阅读说明：本技术 高频电源装置以及高频功率的输出方法 (High-frequency power supply device and high-frequency power output method ) 是由 深野胜之 中森雄哉 板谷耕司 滨石悟 于 2020-09-14 设计创作，主要内容包括：本发明提供高频电源装置以及高频功率的输出方法。提供能缓和高频功率的急变的高频电源装置以及高频功率的输出方法。高频电源装置生成高频信号,周期性地控制生成的高频信号的振幅或相位,输出基于振幅或相位被控制的高频信号从而大小被控制的高频功率。高频电源装置控制高频信号的振幅或相位,使得高频功率的大小在控制周期中的第1期间成为第1水平,在与第1期间不同的控制周期中的第2期间成为比第1水平低的第2水平。高频电源装置使第1期间的长度相对于控制周期的长度的比以及第2水平的至少一方渐减或渐增,并使第1水平渐增或渐减。(The invention provides a high-frequency power supply device and a high-frequency power output method. Provided are a high-frequency power supply device and a high-frequency power output method capable of alleviating a sudden change in high-frequency power. The high-frequency power supply device generates a high-frequency signal, periodically controls the amplitude or phase of the generated high-frequency signal, and outputs high-frequency power whose magnitude is controlled based on the high-frequency signal whose amplitude or phase is controlled. The high-frequency power supply device controls the amplitude or phase of the high-frequency signal so that the magnitude of the high-frequency power becomes the 1 st level in the 1 st period in the control period, and becomes the 2 nd level lower than the 1 st level in the 2 nd period in the control period different from the 1 st period. The high-frequency power supply device gradually decreases or gradually increases at least one of the ratio of the length of the 1 st period to the length of the control period and the 2 nd level, and gradually increases or decreases the 1 st level.)

1. A high-frequency power supply device is characterized by comprising:

a high-frequency generation unit for generating a high-frequency signal;

a control unit for periodically controlling the amplitude or phase of the high-frequency signal generated by the high-frequency generation unit; and

a high frequency output unit for outputting high frequency power of which the magnitude is controlled based on the high frequency signal of which the amplitude or phase is controlled by the control unit,

the control unit controls the amplitude or phase of the high-frequency signal so that the high-frequency power output by the high-frequency output unit has a level 1 in a 1 st period in a control period and has a level 2 lower than the level 1 in a 2 nd period in the control period different from the 1 st period,

the control unit gradually decreases or increases at least one of a ratio of the length of the 1 st period to the length of the control period and the 2 nd level,

the control unit increases the 1 st level so that an average value of the high-frequency power output by the high-frequency output unit is constant, when at least one of the ratio and the 2 nd level is decreased,

the control unit gradually decreases the 1 st level so that an average value of the high-frequency power output by the high-frequency output unit is constant, when at least one of the ratio and the 2 nd level is increased.

2. The high-frequency power supply apparatus according to claim 1,

the high-frequency generation unit generates a plurality of high-frequency signals including a 1 st high-frequency signal and a 2 nd high-frequency signal having the same frequency,

the control unit controls a phase difference between the 1 st high-frequency signal and the 2 nd high-frequency signal in each of the 1 st period and the 2 nd period,

the high-frequency output unit includes:

a 1 st generation unit that generates a 1 st high-frequency voltage having a phase corresponding to the 1 st high-frequency signal;

a 2 nd generating unit that generates a 2 nd high-frequency voltage having a phase corresponding to the 2 nd high-frequency signal; and

and a power combining unit that combines radio frequency powers based on the 1 st radio frequency voltage and the 2 nd radio frequency voltage generated by the 1 st generation unit and the 2 nd generation unit in a ratio corresponding to the phase difference.

3. The high-frequency power supply apparatus according to claim 1,

the control unit controls the amplitude of the high-frequency signal in each of the 1 st period and the 2 nd period,

the high-frequency output unit outputs high-frequency power having a magnitude corresponding to the high-frequency signal whose amplitude is controlled by the control unit.

4. A high-frequency power supply device according to any one of claims 1 to 3,

the high-frequency power supply device further includes: a power detection unit for detecting the high-frequency power outputted from the high-frequency output unit,

the control unit adjusts the amplitude or phase of the high-frequency signal so that the magnitude of the high-frequency power detected by the power detection unit coincides with the 1 st level and the 2 nd level in the 1 st period and the 2 nd period.

5. A high-frequency power supply device is characterized by comprising:

a high frequency generation unit for generating a 1 st high frequency signal and a 2 nd high frequency signal;

a control unit for periodically controlling the amplitudes or phases of the 1 st high-frequency signal and the 2 nd high-frequency signal generated by the high-frequency generation unit;

a 1 st high-frequency output unit that outputs a 1 st high-frequency signal whose amplitude or phase is controlled by the control unit, thereby controlling the magnitude of the high-frequency power; and

a 2 nd high frequency output unit for outputting a high frequency power whose magnitude is controlled based on the 2 nd high frequency signal whose amplitude or phase is controlled by the control unit,

the control unit controls the amplitude or phase of the 1 st high-frequency signal so that the magnitude of the high-frequency power output from the 1 st high-frequency output unit becomes the 1 st level in the 1 st period in the control cycle,

the control unit controls the amplitude or phase of the 2 nd high-frequency signal so that the magnitude of the high-frequency power output by the 2 nd high-frequency output unit becomes a 2 nd level lower than the 1 st level in a 2 nd period in the control period different from the 1 st period,

the control unit gradually decreases or increases at least one of a ratio of the length of the 1 st period to the length of the control period and the 2 nd level,

the control unit increases the 1 st level by gradually increasing the 1 st level so that an average value of the sum of the high-frequency powers output from the 1 st high-frequency output unit and the 2 nd high-frequency output unit is constant when at least one of the ratio and the 2 nd level is gradually decreased,

the control unit gradually decreases the 1 st level so that an average value of a sum of the high-frequency powers output from the 1 st high-frequency output unit and the 2 nd high-frequency output unit is constant, when increasing at least one of the ratio and the 2 nd level.

6. A high frequency power output method for outputting a high frequency power whose magnitude is controlled based on a high frequency signal whose amplitude or phase is periodically controlled,

controlling the amplitude or phase of the high-frequency signal so that the magnitude of the high-frequency power becomes a 1 st level in a 1 st period in a control period and becomes a 2 nd level lower than the 1 st level in a 2 nd period in the control period different from the 1 st period,

gradually decreasing or increasing at least one of a ratio of the length of the 1 st period to the length of the control period and the 2 nd level,

increasing the 1 st level so that the average value of the high-frequency power is constant when at least one of the ratio and the 2 nd level is decreased,

when at least one of the ratio and the 2 nd level is increased, the 1 st level is decreased gradually so that the average value of the high-frequency power becomes constant.

Technical Field

The present disclosure relates to a high-frequency power supply device for supplying high-frequency power to a plasma processing apparatus and a method for outputting high-frequency power.

Background

There are various methods of supplying high-frequency power to a plasma processing apparatus used in the manufacture of semiconductor devices and the like. In the 1 st mode, the high-frequency power of a relatively high frequency suitable for the generation of plasma is supplied from the 1 st power supply to the upper electrode. Further, a high-frequency power of a relatively low frequency suitable for the attraction of ions in the plasma in the object to be processed is supplied from the 2 nd power supply to the lower electrode.

Hereinafter, the Onset (ON) or high level is collectively referred to as the 1 st level, and the Offset (OFF) or low level is collectively referred to as the 2 nd level. Patent document 1 proposes a technique for suppressing charging damage to a target substrate. In this technique, the high-frequency power of the 1 st power supply is amplitude-offset modulated to the 1 st level/2 nd level at a given frequency to shorten the time for continuously generating plasma. Thereby suppressing charging damage to the substrate to be processed. Further, the high-frequency power of the 2 nd power supply is modulated to the 1 st level/the 2 nd level at the 2 nd frequency to interrupt the time when the etching of the predetermined film on the substrate progresses. This reduces the so-called micro-loading effect and enables etching at a high etching rate (etching amount per hour).

On the other hand, the processing conditions such as the plasma state are sequentially switched in each processing step according to a so-called recipe. For example, when plasma is intermittently generated, the magnitude of high-frequency power for generating plasma is periodically modulated to the 1 st level/the 2 nd level (see patent document 2).

Documents of the prior art

Patent document

Patent document 1: JP 2015-A90759

Patent document 2: JP patent laid-open publication No. 2013-214583

However, according to the techniques disclosed in patent documents 1 and 2, the high frequency power discontinuously changes from a non-modulated state to an amplitude offset modulated state. The magnitude of the high-frequency power is changed stepwise from the 1 st level and the 2 nd level to the 3 rd level and the 4 th level. For this reason, the conditions for generating ions and radicals in the plasma may change abruptly, and the plasma may become unstable.

Disclosure of Invention

The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a high-frequency power supply device and a high-frequency power output method capable of alleviating a sudden change in high-frequency power.

A high-frequency power supply device according to an aspect of the present disclosure includes: a high-frequency generation unit for generating a high-frequency signal; a control unit for periodically controlling the amplitude or phase of the high-frequency signal generated by the high-frequency generation unit; and a high-frequency output unit that outputs high-frequency power whose magnitude is controlled based on the high-frequency signal whose amplitude or phase is controlled by the control unit, wherein the control unit controls the amplitude or phase of the high-frequency signal such that the magnitude of the high-frequency power output by the high-frequency output unit becomes a 1 st level in a 1 st period in a control cycle and becomes a 2 nd level lower than the 1 st level in a 2 nd period in the control cycle different from the 1 st period, the control unit gradually decreases or increases at least one of a ratio of a length of the 1 st period to a length of the control cycle and the 2 nd level, the control unit gradually increases the 1 st level such that an average value of the high-frequency power output by the high-frequency output unit is constant when at least one of the ratio and the 2 nd level is gradually decreased, and the control unit gradually increases at least one of the ratio and the 2 nd level, the 1 st level is gradually decreased so that the average value of the high-frequency power output from the high-frequency output unit is constant.

