阅读说明：本技术 高频电源 (High frequency power supply ) 是由 笠井善信 于 2015-12-09 设计创作，主要内容包括：本发明提供一种高频电源,能够使高频电力作为高速地变化的期望的波形输出。所述高频电源1包括合成2个DC-RF转换部4A、4B和两DC-RF转换部4A、4B的输出的RF合成部5。DC-RF转换部4A、4B分别将从高频信号生成部8输入的高频电压v-a、v-b放大输出高频电压v-(PA)、v-(PB)。RF合成部5以与高频电压v-(PA)、v-(PB)的相位差θ对应的合成比例输出高频电压v-(PX)。控制部9将相位差θ在θ1与θ2之间切换。由此,从RF合成部5输出的输出电力P-X成为具有高电平期间和低电平期间的脉冲状的高频电力。相位差θ的切换能够高速地进行,因此能够输出提高了第一电平与第二电平的切换的频率的脉冲状的高频电力。(The invention provides a high-frequency power supply, which can output high-frequency power as a desired waveform which changes at a high speed. The high-frequency power supply 1 includes an RF combining unit 5 that combines outputs of 2 DC-RF conversion units 4A and 4B and two DC-RF conversion units 4A and 4B. The DC-RF converters 4A and 4B respectively convert the high-frequency voltage v input from the high-frequency signal generator 8 a 、v b Amplifying the output high frequency voltage v PA 、v PB . An RF combining part 5 for combining with the high frequency voltage v PA 、v PB The synthesized ratio corresponding to the phase difference theta of (a) outputs the high-frequency voltage v PX . The control section 9 switches the phase difference θ between θ 1 and θ 2. Thereby, the output power P outputted from the RF combining section 5 X Has a high level period and a low level periodThe pulse-like high-frequency power of (1). Since the phase difference θ can be switched at high speed, it is possible to output pulsed high-frequency power with an increased frequency of switching between the first level and the second level.)

1. A high frequency power supply, comprising:

a plurality of high-frequency signal generating units for outputting high-frequency signals whose phase difference can be changed;

a high-frequency generation unit including a plurality of DC-RF conversion sections that amplify the high-frequency signals generated by the high-frequency signal generation unit with a direct-current voltage and output the amplified high-frequency signals as high-frequency voltages whose phase differences can be changed;

a voltage supply unit for supplying a DC voltage to each of the DC-RF converters constituting the plurality of DC-RF converters;

a high-frequency synthesizing unit that synthesizes a plurality of high frequencies output from the plurality of DC-RF converters in a predetermined ratio based on the phase difference and outputs the synthesized high frequencies to a load; and

and an output control unit that controls the high-frequency power output from the high-frequency combining unit by giving information including information on phase difference to each of the high-frequency signal generating units constituting the plurality of high-frequency signal generating units, and changing a phase difference between the high-frequency voltages output from the DC-RF converters corresponding to each of the high-frequency signal generating units

The voltage supply unit supplies a direct current voltage having a voltage value greater than 0 to each of the DC-RF conversion sections to maintain a state in which each of the DC-RF conversion sections constituting the plurality of DC-RF conversion sections generates a high frequency voltage,

the plurality of high frequency signal generating units output the high frequency signals to maintain a state in which the respective DC-RF converting parts generate high frequency voltages while the direct current voltage having the voltage value greater than 0 is supplied to the respective DC-RF converting parts, thereby outputting the high frequency voltages from the plurality of DC-RF converting parts,

the output control unit may perform (a) constant control in which a power value of the high-frequency power output by the high-frequency combining unit is constant without changing a phase difference between the plurality of DC-RF conversion units; (b) an increase control for changing a phase difference between the plurality of DC-RF converters to increase a power value of the high-frequency power output from the high-frequency combining unit; and (c) a reduction control for changing a phase difference between the plurality of DC-RF converters so as to reduce a power value of the high-frequency power output from the high-frequency synthesizing unit, wherein the control is arbitrarily combined so that the power value of the high-frequency power output from the high-frequency synthesizing unit becomes a desired power value of 0 or more,

each of the DC-RF converters constituting the plurality of DC-RF converters receives as input a high-frequency signal output from only one of the high-frequency signal generating units constituting the plurality of high-frequency signal generating units.

2. The high frequency power supply according to claim 1, wherein:

the output control unit switches the phase difference between a first prescribed value and a second prescribed value.

