waveform. This voltage waveform analog signal is input to the filter 106B. The filter 106B generates a voltage waveform digital signal by digitizing the input voltage waveform analog signal. The filter 106B receives the above-mentioned second frequency specifying signal from the power supply control unit 38e and extracts only the frequency component corresponding to the frequency specified by the second frequency specifying signal from the voltage waveform digital signal, thereby generating a filtration voltage waveform signal. The filter 106B may be composed of an FPGA.

The filtration voltage waveform signal generated by the filter 106A is output to the average value calculator 110B. The average value calculator 110B receives a monitoring period setting signal from the main control unit 70. The average value calculator 110B obtains the average value of the voltage within the period specified from the monitoring period setting signal from the filtration voltage waveform signal. The average value calculator 110B obtains the average value V_B11of the voltage in each monitoring period MP1 as the average value of the voltage. When the second mode is designated, the average value calculator 110B may further obtain the average value V_B12of the voltage in each monitoring period MP2 as the average value of the voltage. Further, the average value calculator 110B may be composed of, for example, an FPGA.

The moving average value calculator 114B obtains the moving average value V_MB11of the average value V_B11which is obtained from the voltage of the radio-frequency power RF2 in the latest and predetermined number of monitoring periods MP1 among the plurality of average values V_B11already obtained. The moving average value V_MB11is output to the impedance calculator 118B.

In the second mode, the moving average value calculator 114B may further obtain the moving average value V_MB12of the average value V_B12which is obtained from the voltage of the radio-frequency power RF2 in the latest and predetermined number of monitoring periods MP2 among the plurality of average values V_B12already obtained. The moving average value V_MB12is output to the impedance calculator 118B.

The current detector 102B detects the current waveform of the radio-frequency power RF2 transmitted on the power feeding line 45, and outputs a current waveform analog signal representing the current waveform. This voltage waveform analog signal is input to the filter 108B. The filter 108B generates a voltage waveform digital signal by digitizing the input voltage waveform analog signal. The filter 108B receives the above-mentioned second frequency specifying signal from the power supply control unit 38e and extracts only the frequency component corresponding to the frequency specified by the second frequency specifying signal from the voltage waveform digital signal, thereby generating a filtration voltage waveform signal. The filter 108B may be composed of an FPGA.

The filtration voltage waveform signal generated by the filter 108B is output to the average value calculator 112B. The average value calculator 112B receives a monitoring period setting signal from the main control unit 70. The average value calculator 112B obtains the average value of the current within the period specified from the monitoring period setting signal from the filtration current waveform signal. The average value calculator 112B obtains the average value I_B11of the current in the monitoring period MP1 in each period P1 as the average value of the current. When the second mode is designated, the average value calculator 112B may further obtain the average value I_B12of the current in each monitoring period MP2 as the average value of the current. Further, the average value calculator 112B may be composed of, for example, an FPGA.

The moving average value calculator 116B obtains the moving average value I_MB11of the average value I_B11which is obtained from the current of the radio-frequency power RF2 in the latest and predetermined number of monitoring periods MP1 among the plurality of average values I_B11already obtained. The moving average value I_MB11is output to the impedance calculator 118B.

In the second mode, the moving average value calculator 116B may further obtain the moving average value I_MB12of the average value I_B12which is obtained from the current of the radio-frequency power RF2 in the latest and predetermined number of monitoring periods MP2 among the plurality of average values I_B12already obtained. The moving average value I_MB12is output to the impedance calculator 118B.

The impedance calculator 118A obtains the moving average value Z_MB11of the load impedance of the radio-frequency power supply 38 from the moving average value I_MB11and the moving average value V_MB11. The moving average value Z_MB11is a measured value of the load impedance of the radio-frequency power supply 38 during the monitoring period MP1. In the second mode, the impedance calculator 118B may further obtain the moving average value Z_MB12of the load impedance of the radio-frequency power supply 38 from the moving average value I_MB12and the moving average value V_MB12. The moving average value Z_MB12is a measured value of the load impedance of the radio-frequency power supply 38 during the monitoring period MP2.

The controller 42c controls the matching circuit 42a in order to set the load impedance of the radio-frequency power supply 38. In the embodiment, the controller 42c sets the load impedance of the radio-frequency power supply 38 by adjusting the reactances of the variable reactance element 42g and the variable reactance element 42h through the actuator 42d and the actuator 42e.