A high-frequency power output method according to an aspect of the present disclosure outputs high-frequency power whose magnitude is controlled based on a high-frequency signal whose amplitude or phase is periodically controlled, controls the amplitude or phase of the high-frequency signal such that the magnitude of the high-frequency power becomes a 1 st level in a 1 st period in a control period, and becomes a 2 nd level lower than the 1 st level in a 2 nd period in the control period different from the 1 st period, gradually decreases or increases at least one of a ratio of a length of the 1 st period to a length of the control period and the 2 nd level, and when at least one of the ratio and the 2 nd level is gradually decreased, the 1 st level is gradually increased such that an average value of the high-frequency power is fixed, and when at least one of the ratio and the 2 nd level is gradually increased, the 1 st level is gradually decreased so that the average value of the high-frequency power becomes fixed.

In this embodiment, the control unit periodically controls the amplitude or phase of the high-frequency signal generated by the high-frequency generation unit, thereby periodically adjusting the magnitude of the high-frequency power output by the high-frequency output unit to the 1 st level and the 2 nd level in each of the 1 st period and the 2 nd period. The 2 nd level is lower than the 1 st level. The control unit further gradually decreases or increases at least one of a duty ratio of the 1 st period with respect to the control period and the 2 nd level, and gradually increases or decreases the 1 st level, while periodically controlling the amplitude or the phase of the high-frequency signal. Thus, the average value of the high-frequency power output by the high-frequency output unit is kept constant. That is, the control unit increases the 1 st level when at least one of the duty ratio and the 2 nd level is decreased. The control unit gradually decreases the 1 st level when at least one of the duty ratio and the 2 nd level is increased. Thereby, the average value of the high-frequency power is kept constant.

In a high-frequency power supply device according to an aspect of the present disclosure, the high-frequency generation unit generates a plurality of high-frequency signals including a 1 st high-frequency signal and a 2 nd high-frequency signal having the same frequency, the control unit controls a phase difference between the 1 st high-frequency signal and the 2 nd high-frequency signal in each of the 1 st period and the 2 nd period, and the high-frequency output unit includes: a 1 st generation unit that generates a 1 st high-frequency voltage having a phase corresponding to the 1 st high-frequency signal; a 2 nd generating unit that generates a 2 nd high-frequency voltage having a phase corresponding to the 2 nd high-frequency signal; and a power combining unit that combines radio frequency powers based on the 1 st radio frequency voltage and the 2 nd radio frequency voltage generated by the 1 st generation unit and the 2 nd generation unit in a ratio corresponding to the phase difference.

In this aspect, the high-frequency generation unit generates the 1 st high-frequency signal and the 2 nd high-frequency signal having the same frequency. The control unit individually controls the phase difference between the 1 st high-frequency signal and the 2 nd high-frequency signal in each of the 1 st period and the 2 nd period. The high-frequency output unit generates a 1 st high-frequency voltage having a phase corresponding to the 1 st high-frequency signal, and generates a 2 nd high-frequency voltage having a phase corresponding to the 2 nd high-frequency signal. The high-frequency output unit further combines the high-frequency powers based on the generated 1 st high-frequency voltage and 2 nd high-frequency voltage at a ratio corresponding to a phase difference between the 1 st high-frequency voltage and the 2 nd high-frequency voltage, and outputs the combined high-frequency powers. By combining radio frequency powers based on the 1 st radio frequency voltage and the 2 nd radio frequency voltage at different ratios in the 1 st period and the 2 nd period, the magnitudes of the radio frequency powers output in the 1 st period and the 2 nd period are changed to the 1 st level and the 2 nd level, respectively.

In the high-frequency power supply device according to one aspect of the present disclosure, the control unit controls the amplitude of the high-frequency signal in each of the 1 st period and the 2 nd period, and the high-frequency output unit outputs high-frequency power having a magnitude corresponding to the high-frequency signal whose amplitude is controlled by the control unit.

In this aspect, the control unit controls the amplitude of the high-frequency signal generated by the high-frequency generation unit in each of the 1 st period and the 2 nd period. The high-frequency output unit generates high-frequency power having a magnitude corresponding to the amplitude-controlled high-frequency signal. Thus, the magnitudes of the high-frequency power output in each of the 1 st period and the 2 nd period are changed to the 1 st level and the 2 nd level.

In a high-frequency power supply device according to an aspect of the present disclosure, the high-frequency power supply device further includes: and a power detection unit that detects the high-frequency power output by the high-frequency output unit, wherein the control unit adjusts the amplitude or phase of the high-frequency signal so that the magnitude of the high-frequency power detected by the power detection unit coincides with the 1 st level and the 2 nd level in the 1 st period and the 2 nd period.

In this embodiment, the high-frequency power output from the high-frequency output unit is detected in each of the 1 st period and the 2 nd period. The control unit controls the amplitude or phase of the high-frequency signal so that the magnitude of the detected high-frequency power matches the 1 st level and the 2 nd level, which are target values of high-frequency power to be output by the high-frequency output unit in each of the 1 st period and the 2 nd period. As a result, the magnitude of the high-frequency power output in each control period is correctly adjusted.

A high-frequency power supply device according to an aspect of the present disclosure includes: a high frequency generation unit for generating a 1 st high frequency signal and a 2 nd high frequency signal; a control unit for periodically controlling the amplitudes or phases of the 1 st high-frequency signal and the 2 nd high-frequency signal generated by the high-frequency generation unit; a 1 st high-frequency output unit that outputs a 1 st high-frequency signal whose amplitude or phase is controlled by the control unit, thereby controlling the magnitude of the high-frequency power; and a 2 nd high-frequency output unit that outputs high-frequency power whose magnitude is controlled based on a 2 nd high-frequency signal whose amplitude or phase is controlled by the control unit, the control unit controlling the amplitude or phase of the 1 st high-frequency signal so that the magnitude of the high-frequency power output by the 1 st high-frequency output unit becomes a 1 st level in a 1 st period in a control cycle, the control unit controlling the amplitude or phase of the 2 nd high-frequency signal so that the magnitude of the high-frequency power output by the 2 nd high-frequency output unit becomes a 2 nd level lower than the 1 st level in a 2 nd period in the control cycle different from the 1 st period, the control unit gradually decreasing or increasing at least one of a ratio of a length of the 1 st period to a length of the control cycle and the 2 nd level, the control unit gradually decreasing at least one of the ratio and the 2 nd level, the control unit gradually increases the 1 st level so that an average value of a sum of the high-frequency powers output from the 1 st high-frequency output unit and the 2 nd high-frequency output unit is constant, and gradually decreases the 1 st level so that an average value of a sum of the high-frequency powers output from the 1 st high-frequency output unit and the 2 nd high-frequency output unit is constant when at least one of the ratio and the 2 nd level is increased.

In this embodiment, the control unit periodically controls the amplitudes or phases of the 1 st high-frequency signal and the 2 nd high-frequency signal generated by the high-frequency generation unit. The 1 st high-frequency output unit outputs high-frequency power based on the 1 st high-frequency signal whose amplitude or phase is controlled. The 2 nd high-frequency output unit outputs high-frequency power based on the 2 nd high-frequency signal whose amplitude or phase is controlled. The magnitude of the high-frequency power output from the 1 st high-frequency output unit is periodically adjusted to the 1 st level in the 1 st period. The magnitude of the high-frequency power output from the 2 nd high-frequency output unit is periodically adjusted to the 2 nd level in the 2 nd period. The 2 nd level is lower than the 1 st level. The control unit further gradually decreases or increases at least one of the duty ratio of the 1 st period with respect to the control period and the 2 nd level, and gradually increases or decreases the 1 st level, while periodically controlling the amplitudes or phases of the 1 st and 2 nd high-frequency signals. Thus, the average value of the sum of the high-frequency powers output from the 1 st high-frequency output unit and the 2 nd high-frequency output unit is kept constant. That is, the control unit increases the 1 st level when at least one of the duty ratio and the 2 nd level is decreased. The control unit gradually decreases the 1 st level when at least one of the duty ratio and the 2 nd level is increased. Thereby, the average value of the sum of the high frequency powers is kept constant.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present disclosure, a sudden change in high-frequency power can be alleviated.

Drawings

Fig. 1 is a block diagram showing a configuration example of a high-frequency power supply device according to embodiment 1.

Fig. 2 is a circuit diagram showing a configuration example of the power combining unit.

Fig. 3 is an explanatory diagram suitably illustrating the high-frequency power in the case where the 1 st period is gradually decreased in the high-frequency power supply device according to embodiment 1.

Fig. 4 is a graph showing a correspondence relationship between a duty ratio and a phase difference used in the high-frequency power supply device according to embodiment 1.

Fig. 5 is a flowchart showing a processing procedure of the control unit for setting the duty ratio and the phase difference in the pulse generation unit and the high frequency generation unit, respectively.

Fig. 6 is an explanatory diagram schematically showing the high-frequency power in the case where the 1 st period is gradually decreased in the high-frequency power supply device according to modification 1.

Fig. 7 is a graph showing a correspondence relationship between a duty ratio and a phase difference used in the high-frequency power supply device according to modification 1.

Fig. 8 is an explanatory diagram schematically showing the high-frequency power in the case where the 2 nd level is gradually decreased in the high-frequency power supply device according to modification 2.

Fig. 9 is a graph showing a correspondence relationship between a duty ratio and a phase difference used in the high-frequency power supply device according to modification 2.

Fig. 10 is a block diagram showing a configuration example of the high-frequency power supply device according to embodiment 2.

Fig. 11 is a flowchart showing a processing procedure of the control unit for setting the duty ratio and the pulse level to the pulse generating unit.

Fig. 12 is a block diagram showing a configuration example of the high-frequency power supply device according to embodiment 3.

Description of reference numerals

100. 100b, 100c high-frequency power supply device

1. 1b, 1c high frequency generating part

2. 2b, 2c control unit

3 high frequency output unit

30 DC power supply

31. 32 DC-RF converter

33 power combining part

R resistor

N1, N2 input ports

Ns summing port

Tt transmission transformer

34 filter circuit

4 pulse generating part

5 Power detection part

6 high frequency oscillator

7. 7b pulse generating part

8 multiplication arithmetic unit

9 high frequency output unit

200 matcher

300 load

301. 302 electrode

Detailed Description

The present disclosure is described in detail below based on the drawings showing embodiments thereof.