3. The high frequency power supply according to claim 2, wherein:

the predetermined ratio when the phase difference is the first predetermined value is larger than the predetermined ratio when the phase difference is the second predetermined value.

4. The high frequency power supply according to claim 3, wherein:

the first predetermined value is 0[ deg ] or more and less than 90[ deg ],

the second predetermined value is 90[ deg ] or more and 180[ deg ] or less.

5. The high frequency power supply according to claim 4, wherein:

the first prescribed value is 0[ deg ].

6. The high-frequency power supply according to claim 4 or 5, wherein:

the second prescribed value is 180[ deg ].

7. The high-frequency power supply according to any one of claims 2 to 4, wherein:

the output control means performs feedback control of the high-frequency power by changing the first predetermined value or the second predetermined value.

8. The high-frequency power supply according to any one of claims 2 to 5, wherein:

the high frequency generating unit generates a first high frequency and a second high frequency,

the output control unit switches the phase difference between the second high frequency and the first high frequency between the first predetermined value and the second predetermined value.

9. The high frequency power supply according to claim 1, wherein:

the output control unit switches the phase difference among a first prescribed value, a second prescribed value, and a third prescribed value.

10. The high frequency power supply according to claim 1, wherein:

the output control unit changes the phase difference according to a linear function.

11. The high frequency power supply according to claim 1, wherein:

the output control unit changes the phase difference according to the following equation,

where θ is the phase difference and x (t) is a function representing the desired waveform.

12. The high frequency power supply according to claim 1, wherein:

the output control unit switches the phase difference between a first predetermined value and a value of a predetermined function.

13. The high frequency power supply according to claim 2, wherein:

the output control means sets the phase difference to a phase difference that makes an output larger than an output when the phase difference is the first predetermined value and the second predetermined value when the output to the load is started.

14. The high-frequency power supply according to any one of claims 1 to 5 and 9 to 13, wherein:

the output control means makes the prescribed ratio non-zero.

15. The high-frequency power supply according to any one of claims 1 to 5 and 9 to 13, wherein:

the high-frequency synthesizing means is constituted by a hybrid circuit including a transmission transformer and a resistor for power consumption, and when there is a phase difference between the plurality of high frequencies, the resistor consumes power corresponding to the phase difference and outputs the remaining power.

Technical Field

The present invention relates to a high frequency power supply used in a plasma processing system or the like.

Background

A plasma processing system is a system in which a fluorine-based gas and a workpiece such as a semiconductor wafer or a liquid crystal substrate are enclosed in a chamber of a plasma processing apparatus, high-frequency power is supplied from a high-frequency power supply to a pair of electrodes in the chamber to cause electric discharge, and plasma of the gas is generated by the electric discharge, thereby performing a thin film forming process or an etching process on the workpiece.

Conventionally, as a high-frequency power supply for a plasma processing system, a high-frequency power supply is known which performs pulse modulation on an output of the high-frequency power supply based on a pulse modulation control signal having a lower frequency than an output frequency of high-frequency power to be output. The high-frequency power supply outputs, for example, pulsed high-frequency power, that is, high-frequency power only in a high-level period of the pulse modulation control signal, and does not output high-frequency power in a low-level period (see, for example, patent document 1).

In addition to the switching control for switching between the state of outputting the high-frequency power and the state of not outputting the high-frequency power, the 2-level control for switching the amplitude of the high-frequency power between the first level and the second level lower than the first level is also known. When 2-level control is performed, it is conceivable to switch the voltage supplied to the amplifier at 2 levels, thereby switching the power (power) output from the amplifier at 2 levels to form a pulse-like output.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-135159

Disclosure of Invention

Problems to be solved by the invention

However, it is difficult to switch the voltage supplied to the amplifier at high speed. Therefore, it is difficult to output pulsed high-frequency power with a frequency (hereinafter referred to as a pulse frequency) for switching between the first level and the second level increased. Further, it is difficult to change the voltage supplied to the amplifier at a high speed, and therefore it is also difficult to output high-frequency power with a desired waveform.

The present invention has been made in view of the above problems, and an object thereof is to provide a high-frequency power supply capable of outputting high-frequency power with a desired waveform that changes at high speed.