In each of the first and third modes, the controller 42c adjusts the load impedance of the radio-frequency power supply 38 in the period P1 specified by the moving average value Z_MB11to a target impedance different from the output impedance of the radio-frequency power supply 38.

In the embodiment, the controller 42c may specify the target impedance from the set target value of the absolute value |Γ₂| of the reflectance coefficient Γ₂of the radio-frequency power RF2 in the period P1. The set target value of the absolute value |Γ₂| in the period P1 may be a value larger than 0. For example, the set target value of the absolute value |Γ₂| in the period P1 is 0.3 or more and 0.5 or less. The reflectance coefficient Γ₂is defined by the following equation (2).

Γ₂=(Z₂−Z₀₂)/(Z₂+Z₀₂) (2)

In the equation (2), Z₀₂is the characteristic impedance of the power feeding line 45, and is generally 50Ω. In the equation (2), Z₂is the target impedance. The controller 42c determines the target impedance Z₂corresponding to the set target value of the absolute value |Γ₂| in the period P1 based on the equation (2). The controller 42c sets the load impedance of the radio-frequency power supply 38 so that the load impedance of the radio-frequency power supply 38 during the period P1 specified by the moving average value Z_MB11approaches or matches the target impedance Z₂.

When the second mode is designated, the controller 42c may match the load impedance of the radio-frequency power supply 38 with the output impedance (matching point) of the radio-frequency power supply 38 during the period P1. The load impedance of the radio-frequency power supply 38 may be specified by the average value of the moving average value Z_MB11and the moving average value Z_MB12. Alternatively, the controller 42c may adjust the load impedance of the radio-frequency power supply 38 in the period P1 to a target impedance different from the output impedance of the radio-frequency power supply 38 in the second mode as well as in the first and third modes.

As described above, in each of the first and third modes, the matching device 42 may gradually change the load impedance of the radio-frequency power supply 38 so that the absolute value |Γ₂| of the reflectance coefficient Γ₂is gradually changed to the set target value for the subsequent period PB. As described above, the matching device 42 gradually changes the load impedance of the radio-frequency power supply 38 through a plurality of sub-periods SPs in the period P2.

The target values of the absolute value |Γ₂| of the reflectance coefficient Γ₂of the radio-frequency power RF2 in the plurality of sub-periods SP₁, SP₂, . . . , SP_Nare different from each other. Of any two consecutive sub-periods included in the plurality of sub-periods SP2, the difference between the target value of the absolute value |Γ₂| of the reflectance coefficient Γ₂in one sub-period and the target value of the absolute value |Γ₂| of the reflectance coefficient Γ₂in the other period is ΔΓ₂. In addition, FIG. 8 and FIG. 9 illustrate ΔΓ₂as ΔΓ. As illustrated in FIG. 8, when the subsequent period PB is the period P2, the target value of the absolute value |Γ₂| of the reflectance coefficient Γ₂in the sub-period SP_(N+1), that is, the set target value is zero. As illustrated in FIG. 9, when the subsequent period PB is the period P1, the target value of the absolute value |Γ₂| of the reflectance coefficient Γ₂in the sub-period SP_(N+1), that is, the set target value is larger than zero, for example, 0.3 or more and 0.5 or less. In the embodiment, the TL may be set to 0.5 seconds or more and the ΔΓ₂may be set to 0.2 or less. Further, the TL may be set to 0.2 seconds or more and the ΔΓ₂may be set to 0.1 or less. Further, the TL may be set to 0.5 seconds or more and the ΔΓ₂may be set to 0.05 or less.

The controller 42c sets the load impedance of the radio-frequency power supply 38. Specifically, the controller 42c adjusts the load impedance of the radio-frequency power supply 38 in the sub-period SP_ifrom the target value of the absolute value |Γ₂| of the reflectance coefficient Γ₂of the radio-frequency power RF2 in the sub-period SP_ito the target impedance Z₂specified based on the equation (2). Further, the controller 42c may specify the load impedance of the radio-frequency power supply 38 in the sub-period SP_ifrom the measured value of the load impedance of the radio-frequency power supply 38 obtained by the sensor 42b. The sensor 42b may obtain the measured value of the load impedance of the radio-frequency power supply 38 from the above-mentioned filtration voltage waveform signal and filtration current waveform signal.

When the second mode is designated, the controller 42c may match the load impedance of the radio-frequency power supply 38 with the output impedance (matching point) of the radio-frequency power supply 38 during the period P2. In the second mode as well as in the first and third modes, the controller 42c may gradually change the load impedance of the radio-frequency power supply 38 to the target impedance for the subsequent period PB in the period P2.