(embodiment mode 1)

Fig. 1 is a block diagram showing a configuration example of a high-frequency power supply device 100 according to embodiment 1. The high-frequency power supply device 100 includes a high-frequency generation unit 1, a control unit 2, and a high-frequency output unit 3. The high frequency generator 1 generates high frequency signals S1 and S2 having the same frequency. The high frequency signals S1 and S2 correspond to the 1 st high frequency signal and the 2 nd high frequency signal, respectively. The control unit 2 controls the phases of the high-frequency signals S1 and S2 generated by the high-frequency generation unit 1. The high-frequency output unit 3 outputs high-frequency power Ps whose magnitude is adjusted based on the high-frequency signals S1 and S2 whose phases are controlled.

The high-frequency power supply device 100 further includes a pulse generation unit 4 and a power detection unit 5. The pulse generator 4 generates a pulse for notifying the controller 2 of the timing at which the phases of the high-frequency signals S1 and S2 should be controlled. The power detection unit 5 detects the high-frequency power output from the high-frequency output unit 3. The high-frequency power output from the high-frequency output unit 3 is supplied to a load such as a plasma processing apparatus via the power detection unit 5 and the matching unit 200. Matching box 200 matches impedance with a load.

The high frequency generator 1 includes, for example, a direct digital synthesizer. Voltage of high frequency signal S1 generated by high frequency generator 1And (4) showing. Voltage of high frequency signal S2 generated by high frequency generator 1And (4) showing. A is for example a fixed amplitude. f is a Frequency set by the control unit 2, and is, for example, a Frequency of an industrial RF band (Radio Frequency) such as 2MHz, 13.56MHz, 27MHz, or 60 MHz.(or) Is the phase difference between the high frequency signal S1 and the high frequency signal S2.(or) Is adjusted to the phase difference θ set by the control unit 2. The control unit 2 sets the phase in the high frequency generating unit 1Andin the case of (3), the high-frequency generation unit 1 may adjust so that the phase difference between the high-frequency signal S1 and the high-frequency signal S2 satisfies(or) And (4) finishing.

The control Unit 2 includes a CPU (Central Processing Unit), not shown. The control unit 2 controls the operation of each unit in accordance with a control program stored in advance in a ROM (Read Only Memory), and performs processing such as input/output and calculation. The temporarily generated information is stored in a RAM (Random Access Memory). For example, a computer program for specifying the order of each process performed by the CPU is loaded into the RAM by a means not shown, and the loaded computer program is executed by the CPU. The control unit 2 may include a microcomputer or a dedicated hardware circuit.

The high-frequency output unit 3 includes DC-RF conversion units 31 and 32 and a power combining unit 33. The DC-RF converter 31 generates a high-frequency voltage V1 having a phase corresponding to the high-frequency signal S1 generated by the high-frequency generator 1. The DC-RF converter 32 generates a high-frequency voltage V2 having a phase corresponding to the high-frequency signal S2 generated by the high-frequency generator 1. The high-frequency voltages V1 and V2 correspond to the 1 st high-frequency voltage and the 2 nd high-frequency voltage, respectively. The power combining unit 33 combines the high-frequency power P1 based on the high-frequency voltage V1 generated by the DC-RF converter 31 and the high-frequency power P2 based on the high-frequency voltage V2 generated by the DC-RF converter 32. DC power is supplied from the DC power supply 30 to the DC-RF converters 31 and 32. The high-frequency component of the high-frequency power Ps synthesized by the power synthesis unit 33 is removed by the filter circuit 34. After the high-frequency component is removed, the fundamental component of the high-frequency power Ps is output to the load side.

The DC-RF conversion units 31 and 32 each include, for example, a half-bridge type D-class amplifier, a capacitor, and an LC low-pass filter. The capacitor cuts off the direct current contained in the output of the class D amplifier. The LC low pass filter removes harmonics contained in the output of the class D amplifier. The high-frequency voltage V1 generated by the DC-RF conversion unit 31 is represented by V (t) -Bsin (2 pi ft + θ 1). The high-frequency voltage V2 generated by the DC-RF conversion unit 32 is represented by V (t) -Bsin (2 pi ft + θ 2). B is a fixed amplitude corresponding to the voltage of the dc power supply 30. The phase difference θ 2- θ 1 (or θ 1- θ 2) between the high-frequency voltage V1 and the high-frequency voltage V2 is equal to the phase difference θ between the high-frequency signal S1 and the high-frequency signal S2.

As described above, the high-frequency power P1 is based on the 1 st high-frequency voltage V1 generated by the DC-RF converter 31. The high-frequency power P2 is based on the 2 nd high-frequency voltage V2 generated by the DC-RF converter 32. The power combining unit 33 combines the high-frequency powers P1 and P2 in accordance with the phase difference between the high-frequency voltage V1 and the high-frequency voltage V2, that is, the phase difference between the high-frequency signal S1 and the high-frequency signal S2. Thus, the power combining unit 33 adjusts the magnitude of the output high frequency power Ps. The power combining unit 33 will be described below.

Fig. 2 is a circuit diagram showing a configuration example of the power combining unit 33. The power combining section 33 includes a hybrid circuit including a resistor R and a transmission transformer Tt. With respect to the transmission transformer Tt, the ratio of the number of turns of the 1 st winding to the number of turns of the 2 nd winding is 1 to 1. The power combining section 33 also has 2 input ports N1 and N2 and 1 summing port Ns. A high-frequency voltage V1 is applied to the input port N1. A high-frequency voltage V2 is applied to the input port N2.

One end of the input port N1 is connected to one end of the resistor R and one end of the 1 st winding of the transmission transformer Tt as a winding start point. The other end of the 1 st winding of the transmission transformer Tt is connected to one end of the 2 nd winding as a winding start point and one end of the summing port Ns. The other end of the 2 nd winding of the transmission transformer Tt is connected to the other end of the resistor R and one end of the input port N2. The input ports N1 and N2 and the summing port Ns are connected to the ground potential at the respective other ends thereof.

A load is connected at the summing port Ns. It is known that when the impedance of the load is R0/2, the input impedance of each of the input ports N1 and N2 becomes R0 by setting the resistance value of the resistor R to 2R 0. Which is described in detail in Japanese patent laid-open publication No. 2017-201630. High-frequency power P1 is input from the input port N1. High-frequency power P2 is input from the input port N2. The high-frequency power P1 is expressed by the following formula (1) using the above-described voltage formula representing the high-frequency voltage V1. The high-frequency power P2 is expressed by the following expression (2) using the above-described voltage expression representing the high-frequency voltage V2.

P1＝B²sin²(2πft+θ1)/R0··············(1)

P2＝B²sin²(2πft+θ2)/R0··············(2)

According to Japanese patent laid-open publication No. 2017-201630, the currents flowing through the input ports N1 and N2 and the current flowing through the resistor R are calculated by using the above-described voltage formulas representing the high-frequency voltages V1 and V2, respectively. Then, the currents flowing through the 1 st winding and the 2 nd winding of the transmission transformer Tt are calculated, and the current output from the summing port Ns is calculated. As a result, the high-frequency voltage Vs and the high-frequency power Ps output from the summing port Ns are expressed by the following expressions (3) and (4), respectively. Therefore, the average value Ps _ avr of the high-frequency power Ps is expressed by the following equation (5).

Vs＝Bcos(θ/2)·sin(2πft+θ/2)·········(3)

Ps＝Vs²/(R0/2)

＝2B²cos²(θ/2)·sin²(2πft+θ/2)/R0··(4)

Ps_avr＝B²cos²(θ/2)/R0··············(5)

Wherein θ: theta 2-theta 1

By comparing expressions (1), (2), and (4), the ratio η of the high-frequency power Ps output from the power combining unit 33 to the high-frequency power (P1+ P2) input to the power combining unit 33 is expressed by expression (6) below. The remaining high frequency power is dissipated in resistor R. When the ratio η at which the high-frequency powers P1 and P2 are combined is determined, the phase difference θ is obtained by the following equation (7).

η＝cos²(θ/2)························(6)

Even when the impedance of the load connected to the summing port Ns is different from Ro/2, the magnitude of the high-frequency power Ps output from the power combining unit 33 can be adjusted by changing the phase difference θ within the range of 0 to 2 pi. The configuration of the power combining unit 33 is not limited to the configuration shown in fig. 2. The power combining unit 33 may be configured to combine the high-frequency powers P1 and P2 using a so-called 90 ° hybrid circuit, for example. The power loss generated in the filter circuit 34 is not seen below. In this case, the high-frequency power Ps output from the power combining unit 33 is output from the high-frequency output unit 3 while maintaining the magnitude thereof.

The pulse generating unit 4 shown in fig. 1 includes, for example, a general-purpose timer IC or a timer built in a microcomputer. The pulse generator 4 generates a pulse having a cycle and a duty ratio set by the controller 2. The value of the wave height of the pulse is the so-called logic level. The period of the pulse is sufficiently long compared to the period expressed in the reciprocal of the frequency f. The frequency f is set by the control unit 2 in the high frequency generating unit 1. The pulse generator 4 sends the generated pulse to the controller 2, and periodically notifies the controller 2 of the start time point of the effective period of the pulse and the start time point of the ineffective period of the pulse.

For convenience, even when the duty ratio is set to 100%, the pulse generating unit 4 notifies the control unit 2 of 2 start time points. Hereinafter, the effective period and the ineffective period of the pulse generated by the pulse generating unit 4 will be referred to as a 1 st period and a 2 nd period, respectively. The repetition period of the 1 st period and the 2 nd period is referred to as a control period.

The power detection unit 5 includes a directional coupler, and detects forward power output to the load side by the high-frequency output unit 3 and reflected power reflected from the load side. The power detector 5 feeds back the detection result to the controller 2. The power detection unit 5 may be configured to detect only the traveling wave power.