Means for solving the problems

The high-frequency power supply of the present invention is characterized by comprising: a high-frequency generation unit that generates a plurality of high frequencies whose phase differences can be changed; a high-frequency synthesizing unit that synthesizes the plurality of high frequencies output from the high-frequency generating unit at a predetermined ratio based on the phase difference and outputs the synthesized plurality of high frequencies to a load; and an output control unit that controls the high-frequency power output from the high-frequency combining unit by changing the phase difference with respect to the high-frequency generating unit, wherein the output control unit changes the phase difference so that the high-frequency power output from the high-frequency combining unit has a desired waveform.

In a preferred embodiment of the present invention, the output control means switches the phase difference between a first predetermined value and a second predetermined value.

In a preferred embodiment of the present invention, the predetermined ratio when the phase difference is the first predetermined value is larger than the predetermined ratio when the phase difference is the second predetermined value.

In a preferred embodiment of the present invention, the first predetermined value is 0[ deg ] or more and less than 90[ deg ], and the second predetermined value is 90[ deg ] or more and 180[ deg ] or less.

In a preferred embodiment of the present invention, the first predetermined value is 0[ deg ].

In a preferred embodiment of the present invention, the second predetermined value is 180[ deg ].

In a preferred embodiment of the present invention, the output control means performs feedback control of the high-frequency power by changing the first predetermined value or the second predetermined value.

In a preferred embodiment of the present invention, the high frequency generating means generates a first high frequency and a second high frequency, and the output control means switches a phase difference between the second high frequency and the first high frequency between the first predetermined value and the second predetermined value.

In a preferred embodiment of the present invention, the output control means switches the phase difference between a first predetermined value, a second predetermined value, and a third predetermined value.

In a preferred embodiment of the present invention, the output control means changes the phase difference according to a linear function.

In a preferred embodiment of the present invention, the output control means changes the phase difference according to the following equation,

where θ is the phase difference, and x (t) is a function representing a desired waveform.

In a preferred embodiment of the present invention, the output control means switches the phase difference between a first predetermined value and a value of a predetermined function.

In a preferred embodiment of the present invention, the output control means sets the phase difference to a phase difference that makes an output larger than an output when the phase difference is the first predetermined value and the second predetermined value when the output to the load starts.

In a preferred embodiment of the present invention, the output control means makes the predetermined ratio non-zero.

In a preferred embodiment of the present invention, the high frequency synthesizing means is constituted by a hybrid circuit including a transmission transformer and a resistor for consuming power, and when there is a phase difference between the plurality of high frequencies, the resistor consumes power corresponding to the phase difference and outputs the remaining power.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, by changing the phase difference, the waveform of the high-frequency power synthesized and output by the high-frequency synthesizing means can be changed. Since the phase difference between the plurality of high frequencies generated by the high frequency generating means can be changed at high speed, the high frequency power can be output as a desired waveform that changes at high speed.

Drawings

Fig. 1 is a block diagram showing an internal configuration of a high-frequency power supply of the present invention.

Fig. 2 is a diagram showing an example of a circuit of a DC-DC converter constituting the DC-DC converter section.

Fig. 3 is a diagram showing an example of a circuit of the DC-RF converter.

Fig. 4 is a diagram showing an example of a hybrid circuit constituting the RF combining section.

Fig. 5 is a diagram showing a relationship between the phase difference and a ratio of power synthesis in the RF synthesis unit.

Fig. 6 is a diagram showing an example of a circuit of the RF synthesizer.

Fig. 7 is a diagram showing an internal configuration of the high-frequency signal generating unit and a method of generating a high-frequency signal.

Fig. 8 is a diagram showing 2 high-frequency signals output from the high-frequency signal generating unit.

FIG. 9 shows a high-frequency voltage v output from the RF combining section_PXA graph of the waveform of (a).

Fig. 10 is a diagram showing an example of a frame configuration in a case where 3 DC-RF converters and 2 RF combiners are provided.

Fig. 11 is a diagram showing another example of the block configuration in the case where 3 DC-RF converters and 2 RF combiners are provided.

Fig. 12 is a diagram showing an example of a frame configuration in a case where 4 DC-RF converters and 3 RF combiners are provided.

Fig. 13 is a diagram showing another example of the block configuration in the case where 4 DC-RF converters and 3 RF combiners are provided.

Fig. 14 is a diagram showing an example of a circuit in a case where the RF combining unit is configured by a circuit that combines 3 or more input powers.