In the plasma processing apparatus 1, the matching device 40 gradually changes the load impedance to the target impedance for the subsequent period during the period in which the continuous wave CW1 is supplied before or after the power supplied from the radio-frequency power supply 36 is switched from the power wave W11 to the power wave W12. Thus, the matching device 40 may follow the change in the load impedance to be set after the power from the radio-frequency power supply 36 is switched from the power wave W11 to the power wave W12. Therefore, it is possible to reduce the reflection of the power supplied from the radio-frequency power supply 36 after being switched from the power wave W11 to the power wave W12. Further, the matching device 42 gradually changes the load impedance to the target impedance for the subsequent period during the period in which the continuous wave CW2 is supplied before or after the power supplied from the radio-frequency power supply 38 is switched from the power wave W21 to the power wave W22. Thus, the matching device 42 may follow the change in the load impedance to be set after the power from the radio-frequency power supply 38 is switched from the power wave W21 to the power wave W22. Therefore, it is possible to reduce the reflection of the power supplied from the radio-frequency power supply 38 after being switched from the power wave W21 to the power wave W22.

In the embodiment, the matching device 40 adjusts the load impedance of the radio-frequency power supply 36 in the period P1 to a target impedance different from the output impedance of the radio-frequency power supply 36. According to this embodiment, the reflection from the load on the modulated wave MW1 may be reduced during the period P1. In the embodiment, in each of the first and third modes, the matching device 42 adjusts the load impedance of the radio-frequency power supply 38 in the period P1 to a target impedance different from the output impedance of the radio-frequency power supply 38. According to this embodiment, the reflection from the load on the modulated wave MW2 may be reduced during the period P1.

In the embodiment, a load power control of the modulated wave MW1 may be performed during the period P1. According to this embodiment, even when a reflection occurs due to the target impedance being different from the output impedance of the radio-frequency power supply 36 in the period P1, the modulated wave MW1 of the target power level may be coupled to the plasma. In the embodiment, a load power control of the modulated wave MW2 may be performed during the period P1. According to this embodiment, even when a reflection occurs due to the target impedance being different from the output impedance of the radio-frequency power supply 38 in the period P1, the modulated wave MW2 of the target power level may be coupled to the plasma.

Hereinafter, FIG. 10 will be referenced. FIG. 10 is a flowchart of a matching method according to the embodiment. In the matching method illustrated in FIG. 10 (hereinafter, referred to as a “method MT”), the power supplied from at least one of the radio-frequency power supply 36 and the radio-frequency power supply 38 is switched from the power wave of one of the continuous wave and the modulated wave to the power wave of the other. That is, in the method MT, the power wave W11 is supplied from the radio-frequency power supply 36, and the power wave W21 is supplied from the radio-frequency power supply 38. Next, at least one of the power wave W12 from the radio-frequency power supply 36 and the power wave W22 from the radio-frequency power supply 38 is supplied. The power wave W11 may be supplied from the radio-frequency power supply 36 for two consecutive periods, or the power wave W21 may be supplied from the radio-frequency power supply 36 for two consecutive periods. In the method MT, the power supplied from at least one of the radio-frequency power supply 36 and the radio-frequency power supply 38 may be alternately switched from the power wave of one of the continuous wave and the modulated wave to the power wave of the other.

The method MT is started in step ST1. In step ST1, the power wave W11 is supplied from the radio-frequency power supply 36, and the power wave W21 is supplied from the radio-frequency power supply 38. During the execution of step ST1, the load impedance of the radio-frequency power supply 36 is set by the matching device 40. When the power wave W11 is the modulated wave MW1, the load impedance of the radio-frequency power supply 36 may be adjusted to a target impedance different from the output impedance of the radio-frequency power supply 36 as described above during the execution of step ST1. Further, when the power wave W11 is the modulated wave MW1, the load power control may be executed by the radio-frequency power supply 36 as described above during the execution of step ST1.

When the power wave W11 is the continuous wave CW1, the load impedance of the radio-frequency power supply 36 may be matched with the output impedance of the radio-frequency power supply 36 during the execution of step ST1. Further, when the power wave W11 is the continuous wave CW1, similar to the case where the power wave W11 is the modulated wave MW1, the load impedance of the radio-frequency power supply 36 may be adjusted to a target impedance different from the output impedance of the radio-frequency power supply 36 during the execution of step ST1.