The matching box 200 is required to match the impedance of the high-frequency output unit 3 and the load independently from the high-frequency power supply device 100. However, in the configuration in which the magnitude of the high-frequency power Ps output from the high-frequency output unit 3 changes in a relatively short cycle, it may be difficult to always match the impedance. Therefore, in embodiment 1, matching unit 200 focuses on impedance matching in period 1 described above. For this purpose, matching unit 200 is notified of the timing of period 1 from control unit 2. The signal indicating the 1 st period may be directly supplied from the pulse generator 4 to the matching unit 200.

In the above configuration, the control unit 2 can periodically change the magnitude of the high-frequency power Ps supplied to the load to the 1 st level and the 2 nd level in each of the 1 st period and the 2 nd period. The control unit 2 sets the pulse period and the duty ratio in the pulse generating unit 4 so as to be notified of the start time points of the 1 st period and the 2 nd period, respectively. The duty ratio is a ratio of the 1 st period to a control period that is a repetition period of the 1 st period and the 2 nd period. Thus, the pulse generating unit 4 periodically notifies the control unit 2 of the start time point of the 1 st period and the start time point of the 2 nd period by, for example, performing an interrupt.

When the start time points of the 1 st period and the 2 nd period are notified from the pulse generating unit 4, the control unit 2 sets different phase differences in the high-frequency generating unit 1 so that the high-frequency power Ps output from the power combining unit 33 has the 1 st level and the 2 nd level. Here, the phase difference corresponding to the 1 st level of the high-frequency power Ps and the phase difference corresponding to the 2 nd level of the high-frequency power Ps may be calculated in advance based on equations (5) and (7). In thatIn this case, the 2 calculated values are stored in a storage unit, not shown. The phase difference corresponding to each of the 1 st level and the 2 nd level may be calculated for each setting. The maximum value of the average value Ps _ avr of the high-frequency power Ps expressed by the formula (5) is (B)²/R0). When the phase difference is calculated every time setting is performed, the 1 st level is calculated relative to the maximum value (B)²R0) and the 2 nd level with respect to the maximum (B)²/R0). The phase difference θ for the calculated 2 η is individually calculated based on the equation (7). The maximum value of the average value Ps _ avr of the high-frequency power Ps may be calculated by actual measurement.

When the control unit 2 sets the phase difference θ in the high frequency generating unit 1, the high frequency powers P1 and P2 output from the DC-RF converters 31 and 32, respectively, are combined at the power combining unit 33 at a ratio η corresponding to θ. The synthesized high-frequency power Ps is supplied to the load. The high-frequency power Ps supplied to the load is adjusted to the 1 st level and the 2 nd level in the 1 st period and the 2 nd period, respectively. However, the actual magnitudes of the high-frequency powers P1 and P2 are affected by the fluctuation of the load impedance (R0/2) as shown in the above-described equations (1) and (2). The input impedance of the power combining unit 33 and the output impedances of the DC-RF converting units 31 and 32 are not necessarily matched. Further, the output impedance of the power combining unit 33 and the impedance of the load are not necessarily matched with each other. As a result, the ratio η of the combination in the power combining unit 33 also has a value different from the value calculated by the equation (6).

For this reason, the feedback control may be performed so that the high-frequency power Ps supplied from the high-frequency output unit 3 to the load approaches the target 1 st and 2 nd levels in each of the 1 st and 2 nd periods. Specifically, the control unit 2 individually calculates the deviation between the detection result of the forward power (or the difference between the forward power and the reflected power) fed back from the power detection unit 5 and the target 1 st level and 2 nd level in each of the 1 st period and the 2 nd period. The control unit 2 performs control to increase or decrease the phase difference θ set in the high-frequency generating unit 1 so that the calculated deviation approaches zero. Since there are various known methods for the specific feedback control, the description of the feedback control is omitted.

In the feedback control described above, in the configuration in which the detection result of forward power is fed back from the power detection unit 5, the phase difference θ is controlled so that the power consumed by the load is smaller than the target 1 st level and 2 nd level by the amount of reflected power. In the configuration in which the detection result of the difference between the forward power and the reflected power is fed back from the power detection unit 5, the phase difference θ is controlled so that the power actually consumed by the load becomes the target 1 st level and the target 2 nd level. In a configuration in which the response of the feedback control is relatively slow, for example, the phase difference θ may be controlled so that the average value of the detection results fed back from the power detection unit 5 becomes the average value of the target 1 st level and 2 nd level. In this case, the phase difference θ set by the control unit 2 in each of the 1 st period and the 2 nd period may be determined collectively for 1 or more control cycles.

As described above, the high-frequency power Ps is supplied from the high-frequency output unit 3 to the load. When the magnitude of the high frequency power Ps changes sharply from the 1 st level to a level greatly different from the 1 st level, or when the magnitude of the high frequency power Ps changes sharply from the 2 nd level to a level greatly different from the 2 nd level, there is a possibility that the plasma becomes unstable. Even when the duty ratio in the 1 st period is changed abruptly, the plasma may become unstable. For this reason, in embodiment 1, when the duty ratio in the 1 st period is changed, the duty ratio is decreased (or increased) and the 1 st level is increased (or decreased). Thereby, the temporal change of the duty ratio and the temporal change of the 1 st level in the 1 st period become smooth, and the average value of the high-frequency power Ps supplied from the high-frequency output unit 3 to the load is maintained constant. As a result, the plasma remains stable.

Fig. 3 is an explanatory diagram schematically showing the high-frequency power Ps in the case where the 1 st period is gradually decreased in the high-frequency power supply device 100 according to embodiment 1. The horizontal axes of the 2 graphs shown in fig. 3 are the same time axis (t). The upper diagram illustrates a case where the control cycle including the 1 st period and the 2 nd period starts from the 1 st period. The lower graph illustrates the case where the control cycle starts from period 2. The control period is denoted by T. The control unit 2 gradually decreases the duty ratio in the 1 st period in the order of 75%, 50%, and 25% in each control cycle, and increases the 1 st level in the order of 1167W, 1500W, and 2500W.

The 1 st period shown in the upper diagram and the 2 nd period shown in the lower diagram correspond to the effective period of the pulse generated by the pulse generator 4. The control unit 2, for example, gradually decreases the duty ratio set in the pulse generating unit 4. This makes the 1 st period of the upper graph gradually decrease in synchronization with the timing notified from the pulse generator 4. The step width when the duty ratio is gradually decreased is not limited to 25%, and may be a finer value. Alternatively, the same duty ratio may be reduced to a smaller duty ratio after being maintained for a plurality of cycles. The duty cycle may also be reduced linearly. In embodiment 1, the 2 nd level is fixed at 600W.

The average values of the high-frequency power Ps in each of the 1 st control period, the 2 nd control period, and the 3 rd control period shown in the upper diagram are denoted as Ps1, Ps2, and Ps 3. The average values Ps1, Ps2, and Ps3 are expressed by the following formulas (8), (9), and (10), respectively. The unit is W. The decimal point is rounded off below. The value of "100" subtracted in each equation is an assumed value of the reflected power in the 2 nd period. It is assumed in period 1 that impedance matching is achieved.

Ps1＝1167×0.75+(600-100)×0.25＝1000··(8)

Ps2＝1500×0.50+(600-100)×0.50＝1000··(9)

Ps3＝2500×0.25+(600-100)×0.75＝1000··(10)

In comparison with the upper diagram, in the lower diagram, there is only a difference that each control cycle starts from the 2 nd period. In the lower graph, the average value of the high-frequency power Ps in each control period is the same as that in the upper graph. In fig. 3, the temporal change of the high-frequency power Ps when the duty ratio is gradually decreased in the 1 st period is described. However, the temporal change in the high-frequency power Ps when the duty ratio is increased in the 1 st period is shown in fig. 3 with the orientation of the time axis reversed. In this case, the 1 st level is gradually decreased with an increase in the duty ratio in the 1 st period.

Fig. 4 is a graph showing a correspondence relationship between a duty ratio and a phase difference used in the high-frequency power supply device 100 according to embodiment 1. The contents of the table are stored in a storage unit, not shown, as a table. In the table, the power (W), the phase difference, and the amplitude (relative value) corresponding to a plurality of duty ratios are stored for the 1 st level and the 2 nd level, respectively. In fig. 3, 100%, 75%, 50%, and 25% can be given as the plurality of duty ratios, and the power (W), phase difference, and amplitude (relative value) corresponding to these are shown. The power at each of level 1 and level 2 corresponds to the power shown in fig. 3. The pulse level shown in fig. 4 indicates a relative value of the level of the pulse-like voltage signal corresponding to the magnitude of the power, and is used in embodiments 2 and 3 described later.

For example, the maximum value of the high-frequency power Ps synthesized by the power synthesis unit 33 is 2500W. In this case, the phase difference θ 14 is zero. The phase difference θ 13 is calculated based on the formula (6) and satisfies 1500/2500 ═ cos²Theta of (theta/2). Similarly, the phase difference θ 12 satisfies 1167/2500 ═ cos²Theta of (theta/2). The phase difference theta 11 satisfies 1000/2500 ═ cos²Theta of (theta/2). The phase differences theta 22 to theta 24 satisfy 600/2500 ═ cos²Theta of (theta/2). When the duty ratio is 100%, both the 1 st level and the 2 nd level (2 levels) are not present. For convenience, however, the 1 st level and the 2 nd level are 1000W to store the phase difference and the amplitude. A method of controlling the phase difference θ with reference to a table corresponding to the graph shown in fig. 4 is described below using a flowchart.

Fig. 5 is a flowchart showing a processing procedure of the control unit 2 for setting the duty ratio and the phase difference in the pulse generation unit 4 and the high frequency generation unit 1, respectively. Pa and Pt in the figure are pointers indicating the head addresses of the areas in which the contents of the respective columns of the graph shown in fig. 4 are stored, respectively. This pointer is hereinafter referred to as a column pointer. When the contents of each column are regarded as an array, Pa and Pt are pointers indicating the addresses of the array. Pa denotes the head address of the column currently being referred to. Pt denotes the head address of the column to be finally set as the target. Δ P is a difference indicating a distance between 2 column head addresses. The control unit 2 stores the pointer Pa of the current column and the pointer Pt of the target column.