Fig. 15 is a diagram showing a configuration of a plasma processing system having an impedance matching apparatus.

FIG. 16 shows a high-frequency voltage v output from the RF synthesizer_PXA graph of the waveform of (a).

Detailed Description

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In particular, a high frequency power source applied to a plasma processing system will be described as an example.

Fig. 1 is a block diagram showing an internal configuration of a high-frequency power supply of the present invention.

The high-frequency power supply 1 shown in fig. 1 outputs pulsed high-frequency power having a high-level period in which the amplitude is at a first level and a low-level period in which the amplitude is at a second level lower than the first level. The high-frequency power supply 1 includes 2 power amplifiers and a power combining circuit that combines output powers of the two power amplifiers. The power combining circuit can change the combining ratio in accordance with the phase difference θ of the input 2 voltage signals from a state in which all the input power is output to 0 by heat dissipation. The high frequency power supply 1 is configured by inputting 2 high frequency voltages v to 2 power amplifiers_a、v_bThe phase difference (theta) is switched between 2 values (the first phase difference (theta 1) and the second phase difference (theta 2) (> theta 1)), so that the output from the power combining circuit becomes pulse-shaped high-frequency power. That is, the phase difference θ is set to the first phase difference θ 1 for a predetermined period, and the output from the power combining circuit is set to the first level of power (high level period), and then the phase difference θ is set to the second phase difference θ 2 for a predetermined period, so that the output from the power combining circuit is set to the second level of power (low level period), and this is repeated, and pulse-shaped high frequency power is output.

The high-frequency power supply 1 includes: an AC-DC converter 2, a DC-DC converter 3, a DC-RF converter 4, an RF synthesizer 5, a filter circuit 6, a power detector 10, a PWM signal generator 7, a high frequency signal generator 8, and a controller 9. The DC-RF converter 4 and the RF synthesizer 5 constitute a high-frequency generator U that outputs high-frequency power to a load. The DC-RF converter 4 includes 2 DC-RF converters 4A and 4B having the same configuration. Electric power P output from first DC-RF conversion unit 4A_AAnd electric power P output from the second DC-RF conversion section 4B_BAnd synthesized by the RF synthesis unit 5 and outputted to a load (plasma processing apparatus, not shown) connected to the output terminal of the high-frequency power supply 1)。

The AC-DC converter 2 generates an input voltage (DC voltage) v from the commercial power supply to the DC-DC converter 3_ccThe circuit module of (1). The AC-DC converter 2 rectifies a commercial frequency voltage input from a commercial power supply by a rectifier circuit in which 4 semiconductor rectifier elements are bridged, and smoothes the rectified level by a smoothing circuit to generate a DC voltage v_ccKnown power supply circuit configurations.

The DC-DC converter 3 converts the DC voltage v input from the AC-DC converter 2_ccDC voltage V converted to arbitrary voltage value_dcAnd outputs to the circuit block of the DC-RF conversion section 4.

The DC-DC converter unit 3 is composed of a known DC-DC converter in which a rectifier circuit is combined with an inverter, as shown in fig. 2, for example. The circuit example of fig. 2 is a circuit in which a rectifier circuit 302 is connected to an inverter 301 via a transformer T1, wherein the inverter 301 includes 4 semiconductor switching elements Q_AA bridge circuit formed by bridging. The rectifier circuit 302 is composed of 4 semiconductor rectifier devices D_AAnd a circuit in which a smoothing capacitor C is connected in parallel to the pair of output terminals. A pair of output terminals of the rectifier circuit 302 are connected to the output terminals a and a' of the DC-DC converter 3, respectively. Semiconductor switching element Q_AIn the case of using a bipolar transistor, a field effect transistor, an IGBT, etc., and a semiconductor rectifying element D_AIn which a diode is used.

DC-DC converter 3 generates PWM signal S based on PWM signal S input from PWM signal generator 7_PWM4 semiconductor switching elements Q of the inverter 301_ASwitching between an on state and an off state. Corresponding to the PWM signal S_PWMDc voltage V of duty ratio (hereinafter also referred to as PWM duty ratio)_dcIs output from the DC-DC converter 3. The larger the PWM duty cycle, the higher the DC voltage V_dcThe larger becomes.