During the execution of step ST1, the load impedance of the radio-frequency power supply 38 is set by the matching device 42. When the power wave W21 is the modulated wave MW2, the load impedance of the radio-frequency power supply 38 may be adjusted to a target impedance different from the output impedance of the radio-frequency power supply 38 as described above during the execution of step ST1. Further, when the power wave W21 is the modulated wave MW2, the load power control may be executed by the radio-frequency power supply 38 as described above during the execution of step ST1.

When the power wave W21 is the continuous wave CW2, the load impedance of the radio-frequency power supply 38 may be matched with the output impedance of the radio-frequency power supply 38 during the execution of step ST1. Further, when the power wave W21 is the continuous wave CW2, similar to the case where the power wave W21 is the modulated wave MW2, the load impedance of the radio-frequency power supply 36 may be adjusted to a target impedance different from the output impedance of the radio-frequency power supply 36 during the execution of step ST1.

In step STJa, it is determined whether the power wave supplied in the preceding period PA out of the two consecutive periods is a continuous wave. When the continuous wave CW1 is not supplied in the preceding period PA, that is, when the modulated wave MW1 is supplied, step STA2 is executed in the succeeding period PB of the two consecutive periods. When the modulated wave MW1 is supplied in the preceding period PA and the continuous wave CW1 is supplied in the subsequent period PB, step STA3 is executed in the subsequent period PB. When the continuous wave CW1 is not supplied in the preceding period PA, step STAB is executed in the subsequent period PB. When the modulated wave CW1 is supplied in the preceding period PA and the continuous wave MW1 is supplied in the subsequent period PB, step STA2 is executed in the preceding PB.

When the continuous wave CW2 is not supplied in the preceding period PA, that is, when the modulated wave MW2 is supplied, step STA2 is executed in the subsequent period PB. When the modulated wave MW2 is supplied in the preceding period PA and the continuous wave CW2 is supplied in the subsequent period PB, step STA3 is executed in the subsequent period PB. When the continuous wave CW2 is not supplied in the preceding period PA, step STB3 is executed in the subsequent period PB. When the modulated wave CW2 is supplied in the preceding period PA and the continuous wave MW2 is supplied in the subsequent period PB, step STB2 is executed in the preceding PB.

Step STA2 is executed when the modulated wave MW1 is supplied in the preceding period PA. In step STA2, the power wave of the subsequent period PB is supplied from the radio-frequency power supply 36. When the power wave supplied from the radio-frequency power supply 36 in step STA2 is the continuous wave CW1, the load impedance of the radio-frequency power supply 36 is gradually changed in step STA3 after the start of the subsequent period PB to the target impedance for the subsequent period PB as described above. When the power wave supplied from the radio-frequency power supply 36 in step STA2 is the modulated wave MW1, the load impedance of the radio-frequency power supply 36 may be set to a target impedance different from the output impedance of the radio-frequency power supply 36.

Step STA2 is executed when the modulated wave MW2 is supplied in the preceding period PA. In step STA2, the power wave of the subsequent period PB is supplied from the radio-frequency power supply 38. When the power wave supplied from the radio-frequency power supply 38 in step STA2 is the continuous wave CW2, the load impedance of the radio-frequency power supply 38 is gradually changed in step STA3 after the start of the subsequent period PB to the target impedance for the subsequent period PB as described above. When the power wave supplied from the radio-frequency power supply 38 in step STA2 is the modulated wave MW2, the load impedance of the radio-frequency power supply 38 may be set to a target impedance different from the output impedance of the radio-frequency power supply 38.

When the continuous wave CW1 is not supplied in the preceding period PA, step STB3 is executed in the subsequent period PB. In step STB3, the power wave of the subsequent period PB is supplied from the radio-frequency power supply 36. When the power wave supplied from the radio-frequency power supply 36 in step STB3 is the modulated wave MW1, step STB2 is executed in the preceding period PA before the start of the subsequent period PB. In step STB2, the load impedance of the radio-frequency power supply 36 is gradually changed to the target impedance for the subsequent period PB as described above. When the power wave supplied from the radio-frequency power supply 36 in step STB3 is the modulated wave CW1, the load impedance of the radio-frequency power supply 36 may be set to a target impedance different from the output impedance of the radio-frequency power supply 36.

When the continuous wave CW2 is not supplied in the preceding period PA, step STB3 is executed in the subsequent period PB. In step STB3, the power wave of the subsequent period PB is supplied from the radio-frequency power supply 38. When the power wave supplied from the radio-frequency power supply 38 in step STB3 is the modulated wave MW