When the duty ratio in the 1 st period is gradually decreased as shown in fig. 3, the control unit 2 sets the pointer of the column corresponding to 25% which is the final target duty ratio to Pt and sets the distance (positive value) between adjacent columns to Δ P. After that, the control section 2 starts the processing shown in fig. 5. The initial value of Pa is the pointer to the column corresponding to the duty cycle of 100%. When increasing the duty ratio in the 1 st period, the control unit 2 sets a value (negative value) obtained by inverting the sign of the distance between adjacent columns to Δ P when Pt is set as the pointer of the column corresponding to the target new duty ratio.

When the process of fig. 5 is started, the control unit 2 temporarily stores the pointer Pt of the column corresponding to the target duty ratio in the storage unit (not shown) (S11). Next, the control unit 2 adds Δ P to the pointer Pa of the current column (S12). Here, when Δ P is a positive value, the column indicated by Pa is changed to a column next to the stage where the duty ratio is smaller by 1. When Δ P is a negative value, the column indicated by Pa is changed to a column next to the stage where the duty ratio is larger by 1.

Thereafter, the controller 2 refers to the table corresponding to the graph shown in fig. 4 by the pointer Pa (S13), and reads the duty ratio from the content of the column indicated by Pa (S14). The control unit 2 sets the read duty ratio in the pulse generating unit 4 (S15). The duty ratio set here is reflected in the control period next to the current control period. The pulse generating unit 4 is set to a control cycle in the initialization process. Next, the control unit 2 reads out phase differences corresponding to the 1 st level and the 2 nd level from the content of the column denoted by Pa (S16).

After that, the control unit 2 determines whether or not the pulse generation unit 4 is notified of the rise in the 1 st period (S17). When the rise of the 1 st period is not notified (no in S17), the control unit 2 waits until the rise is notified. When notified of the rise of the 1 st period (yes in S17), the control unit 2 sets the phase difference corresponding to the 1 st level among the phase differences read out in advance in step S16 as the high frequency generation unit 1 (S18).

After that, the control unit 2 determines whether or not the pulse generation unit 4 is notified of the rise in the 2 nd period (S19). When the rise of the 2 nd period is not notified (no in S19), the control unit 2 waits until the rise of the 2 nd period is notified. When notified of the rise in the 2 nd period (yes in S19), the control unit 2 sets the phase difference corresponding to the 2 nd level among the phase differences read out in advance in step S16 as the high frequency generation unit 1 (S20).

After that, the control unit 2 determines whether or not the pointer Pa of the current column matches the pointer Pt of the target column (S21). When the pointer Pa and the pointer Pt match (yes in S21), the control unit 2 shifts the process to step S17 to periodically set phase differences corresponding to the 1 st level and the 2 nd level thereafter, respectively. When the pointer Pa does not coincide with the pointer Pt (no in S21), the control unit 2 determines whether or not the Pt used in step S21 has been changed (S22).

The fact that the pointer Pt is not changed indicates that the gradual decrease or gradual increase of the duty ratio in the 1 st period is not completed. If the pointer Pt has not been changed (no in S22), the control unit 2 advances the pointer Pa of the current column by 1, and proceeds the process to step S12. The pointer Pt is a pointer indicating that the target column is changed. When the pointer Pt is changed (yes in S22), the control unit 2 shifts the process to step S11 to start the sequence of gradual decrease or gradual increase of the duty ratio in the 1 st period from the beginning.

The processing procedure of the control unit 2 shown in fig. 5 corresponds to the case where the 1 st period starts earlier than the 2 nd period as shown in the upper stage of fig. 3. As shown in the lower stage of fig. 3, the processing procedure of the control unit 2 in the case where the 2 nd period starts earlier than the 1 st period may be partially changed from the table corresponding to the graph shown in fig. 4 and the processing procedure shown in fig. 5. Specifically, the duty ratio of each column initially stored in the table is changed from the duty ratio in the 1 st period to the duty ratio in the 2 nd period.

Thus, in step S15 of fig. 5, the pulse generator 4 sets the duty ratio of the 2 nd period, and therefore the start time of the 2 nd period is notified first in 1 control cycle. Therefore, the control section 2 may perform steps S17 to S20 as follows. In step S17 of fig. 5, the control unit 2 waits for the rise of the 2 nd period. In step S18, the control unit 2 sets a phase difference corresponding to the 2 nd level in the high frequency generating unit 1. In step S19, the control unit 2 waits for the rise in the 1 st period. In step S20, the control unit 2 sets a phase difference corresponding to the 1 st level in the high frequency generating unit 1.

According to embodiment 1, the control unit 2 periodically controls the phases of the high-frequency signals S1 and S2 generated by the high-frequency generation unit 1. The high-frequency output unit 3 outputs high-frequency power Ps based on the high-frequency signals S1 and S2 whose phases are controlled. The control unit 2 controls the phases of the high-frequency signals S1 and S2, so that the magnitude of the high-frequency power Ps output by the high-frequency output unit 3 is periodically adjusted to the 1 st level and the 2 nd level in each of the 1 st period and the 2 nd period. The 2 nd level is lower than the 1 st level. The control unit 2 further gradually decreases the duty ratio of the 1 st period with respect to the control period and increases the 1 st level while periodically controlling the phase. Thus, the average value of the high-frequency power Ps output from the high-frequency output unit 3 is kept constant. Therefore, the abrupt change of the high-frequency power Ps can be alleviated.

In addition, according to embodiment 1, the high-frequency generating unit 1 generates high-frequency signals S1 and S2 having the same frequency. The controller 2 individually controls the phase difference θ between the high-frequency signal S1 and the high-frequency signal S2 in each of the 1 st period and the 2 nd period. The DC-RF converters 31 and 32 are included in the high-frequency output unit 3. The DC-RF converter 31 generates a high-frequency voltage V1 having a phase corresponding to the high-frequency signal S1. The DC-RF converter 32 generates a high-frequency voltage V2 having a phase corresponding to the high-frequency signal S2. The high-frequency output unit 3 combines the high-frequency powers P1 and P2 based on the generated high-frequency voltages V1 and V2, respectively, at a ratio corresponding to the phase difference θ between the high-frequency voltage V1 and the high-frequency voltage V2. The high-frequency output unit 3 outputs the synthesized high-frequency power Ps. The high-frequency powers P1 and P2 are based on high-frequency voltages V1 and V2, respectively. In each of the 1 st period and the 2 nd period, the high-frequency powers P1 and P2 are combined at different ratios from each other. This enables the magnitude of the high-frequency power Ps output in each of the 1 st and 2 nd periods to be changed to the 1 st and 2 nd levels.

Further, according to embodiment 1, the control unit 2 controls the phase so that the magnitude of the high-frequency power Ps output from the high-frequency output unit 3 in the 1 st period coincides with the 1 st level, as detected by the power detection unit 5. Here, the 1 st level is a target value of the high-frequency power Ps to be output by the high-frequency output unit 3 in the 1 st period of the current control cycle. The control unit 2 controls the phase so that the magnitude of the high-frequency power Ps output from the high-frequency output unit 3 in the period 2 coincides with the level 2, as detected by the power detection unit 5. Here, the 2 nd level is a target value of the high-frequency power Ps to be output by the high-frequency output unit 3 in the 2 nd period of the current control cycle. As described above, since the control unit 2 controls the phase, the magnitude of the high-frequency power Ps output from the high-frequency output unit 3 in each control cycle can be accurately adjusted.

(modification 1)

Embodiment 1 is a mode in which the duty ratio in the 1 st period is gradually decreased (or increased) and the 1 st level is gradually increased (or decreased). Modification 1 is a mode in which both the duty ratio and the 2 nd level in the 1 st period are gradually decreased (or increased) and the 1 st level is gradually increased (or decreased). The block configuration of the high-frequency power supply device according to modification 1 is the same as the block configuration of the high-frequency power supply device 100 shown in fig. 1 of embodiment 1. Therefore, in modification 1, the same reference numerals are given to portions corresponding to embodiment 1, and the description of the structure thereof is omitted.

Fig. 6 is an explanatory diagram schematically showing the high-frequency power Ps when the duty ratio is gradually decreased in the 1 st period in the high-frequency power supply device 100 according to the modification 1. The horizontal axes of the 2 graphs shown in fig. 6 are the same time axis (t). The upper diagram illustrates a case where the control cycle including the 1 st period and the 2 nd period starts from the 1 st period. The lower graph illustrates a case where the control cycle is started from period 2. The duty ratio in the 1 st period is gradually decreased in the order of 75%, 50%, and 25% in each control period. In addition, the 1 st level was gradually increased in the order of 1056W, 1333W and 2500W, and the 2 nd level was gradually decreased in the order of 933W, 766W and 600W.

The average values of the high-frequency power Ps in each of the 1 st control period, the 2 nd control period, and the 3 rd control period shown in the upper diagram are denoted as Ps1, Ps2, and Ps 3. For example, the average values Ps1, Ps2, and Ps3 are expressed by the following formulae (11), (12), and (13), respectively. The unit is W. The decimal point is rounded off below.

Ps1＝1056×0.75+(933-100)×0.25＝1000··(11)

Ps2＝1333×0.50+(766-100)×0.50＝1000··(12)

Ps3＝2500×0.25+(600-100)×0.75＝1000··(13)

When compared with the upper diagram, in the lower diagram, there is only such a difference that each control cycle starts from the 2 nd period. In the lower graph, the average value of the high-frequency power Ps in each control period is the same as that in the upper graph. Fig. 6 illustrates a temporal change in the high-frequency power Ps when the duty ratio is gradually decreased in the 1 st period. The temporal change in the high-frequency power Ps when the duty ratio in the 1 st period is increased is shown by reversing the orientation of the time axis in fig. 6. In this case, the duty ratio in the 1 st period is increased. Along with this, level 1 was decreased and level 2 was increased.