The DC-RF converter 4 is a circuit module that converts the DC power input from the DC-DC converter 3 into a predetermined high-frequency power. The output frequency of the high-frequency power is a frequency specified for plasma processing, such as 2.0MHz or 13.56 MHz. The DC-RF converter 4 includes 2 DC-RF converters 4A and 4B having the same configuration.

The first and second DC-RF conversion sections 4A and 4B are composed of a half-bridge class D amplifier shown in fig. 3. In the class-D amplifier shown in the figure, 2 semiconductor switching elements Q of the same type are connected between a pair of power supply terminals b, b_BIn 2 semiconductor switching elements Q_BAn output circuit 401 is connected between the connection point n and the output terminal c. The output circuit 401 is a filter circuit of an L-type circuit in which a capacitor for direct current cut (cut), a capacitor, and a reactor are connected in series. The transformer T2 is configured to perform a pair of semiconductor switching elements Q_BThe driving circuit of (1). In the transformer T2, a high-frequency voltage v is input to the primary winding, a high-frequency voltage v 'having the same phase as the high-frequency voltage v is output from one secondary winding (the upper secondary winding in fig. 3), and a high-frequency power supply-v' having the opposite phase to the high-frequency voltage v is output from the other secondary winding (the lower secondary winding in fig. 3). The high-frequency voltage v' is input to one of the semiconductor switching elements Q_B(upper semiconductor switching element Q in FIG. 3_B) The high-frequency power source-v' is inputted to the other semiconductor switching element Q_B(lower semiconductor switching element Q in FIG. 3_B). The high-frequency voltage v input to the primary winding of the transformer T2 is a sinusoidal voltage having an output frequency f specified for plasma processing, such as 2.0MHz or 13.56 MHz.

The power supply terminal B and the power supply terminal B ' of the first DC-RF converter 4A are connected to the power supply terminal B and the power supply terminal B ' of the second DC-RF converter 4B, respectively, and a direct-current voltage V output from the output terminals a and a ' of the DC-DC converter 3 is supplied between the power supply terminal B and the power supply terminal B_dc. In a pair of semiconductor switching elements Q_BAn n-channel MOSFET is used, but other types of transistors such as a bipolar transistor can be used. In addition, a pair of semiconductor switching elements Q may be used_BThe structure is a complementary type combining an n-channel type and a p-channel type. In this case, the secondary winding of the transformer T2 may be one, and the high-frequency voltage v' may be input to the gates of the n-channel MOSFET and the p-channel MOSFET, respectively.

Input into the first,High-frequency voltage v of primary winding of each transformer T2 of second DC-RF converters 4A and 4B_a、v_b(the subscripts a and b denote correspondence with the first DC-RF converter 4A and the second DC-RF converter 4b, respectively-the same applies hereinafter), and are generated by the high-frequency signal generator 8. The high frequency signal generating section 8 generates a signal v_a＝A·sin(ω·t+φ_a)、v_b＝A·sin(ω·t+φ_b) High frequency voltage v of the representation_a、v_b. Note that the angular frequency ω is 2 pi f, and the angular frequency ω may be used instead of the output frequency f. High frequency voltage v_aInitial phase phi of_aFixed position 0 deg]High frequency voltage v_bInitial phase phi of_bIs variable. The high-frequency signal generation unit 8 sets the phase difference θ ═ Φ based on the phase difference input from the control unit 9_b-φ_aInformation of (d), high frequency voltage v_bInitial phase phi of_b(-) varies. The change in the phase difference θ will be described later. In addition, the initial phase phi can also be adjusted_bFixed position 0 deg]Is the initial phase phi_aIs variable, and can also be the initial phase phi_a、φ_bAre all variable. For example, the initial phase phi can be set_aIn the range from 0[ deg. ]]To-90 [ deg. ]]Is variable so that the initial phase phi_bIn the range from 0[ deg. ]]To 90[ deg. ]]Is variable in the range of 90 deg. phase difference theta]In the case of (2), can be set to φ_a＝-45[deg]、φ_b＝45[deg]。

In the first DC-RF converting section 4A, a high-frequency voltage v_aWhen a voltage a · sin (ω · T) is input to the primary winding of the transformer T2, a high-frequency voltage v in phase is output from one secondary winding of the transformer T2_a'A'. sin (ω.t) and an inverted high-frequency power supply-v is output from the other secondary winding of the transformer T2_a'-a'. sin (ω · t). High-frequency voltage v of the same phase_a' semiconductor switching element Q to be input to one side_B(upper semiconductor switching element Q in FIG. 3)_B) High frequency power supply-v of opposite phase_a' semiconductor switching element Q to be inputted to the other side_B(lower semiconductor switching element Q in FIG. 3_B). Due to 2 semiconductor switching elements Q_BIs an n-channel type MOSFET in oneSquare semiconductor switch element Q_BAt a high frequency voltage v_a' the high-level period of the transistor is turned on, and the other semiconductor switching element Q_BAt high frequency power supply-v_a' the high period conducts. I.e. 2 semiconductor switching elements Q_BAt a high frequency voltage v_aThe on/off operation of the' is repeated alternately every half cycle.

By 2 semiconductor switching elements Q_BAlternately repeating ON/OFF operations to connect the voltage v of the node n_nAccording to v_a' > 0 is changed to "V_dc", at v_aThe voltage changes in a rectangular wave shape so as to become a ground level in a period of' 0 or less. The rectangular wave is output by the output circuit 401 to remove the DC component and the switching noise, and the high frequency voltage v is output from the output terminals c and c_aAmplified high-frequency voltage v_PAAnd (V · sin (ω · t) output.

The second DC-RF converter 4B operates in the same manner as the first DC-RF converter 4A described above, and outputs the high-frequency voltage v to be input_bAmplified high-frequency voltage v_PB＝V·sin(ω·t+θ)。

In the present embodiment, the first and second DC-RF conversion sections 4A and 4B are configured by half-bridge type amplifiers, but may be configured by full-bridge type or push-pull type amplifiers. Further, the present invention is not limited to the switching amplifier, and a linear amplifier may be used.

The RF synthesis unit 5 synthesizes 2 high-frequency powers P outputted from the DC-RF conversion unit 4_A、P_BThe circuit module of (1). The RF combining unit 5 is formed by a hybrid circuit including a transmission transformer T3 and a resistor R as shown in fig. 4, for example. The hybrid circuit has 1 junction Port (サム & ポート Sum Port) N_SAnd 2 input ports N_A、N_BHaving when input to input port N_AAnd the alternating voltage input to the input port N_BWhen there is a phase difference in the ac voltage of (1), a part of the input power corresponding to the phase difference is consumed by the resistance R, and the rest of the input power is output.

As shown in fig. 4, high output from the first DC-RF conversion section 4AFrequency voltage v_PAIs input to an input port N_AA high-frequency voltage v output from the second DC-RF conversion section 4B_PBIs inputted to another input port N_BFrom the merging port N_SOutput high frequency voltage v_PX。

And a merging port N_SImpedance "R" of connected load_oFrom the merging port N in the case of/2 "(in the case of impedance matching between the RF combining section 5 and the load)_SOutput high frequency current i_PXAnd a high-frequency voltage v_PXAt a high frequency voltage v_PA、v_PBAre respectively set as v_PA＝V·sin(ω·t)、v_PBWhen V · sin (ω · t + θ), it is described as follows.

Voltage v across resistor R_RComprises the following steps:

v_R＝v_PA-v_PB＝V·[sin(ω·t)-sin(ω·t+θ)]…(1)

from input port N_A、N_BCurrent i flowing into the transmission transformer T3_A、i_BAnd a current i flowing through the resistor R_RComprises the following steps:

i_A＝v_PA/R_o＝V·sin(ω·t)/R_o…(2)

i_B＝v_PB/R_o＝V·sin(ω·t+θ)/R_o…(3)

i_R＝v_R/(2·R_o)

＝V·[sin(ω·t)-sin(ω·t+θ)]/(2·R_o)…(4)。

therefore, the current i flowing through the primary winding and the secondary winding of the transmission transformer T3 is transmitted_LA、i_LBConsists of:

i_LA＝i_A-i_R＝V·[sin(ω·t)+sin(ω·t+θ)]/(2·R_o)…(5)

i_LB＝i_B+i_R＝V·[sin(ω·t)+sin(ω·t+θ)]/(2·R_o)…(6)

from the merging port N_SOutput high frequency current i_PXAnd a high-frequency voltage v_PXThe method comprises the following steps:

i_PX＝i_LA+i_LB＝V·[sin(ω·t)+sin(ω·t+θ)]/R_o…(7)

v_PX＝i_PX·(R_o/2)