Fig. 7 is a graph showing a correspondence relationship between a duty ratio and a phase difference used in the high-frequency power supply device 100 according to modification 1. The contents of the chart are stored as a table. In the table, power (W), phase difference, and amplitude (relative value) corresponding to a plurality of duty ratios are stored for the 1 st level and the 2 nd level, respectively. Fig. 7 shows the power (W), phase difference, and amplitude (relative value) corresponding to 100%, 75%, 50%, and 25% as examples of the plurality of duty ratios. The power at each of level 1 and level 2 corresponds to the power shown in fig. 6.

For example, the maximum value of the high-frequency power Ps synthesized by the power synthesis unit 33 is 2500W. In this case, the phase difference θ 34 is zero. The phase difference θ 33 is calculated based on the equation (6) and satisfies 1333/2500 ═ cos²Theta of (theta/2). Similarly, the phase difference θ 32 satisfies 1056/2500 ═ cos²Theta of (theta/2). The phase difference theta 31 satisfies 1000/2500 ═ cos²Theta of (theta/2). The phase difference theta 44 satisfies 600/2500 ═ cos²Theta of (theta/2). The phase difference theta 43 satisfies 766/2500 ═ cos²Theta of (theta/2). The phase difference theta 42 satisfies 933/2500 ═ cos²Theta of (theta/2).

The flowchart showing the processing procedure of the control unit 2 for periodically setting the phase difference in the high frequency generating unit 1 is the same as the flowchart shown in embodiment 1. Therefore, illustration and description of the flowchart in modification 1 are omitted.

As described above, according to modification 1, the controller 2 periodically controls the phases of the high-frequency signals S1 and S2 generated by the high-frequency generator 1. The control unit 2 gradually decreases the duty ratio of the 1 st period with respect to the control period during the control phase. Along with this, the control unit 2 gradually increases the 1 st level and gradually decreases the 2 nd level. Thus, the average value of the high-frequency power Ps output from the high-frequency output unit 3 is kept constant. Therefore, the abrupt change of the high-frequency power Ps can be alleviated.

(modification 2)

Embodiment 1 is a mode in which the duty ratio in the 1 st period is gradually decreased (or increased) and the 1 st level is gradually increased (or decreased). Modification 2 is a mode in which the 2 nd level is gradually decreased (or increased) and the 1 st level is gradually increased (or decreased). The block configuration of the high-frequency power supply device according to modification 2 is the same as the block configuration of the high-frequency power supply device 100 shown in fig. 1 of embodiment 1. Therefore, in modification 2, the same reference numerals are given to portions corresponding to embodiment 1, and the description of the structure thereof is omitted.

Fig. 8 is an explanatory diagram schematically showing the high-frequency power Ps in the high-frequency power supply device 100 according to modification 2 in which the 2 nd level is gradually decreased. The horizontal axes of the 2 graphs shown in fig. 8 are the same time axis (t). The upper diagram illustrates a case where the control cycle including the 1 st period and the 2 nd period starts from the 1 st period. The lower graph illustrates the case where the control cycle starts from period 2. In a state where the duty ratio in the 1 st period is fixed at 25%, the 1 st level is increased in the order of 1375W, 1750W, 2125W, and 2500W, and the 2 nd level is decreased in the order of 975W, 850W, 725W, and 600W.

The average values of the high-frequency power Ps in each of the 1 st control period, the 2 nd control period, and the 3 rd control period shown in the upper diagram are denoted as Ps1, Ps2, and Ps 3. For example, the average values Ps1, Ps2, and Ps3 are expressed by the following formulae (14), (15), and (16), respectively. The unit is W.

Ps1＝1375×0.25+(975-100)×0.75＝1000··(14)

Ps2＝1750×0.25+(850-100)×0.75＝1000··(15)

Ps3＝2500×0.25+(600-100)×0.75＝1000··(16)

When compared with the upper graph, in the lower graph, there is only such a difference that each control cycle is from the 2 nd period. In the lower graph, the average value of the high-frequency power Ps in each control period is the same as that in the upper graph. In fig. 8, the temporal change of the high-frequency power Ps when the 2 nd level is gradually decreased is described. The temporal change of the high-frequency power Ps when the level 2 is increased is shown in fig. 8 in which the direction of the time axis is reversed. In this case, the 1 st level is gradually decreased and the 2 nd level is gradually increased while the duty ratio in the 1 st period is fixed at a fixed value.

Fig. 9 is a graph showing a correspondence relationship between a duty ratio and a phase difference used in the high-frequency power supply device 100 according to modification 2. The contents of the chart are stored as a table. In the table, the power (W), the phase difference, and the amplitude (relative value) when the duty ratio is uniformly 25% are stored for the 1 st level and the 2 nd level, respectively. The power at each of level 1 and level 2 corresponds to the power shown in fig. 8.

For example, the maximum value of the high-frequency power Ps synthesized by the power synthesis unit 33 is assumed to be 2500W. In this case, the phase difference θ 55 is zero. The phase difference θ 54 is calculated based on the equation (6), and 2125/2500 ═ cos is satisfied²Theta of (theta/2). Similarly, the phase difference θ 53 satisfies 1750/2500 ═ cos²Theta of (theta/2). The phase difference theta 52 satisfies 1375/2500 ═ cos²Theta of (theta/2). The phase difference theta 51 satisfies 1000/2500 ═ cos²Theta of (theta/2). The phase difference theta 65 satisfies 600/2500 ═ cos²Theta of (theta/2), and the phase difference theta 64 satisfies 725/2500 ═ cos²Theta of (theta/2). The phase difference theta 63 satisfies 850/2500 ═ cos²(theta/2)Theta. The phase difference theta 62 satisfies 975/2500 ═ cos²Theta of (theta/2).

The flowchart showing the processing procedure of the control unit 2 for periodically setting the phase difference in the high frequency generating unit 1 is the same as the flowchart shown in embodiment 1. Therefore, illustration and description of the flowchart in modification 2 are omitted.

As described above, according to the modification 2, the control unit 2 periodically controls the phases of the high-frequency signals S1 and S2 generated by the high-frequency generation unit 1. While the control unit 2 controls the phase, the 1 st level is gradually increased and the 2 nd level is gradually decreased. Thus, the average value of the high-frequency power Ps output from the high-frequency output unit 3 is kept constant. Therefore, the abrupt change of the high-frequency power Ps can be alleviated.

(embodiment mode 2)

In embodiment 1, the control unit 2 periodically controls the phases of the high-frequency signals S1 and S2 generated by the high-frequency generation unit 1. The high-frequency output unit 3 outputs high-frequency power Ps based on the high-frequency signals S1 and S2 whose phases are controlled. The high-frequency power Ps output from the high-frequency output unit 3 is periodically adjusted to the 1 st level and the 2 nd level. In embodiment 2, the control unit 2 periodically controls the amplitude of the high-frequency signal generated by the high-frequency generation unit. The high-frequency output unit outputs high-frequency power based on the high-frequency signal whose amplitude is controlled. The magnitude of the high-frequency power output by the high-frequency output unit is periodically adjusted to the 1 st level and the 2 nd level.

Fig. 10 is a block diagram showing a configuration example of the high-frequency power supply device 100b according to embodiment 2. The high-frequency power supply device 100b includes a high-frequency generation unit 1b, a control unit 2b, and a high-frequency output unit 9. The high-frequency generator 1b generates a high-frequency signal Sm. The control unit 2b controls the amplitude of the high-frequency signal Sm generated by the high-frequency generation unit 1 b. The high-frequency output unit 9 outputs high-frequency power Po having a magnitude corresponding to the high-frequency signal Sm whose amplitude is controlled. The high-frequency power supply device 100b further includes a power detection unit 5 that detects the high-frequency power Po output from the high-frequency output unit 9. The high-frequency power Po output from the high-frequency output unit 9 is supplied to the load via the power detection unit 5 and the matching unit 200. The matching unit 200 matches impedance with the power detection unit 5 and the load. In embodiment 2, the same reference numerals are given to portions corresponding to those in embodiment 1, and the description of the structure thereof is omitted.

The high-frequency generator 1b includes a high-frequency oscillator 6, a pulse generator 7, and a multiplier 8. The high-frequency oscillator 6 oscillates a high-frequency continuous signal S0. The pulse generator 7 generates a pulse signal Vp having a rectangular waveform for modulating the continuous signal S0 oscillated by the high-frequency oscillator 6. The multiplier 8 multiplies the continuous signal S0 oscillated by the high-frequency oscillator 6 and the pulse signal Vp generated by the pulse generator 7, thereby modulating the amplitude of the continuous signal S0. A rectangular wave signal is a signal having a stepwise rise and fall. In a rectangular wave-shaped signal, the levels before and after rising are not necessarily zero levels. Here, the rectangular wave-shaped signal is also regarded as a generalized pulse signal. The rectangular wave signal is a period from rising to falling as an activation period.

The control unit 2b includes a CPU, a ROM, and a RAM, and is configured in the same manner as the control unit 2 shown in fig. 1 of embodiment 1 in terms of hardware. In terms of software, the control unit 2 periodically sets the duty ratio in the pulse generation unit 4, and periodically sets the phase difference θ in the high frequency generation unit 1. The control unit 2b periodically sets the duty ratio and the 2-pulse level in the pulse generating unit 7. Details thereof will be described later.

The high-frequency oscillator 6 includes, for example, a direct digital synthesizer. Voltage of high-frequency continuous signal S0 oscillated by high-frequency oscillator 6And (4) showing. The high-frequency oscillator 6 inputs the high-frequency continuous signal S0 to one of the multiplication inputs of the multiplier 8. A0 is a fixed amplitude.Is the initial phase. f is a frequency set by the control unit 2b, and is, for example, a frequency of an industrial RF band such as 2MHz, 13.56MHz, 27MHz, or 60 MHz.