＝V·[sin(ω·t)+sin(ω·t+θ)]/2

＝V·[sin{(ω·t+θ/2)-θ/2}+sin{(ω·t+θ/2)+θ/2}]/2

＝V·[sin(ω·t+θ/2)·cos(θ/2)-cos(ω·t+θ/2)·sin(θ/2)+sin(ω·t+θ/2)·cos(θ/2)+cos(ω·t+θ/2)·sin(θ/2)]/2

＝V·cos(θ/2)·sin(ω·t+θ/2)…(8)。

when requesting the slave output port N_SOutput power P_XAnd the power P consumed by the resistor R_RThen, the following steps are carried out:

P_X＝v_PX ²/(R_o/2)＝2·v_PX ²/R_o

＝V²·[sin(ω·t)+sin(ω·t+θ)]²/(2·R_o)

＝2·[V·cos(θ/2)]²·sin²(ω·t+θ/2)/R_o…(9)

P_R＝v_R ²/(2·R_o)

＝V²·[sin(ω·t)-sin(ω·t+θ)]²/(2·R_o)

＝V²·[sin{(ω·t+θ/2)-θ/2}-sin{(ω·t+θ/2)+θ/2}]²/(2·R_o)

＝V²·[sin(ω·t+θ/2)·cos(θ/2)-cos(ω·t+θ/2)·sin(θ/2)-sin(ω·t+θ/2)·cos(θ/2)-cos(ω·t+θ/2)·sin(θ/2)]²/(2·R_o)

＝V²·[-2cos(ω·t+θ/2)·sin(θ/2)]²/(2·R_o)

＝2·[V·sin(θ/2)]²·cos²(ω·t+θ/2)/R_o…(10)。

from input port N_A、N_BInput power P_A、P_BDue to P_A＝V²·sin²(ω·t)/R_o、P_B＝V²·sin²(ω·t+θ)/R_oTherefore, the power P inputted to the RF combining section 5_inComprises the following steps: p_in＝P_A+P_B＝V²·[sin²(ω·t)+sin²(ω·t+θ)]/R_o. On the other hand, the electric power P output from the RF combining section 5_XAnd electric power P dissipated by resistance Rheat_RTotal power P of_sumThe method comprises the following steps:

P_sum＝P_X+P_R

＝V²·[sin(ω·t)+sin(ω·t+θ)]²/(2·R_o)+V²·[sin(ω·t)-sin(ω·t+θ)]²/(2·R_o)

＝V²·[2sin²(ω·t)+2sin²(ω·t+θ)]/(2·R_o)

＝V²·[sin²(ω·t)+sin²(ω·t+θ)]/R_o

thus, P_in＝P_sum。

Therefore, if θ is 0[ deg ]]Then P is_RWhen it is 0, power P is input_inRemains as it is as the output power P_XOutput from the RF synthesis section 5, if theta is 180[ deg ]]Then become P_XWhen it is 0, 0 is output from the RF synthesizer 5. And, when 0[ deg ]]<θ<180[deg]When the power P is input_A、P_BThe output power P is the synthetic power synthesized at a predetermined ratio eta (theta) corresponding to the phase difference theta_XAnd output from the RF combining section 5.

The predetermined ratio η (θ) corresponding to the phase difference θ is cos as shown in the formula (9)²(θ/2), this characteristic is as shown in characteristic (A) of FIG. 5. The electric power composition ratio eta (theta) is 0 deg]) Is 100%, when the phase difference θ becomes large, cos is increased accordingly²The characteristic of (theta/2) becomes monotonously small and the phase difference theta is 180 deg]The value of (B) is 0%. In the present embodiment, the phase difference θ is set to the first phase difference θ 1 (for example, 20[ deg ])]) With a second phase difference theta 2 (e.g. 160 deg]) Is switched so that the synthesis ratio is largeIs switched between a state of (eta 1) and a state of (eta 2) to output the electric power (P)_XThe high-frequency power is formed in a pulse shape. Further, the first phase difference θ 1 is set to 20[ deg ]]And the second phase difference theta 2 is set to 160 deg]The first phase difference θ 1 and the second phase difference θ 2 have a variation width in order to control the output power by changing the first phase difference θ 1 and the second phase difference θ 2 as described later. The first phase difference θ 1 may be set to 0[ deg ], for example]To 90[ deg. ]]The second phase difference θ 2 can be set to be, for example, from 90[ deg ]]To 180[ deg. ]]The value of (c).