The pulse generating unit 7 includes, for example, a direct digital synthesizer. The pulse generating unit 7 generates a pulse signal Vp having a high level and a low level in accordance with the period, the duty ratio, and 2 pulse levels set by the control unit 2 b. The pulse generator 7 inputs the generated pulse signal Vp to the other multiplication input of the multiplier 8. The period of the pulse signal Vp is sufficiently longer than the period indicated by the reciprocal of the frequency f set in the high-frequency oscillator 6 by the control unit 2 b. The pulse generator 7 periodically notifies the controller 2b of the start time point of the period in which the pulse signal Vp is at the high level and the start time point of the period in which the pulse signal Vp is at the low level.

For convenience, even when the pulse generating unit 7 sets the duty ratio to 100%, the control unit 2b is notified of 2 start time points. As described above, the pulse generator 7 generates the pulse signal Vp. Hereinafter, a period in which the pulse signal Vp is at a high level is referred to as a 1 st period. A period in which the pulse signal Vp is at a low level is referred to as a 2 nd period. The repetition period of the 1 st period and the 2 nd period is referred to as a control period.

The multiplier 8 includes, for example, an analog multiplier or a digital modulator. The multiplier 8 receives the instantaneous value of the high-frequency continuous signal S0 and the instantaneous value of the pulse signal Vp as the multiplication inputs of 2 numbers. The multiplier 8 multiplies the instantaneous value of the high-frequency continuous signal S0 by the instantaneous value of the pulse signal Vp. This performs amplitude offset modulation of the high-frequency continuous signal S0. The multiplier 8 outputs a high-frequency signal Sm obtained by amplitude offset modulation. When the signal level of the pulse signal Vp is the fixed reference level Lr and the duty ratio is 100%, the high-frequency signal Sm output by the multiplier 8 is expressed by the following expression (17) using a voltage expression representing the above-described continuous signal S0.

Wherein B0: fixed amplitude of vibration

The high frequency output section 9 includes a linear amplifier. The high-frequency output unit 9 linearly amplifies the high-frequency signal Sm input from the high-frequency generator 1b, which is the multiplier 8, and outputs the high-frequency voltage Vo obtained by the amplification. Thereby, the high-frequency power Po having a magnitude corresponding to the high-frequency voltage Vo is supplied to the load side. The impedance of the load side viewed from the high-frequency output unit 9 is assumed to be R0/2 as in embodiment 1. When the signal level of the pulse signal Vp is the fixed reference level Lr, the high-frequency power Po output by the high-frequency output unit 9 is expressed by the following expression (18) using expression (17). In this case, the average value Po _ avr of the high-frequency power Po is expressed by the following expression (19) and is proportional to the square of the reference level Lr.

Po_avr＝(G·Lr·B0)²/R0···············(19)

Wherein, G: amplification factor of high frequency output unit 9

With the above configuration, the controller 2b can periodically change the magnitude of the high-frequency power Po supplied to the load to the 1 st level and the 2 nd level in each of the 1 st period and the 2 nd period. The control unit 2b sets the period and duty ratio of the pulse signal Vp in the pulse generating unit 7 so as to be notified of the start time points of the 1 st period and the 2 nd period, respectively. The duty ratio is a ratio of the 1 st period to a control period that is a repetition period of the 1 st period and the 2 nd period. Thus, the pulse generating unit 7 periodically notifies the control unit 2b of the start time point of the 1 st period and the start time point of the 2 nd period, for example, by performing an interrupt.

When the start time points of the 1 st period and the 2 nd period are notified from the pulse generator 7, the controller 2b sets different pulse levels in the pulse generator 7 so that the magnitudes of the high-frequency power Po output from the high-frequency output unit 9 become the 1 st level and the 2 nd level. The pulse level set by the pulse generator 7 at the start time point of each of the 1 st period and the 2 nd period is reflected on the signal level in the effective period and the ineffective period of the pulse signal Vp generated by the pulse generator 7. The high frequency power Po is then adjusted to the 1 st level and the 2 nd level based on these signal levels.

Here, the pulse level corresponding to the 1 st level and the pulse level corresponding to the 2 nd level may be calculated in advance based on equation (19). In this case, the 2 calculated values are stored in a storage unit, not shown. The pulse levels corresponding to the 1 st level and the 2 nd level may be calculated for each setting. As described above, the average value Po _ avr of the high-frequency power Po is expressed by equation (19). Specifically, the magnification of the 1 st level with respect to the average value Po _ avr and the magnification of the 2 nd level with respect to the average value Po _ avr are calculated. The high-level and low-level pulse levels are calculated by multiplying the square root of each of the calculated 2 magnifications by the above-mentioned reference level Lr. The average value Po _ avr of the high-frequency power Po when the signal level of the pulse signal Vp is the fixed reference level Lr may be calculated by actual measurement.

The feedback control can be performed so that the high-frequency power Po supplied from the high-frequency output unit 9 to the load in each of the 1 st period and the 2 nd period approaches the target 1 st level and the 2 nd level. This is the same as in embodiment 1. When the 1 st level or the 2 nd level is changed, the duty ratio in the 1 st period is gradually decreased (or increased) together with the change of the 1 st level or the 2 nd level, and the plasma is kept stable. This is also the same as in embodiment 1, modification 1 and modification 2.

For example, when the duty ratio in the 1 st period is decreased (or increased) and the 1 st level is increased (or decreased), the pulse level set in the pulse generator 7 is changed in accordance with the change in the duty ratio. For example, the graph shown in fig. 4 of embodiment 1 is used to change the pulse level. When the pulse level is changed as described above, the 1 st period corresponds to the effective period of the rectangular wave-shaped pulse signal Vp generated by the pulse generator 7. The control unit 2, for example, gradually decreases the duty ratio set in the pulse generating unit 7. This makes it possible to gradually decrease the 1 st period in synchronization with the timing notified from the pulse generator 7.

Similarly, when both the duty ratio and the 2 nd level in the 1 st period are decreased (or increased) and the 1 st level is increased (or decreased), the pulse level set in the pulse generating unit 7 is changed in accordance with the change in the duty ratio. For example, a graph shown in fig. 7 of modification 1 is used to change the pulse level. In addition, it is assumed that the 2 nd level is decreased (or increased) and the 1 st level is increased (or decreased). In this case, the pulse level set in the pulse generator 7 is decreased (or increased) toward the 2 nd level of the target, and the pulse level set in the pulse generator 7 is increased (or decreased) toward the 1 st level of the target. For example, a graph shown in fig. 9 of modification 2 is used to gradually decrease or increase the pulse level.

In fig. 4, 7, and 9, the pulse level at which the 1 st level is 1000W is set as the reference level Lr. The square root of the magnification of each of the 1 st level and the 2 nd level with respect to 1000W is set as a relative pulse level with respect to the reference level L. A method of controlling the pulse level with reference to tables corresponding to the graphs shown in fig. 4, 7, and 9 will be described below using a flowchart.

Fig. 11 is a flowchart showing a processing procedure of the control unit 2b for setting the duty ratio and the pulse level to the pulse generating unit 7. Steps S31 to S42 in the figure except for steps S36, S38, and S40 correspond to steps S11 to S22 shown in fig. 5 of embodiment 1. The processing contents are the same as those in embodiment 1. Therefore, the following description will focus on steps S36, S38, and S40.

When the process of fig. 11 is started and the processes of steps S31 to S35 are ended, the control unit 2b reads out the pulse levels corresponding to the 1 st level and the 2 nd level from the content of the column indicated by Pa (S36). After that, the control unit 2b determines whether or not the pulse generation unit 7 is notified of the rise in the 1 st period (S37). When the rise in the 1 st period is not notified (no in S37), the control unit 2b waits until the rise is notified. When notified of the rise of the 1 st period (yes in S37), the control unit 2b reads in advance the pulse potential pulse generating unit 7 corresponding to the 1 st level out of the pulse levels in step S36 (S38).

After that, the control unit 2b determines whether or not the pulse generation unit 7 is notified of the rise in the 2 nd period (S39). When the rise in period 2 is not notified (no in S39), the control unit 2b waits until the rise is notified. When notified of the rise of the 2 nd period (yes at S39), the control unit 2b sets the pulse level corresponding to the 2 nd level as the pulse generating unit 7 among the pulse levels read in advance at step S36 (S40). The following processing is the same as in embodiment 1.

As described above, according to embodiment 2, the control unit 2b periodically controls the amplitude of the high-frequency signal Sm generated by the high-frequency generation unit 1 b. The high-frequency output unit 9 outputs the high-frequency power Po based on the high-frequency signal Sm whose amplitude is controlled. The amplitude of the high-frequency signal Sm is periodically controlled by the controller 2b, and the high-frequency power Po output by the high-frequency output unit 9 is periodically adjusted to the 1 st level and the 2 nd level in each of the 1 st period and the 2 nd period. The 2 nd level is lower than the 1 st level. The control unit 2b further gradually decreases or increases at least one of the duty ratio of the 1 st period with respect to the control period and the 2 nd level, and gradually increases or decreases the 1 st level, while periodically controlling the amplitude. Thereby, the average value of the high-frequency power Po output from the high-frequency output unit 9 is kept constant. Therefore, the abrupt change of the high-frequency power Po can be alleviated.

In embodiment 2, the controller 2b controls the amplitude of the high-frequency signal Sm generated by the high-frequency generator 1b in each of the 1 st period and the 2 nd period. The high-frequency output unit 9 generates high-frequency power Po having a magnitude corresponding to the amplitude-controlled high-frequency signal Sm. Therefore, the magnitudes of the high-frequency power Po output in each of the 1 st period and the 2 nd period can be changed to the 1 st level and the 2 nd level.

(embodiment mode 3)

In embodiment 2, the 1 high-frequency output unit 9 supplies the high-frequency power Po adjusted to the 1 st level and the 2 nd level by amplitude offset modulation to the load. In embodiment 3, one high-frequency output section 9 supplies the high-frequency power Po1 of the 1 st level to the load only during the 1 st period. Further, the other high-frequency output unit 9 supplies the high-frequency power Po2 of the 2 nd level to the load only during the 2 nd period. One high-frequency output unit 9 corresponds to the 1 st high-frequency output unit. The other high-frequency output unit corresponds to the 2 nd high-frequency output unit.

Fig. 12 is a block diagram showing a configuration example of a high-frequency power supply device 100c according to embodiment 3. The high-frequency power supply device 100c includes a high-frequency generation unit 1c, a control unit 2c, and high-frequency output units 9 and 9. The high-frequency generator 1c generates high-frequency signals Sm1 and Sm 2. The high-frequency signals Sm1 and Sm2 correspond to the 1 st high-frequency signal and the 2 nd high-frequency signal, respectively. The controller 2c controls the amplitudes of the high-frequency signals Sm1 and Sm2 generated by the high-frequency generator 1 c. One high-frequency output unit 9 outputs high-frequency power Po1 having a magnitude corresponding to the amplitude-controlled high-frequency signal Sm 1. The other high-frequency output unit 9 outputs high-frequency power Po2 having a magnitude corresponding to the high-frequency signal Sm2 whose amplitude is controlled.

The high-frequency power supply device 100c further includes power detection units 5 and 5 that detect the high-frequency powers Po1 and Po2 output from the high-frequency output units 9 and 9, respectively. The high-frequency power Po1 output from one high-frequency output unit 9 is supplied to the electrode 301 of the load 300 via one power detection unit 5 and one matching unit 200. The high-frequency power Po2 output from the other high-frequency output unit 9 is supplied to the electrode 301 of the load 300 via the other power detection unit 5 and the other matching unit 200. Matching boxes 200 and 200 match impedance with load 300. The load 300 is a plasma processing apparatus. The other electrode 302 of the load 300 is grounded. The same reference numerals are given to portions corresponding to embodiments 1 and 2, and the description of the structures is omitted.

The high-frequency generator 1c includes a high-frequency oscillator 6, a pulse generator 7b, and multipliers 8 and 8. The high-frequency oscillator 6 oscillates a high-frequency continuous signal S0. The pulse generator 7b generates pulse signals Vp1 and Vp2 for modulating the continuous signal S0 oscillated by the high-frequency oscillator 6. One multiplier 8 multiplies the continuous signal S0 oscillated by the high-frequency oscillator 6 by the pulse signal Vp1 generated by the pulse generator 7b to modulate the amplitude of the continuous signal S0. The other multiplier 8 multiplies the continuous signal S0 oscillated by the high-frequency oscillator 6 by the pulse signal Vp2 generated by the pulse generator 7b to modulate the amplitude of the continuous signal S0.

The control unit 2c includes a CPU, a ROM, and a RAM, and is configured in the same manner as the control unit 2b shown in fig. 10 of embodiment 2. The detection results of the power detection units 5 and 5 are individually input to the control unit 2 c. Further, the controller 2c notifies the matchers 200 and 200 of the timings associated with the 1 st period and the 2 nd period, respectively. The pulse generator 7b may directly apply the signal indicating the 1 st period and the signal indicating the 2 nd period to the matching units 200 and 200, respectively.

The high-frequency oscillator 6 distributes the oscillating continuous signal S0 to the multipliers 8 and 8. Thus, the continuous signal S0 is input to one of the multiplication inputs of the multipliers 8 and 8. Further, 2 continuous signals having different frequencies may be input to the multipliers 8 and 8, respectively.

The pulse generator 7b generates a high-level pulse signal Vp1 in accordance with the cycle and duty ratio set by the controller 2c, and inputs the generated pulse signal Vp1 to the other multiplier input of the multiplier 8. The pulse generator 7b further generates a pulse signal Vp2 having a lower level than the pulse signal Vp1 during the period of failure of the pulse signal Vp1, and inputs the generated pulse signal Vp2 to the other multiplication input of the other multiplier 8. In other words, the pulse generator 7b outputs the pulse signal Vp1 in the 1 st period and the pulse signal Vp2 in the 2 nd period, as the pulse signal Vp having a rectangular wave shape generated by the pulse generator 7 of embodiment 2. The pulse signals Vp1 and Vp2 are pulse signals in a narrow sense of zero level during the failure. The pulse generator 7b periodically notifies the controller 2c of the start time points of the generated pulse signals Vp1 and Vp 2.

For convenience, even when the duty ratio is set to 100% in the pulse generating unit 7b, the control unit 2c is notified of 2 start time points. As described above, the pulse generator 7b generates the pulse signals Vp1 and Vp 2. The period during which the pulse signal Vp1 is asserted is hereinafter referred to as the 1 st period. The period during which the pulse signal Vp2 is asserted is referred to as the 2 nd period. The repetition period of the 1 st period and the 2 nd period is referred to as a control period.

The multipliers 8 and 8 perform amplitude offset modulation of the high-frequency continuous signal S0, respectively. One multiplier operator 8 outputs a high frequency signal Sm 1. The other multiplier 8 outputs a high-frequency signal Sm 2. The high-frequency output units 9 and 9 linearly amplify the high-frequency signals Sm1 and Sm2 output from the multipliers 8 and 8, i.e., the high-frequency generator 1c, respectively. The high-frequency output units 9 and 9 output the amplified high-frequency voltages Vo1 and Vo2, respectively. Thereby, high-frequency powers Po1 and Po2 having magnitudes corresponding to the high-frequency voltages Vo1 and Vo2, respectively, are supplied to the load 300.

With the above configuration, the controller 2c can adjust the magnitude of the high-frequency power Po1 supplied to the load 300 to the 1 st level in the 1 st period. The controller 2c can adjust the magnitude of the high-frequency power Po2 supplied to the load 300 to the 2 nd level in the 2 nd period. The control unit 2c sets the pulse period and the duty ratio of the pulse signal Vp1 in the pulse generation unit 7b so as to be notified of the start time points of the 1 st period and the 2 nd period, respectively. The duty ratio is a ratio of the 1 st period to a control period that is a repetition period of the 1 st period and the 2 nd period. Thus, the pulse generator 7b periodically notifies the controller 2c of the start time point of the 1 st period and the start time point of the 2 nd period by, for example, interrupting the pulse generator.

When the start time point of the 1 st period is notified from the pulse generator 7b, the controller 2c sets one pulse level in the pulse generator 7b so that the magnitude of the high-frequency power Po1 output from one high-frequency output unit 9 becomes the 1 st level. When the pulse generator 7b is notified of the start time point of the 2 nd period, the controller 2c sets the other pulse level in the pulse generator 7b so that the high-frequency power Po2 output from the other high-frequency output unit 9 has the 2 nd level. The control section 2c sets the pulse level. The pulse level corresponding to the 1 st level and the pulse level corresponding to the 2 nd level can be calculated in advance in the same manner as in embodiment 2. In this case, the 2 calculated values are stored in a storage unit, not shown. The pulse levels corresponding to the 1 st level and the 2 nd level can be calculated for each setting.

As described above, in each of the 1 st period and the 2 nd period, the high-frequency power Po1 and Po2 are supplied from the high-frequency output units 9 and 9 to the load 300. The feedback control can be performed so that the high-frequency powers Po1 and Po2 are close to the target 1 st and 2 nd levels, respectively. This is the same as in embodiments 1 and 2. When the 1 st level or the 2 nd level is changed, the duty ratio in the 1 st period is gradually decreased (or increased) together with the change of the 1 st level or the 2 nd level, and the plasma is kept stable. This is also the same as in embodiments 1 and 2 and modifications 1 and 2.

As described above, the contents set by the control unit 2c to the pulse generating unit 7b are the same as those set by the control unit 2b to the pulse generating unit 7 according to embodiment 2. For this reason, the processing procedure of the control unit 2c for periodically setting the duty ratio and the pulse level to the pulse generating unit 7b is the same as the processing procedure shown in fig. 11 of embodiment 2. Therefore, the illustration and description of the flowcharts showing the processing order are omitted here.

As described above, according to embodiment 3, the controller 2c periodically controls the amplitudes of the high-frequency signals Sm1 and Sm2 generated by the high-frequency generator 1 c. The high-frequency output units 9 and 9 output high-frequency powers Po1 and Po2 based on the high-frequency signals Sm1 and Sm2, respectively, whose amplitudes are controlled. The amplitude of the high-frequency signals Sm1 and Sm2 is periodically controlled by the controller 2c, and the magnitudes of the high-frequency powers Po1 and Po2 are periodically adjusted to the 1 st level and the 2 nd level in the 1 st period and the 2 nd period, respectively. The control unit 2c further gradually decreases or increases at least one of the duty ratio of the 1 st period with respect to the control period and the 2 nd level, and gradually increases or decreases the 1 st level, during the period in which the amplitude is periodically controlled. Thus, the average value of the sum of the high-frequency powers Po1 and Po2 output from the high-frequency output units 9 and 9, respectively, is kept constant. That is, when at least one of the duty ratio and the 2 nd level in the 1 st period is decreased, the 1 st level is increased. When at least one of the duty ratio and the 2 nd level in the 1 st period is increased, the 1 st level is decreased gradually. Thus, the average value of the sum of the high-frequency power Po1 and Po2 is kept constant. Therefore, the abrupt change of the high-frequency power Po can be alleviated.

In embodiment 3, the controller 2c adjusts the magnitudes of the high-frequency power Po1 and Po2 supplied to the load 300 to the 1 st level and the 2 nd level by controlling the amplitude of each of the high-frequency signals Sm1 and Sm2 in the same manner as in embodiment 2. However, the configuration of adjusting the respective magnitudes of the 2 nd system high-frequency power supplied to the load 300 to the 1 st level and the 2 nd level is not limited to the above configuration. Assume that 2 signals are included in a set of high frequency signals. For example, 2 sets of high-frequency signals may be generated instead of the high-frequency signals Sm1 and Sm 2. In this configuration, for example, the control unit controls the phase difference for each group of high-frequency signals, as in the case of embodiment 1. Thus, the magnitudes of the 2 nd high-frequency power supplied to the load 300 are adjusted to the 1 st level and the 2 nd level, respectively.

The embodiments disclosed herein are illustrative in all respects and should not be considered as being limiting. The scope of the present invention is defined not by the above description but by the claims, and is intended to include all modifications within the scope and meaning equivalent to the claims. In addition, the technical features described in the respective embodiments can be combined with each other.