In the present embodiment, the first phase difference θ 1 and the second phase difference θ 2 are set to values ranging from 0[ deg ] to 180[ deg ], but the present invention is not limited thereto. For example, the value may be set to a range from 180[ deg ] to 360[ deg ], or may be set to a range from 0[ deg ] to-180 [ deg ].

Further, the characteristic (A) of FIG. 5 is that it is connected to the merging port N_SThe impedance of the connected load is "R_oExample of the case of/2 ", but with merging port N_SImpedance of connected load even with "R_oIn the case of a difference of/2', the phase difference theta is set to be from 0[ deg ]]To 180[ deg. ]]Can also control the electric power P output from the RF combining section 5_XThe size of (2).

The hybrid circuit used in the RF combining unit 5 is not limited to the circuit configuration shown in fig. 4. For example, a hybrid circuit having the circuit configuration shown in fig. 6 may be used for the RF combining unit 5. The hybrid circuit shown in fig. 6 has a circuit configuration in which both ends of the primary winding and the secondary winding of the transmission transformer T3 are connected by the capacitor C', respectively, and 4 terminals of both ends of the primary winding and both ends of the secondary winding are unbalanced input/output terminals. When used as the RF combining unit 5, the one terminal p1 of the primary winding serves as an output terminal for combining electric power, the other terminal p2 of the primary winding and the one terminal p3 of the secondary winding serve as input terminals, and the other terminal p4 of the secondary winding serves as a terminal to which the resistor R for heat consumption is connected.

In the circuit configuration shown in FIG. 4, the phase difference θ is 0[ deg ]]In the case of the resistor RPower consumption P_RBecomes zero, but in the circuit configuration shown in FIG. 6, the phase difference θ is 90[ deg ]]In the case of (3), the power consumption P at the resistor R_RBecomes zero and the phase difference theta is from 90 deg]At the time of deviation, electric power P corresponding to the amount of deviation_RIs consumed by the resistor R. That is, in the case of the circuit configuration shown in fig. 6, the ratio η (θ) of the power combining is improved by 90[ deg ] with respect to the circuit configuration shown in fig. 4]As shown in the characteristic (B) of FIG. 5, cos is formed²(θ/2+π/2)＝sin²(theta/2). At this time, the first phase difference theta 1 and the second phase difference theta 2 are set to be from-90 deg]To 90[ deg. ]]Any value within the range of (1). In addition, for example, the value may be set from 90[ deg ]]To 270[ deg ]]A value of (d).

The RF combining unit 5 may be another circuit as long as it can function as a hybrid circuit. For example, a high-frequency power synthesizer as described in japanese patent laid-open No. 2008-28923 or an output synthesizing circuit as described in japanese utility laid-open No. 4-48715 can be used.

The filter circuit 6 is, for example, a Low Pass Filter (LPF) formed of a pi-type circuit including 2 capacitors and 1 reactor. The filter circuit 6 generates the high frequency voltage v outputted from the RF combining section 5_PXAnd a high-frequency current i_PXAnd a function of removing the harmonic wave of (4) and outputting the fundamental wave component to the load side. The filter circuit 6 is not limited to a pi-type circuit of a capacitor and a reactor as long as it is a Low Pass Filter (LPF).

The power detection unit 10 detects traveling wave power P, for example, output from the high-frequency power supply 1_fThe component (2). The power detection unit 10 includes a directional coupler, and detects a high-frequency voltage v included in the high-frequency voltage v by the directional coupler_outV of travelling wave voltage of_fAnd a reflected wave voltage v_r. And the power detection unit 10 converts the traveling wave voltage v_fConversion to travelling wave power P_fAnd outputs the result to the control unit 9. In addition, the reflected wave voltage v can be converted into the voltage v_rConverted into reflected wave power P_rAnd outputs the result to the control unit 9.

PWM signal generation unit 7 generates PWM signal S for driving DC-DC conversion unit 3_PWMAnd applying the PWM signal S_PWMOutput to DC-DC conversionAnd (3) a portion. PWM signal generation unit 7 generates PWM signal S based on a preset PWM duty ratio_PWM. When it is desired to increase the DC voltage V output from the DC-DC converter 3_dcIn the case of (3), the duty ratio is set to be large. In addition, when the direct-current voltage V output from the DC-DC converter 3 is desired to be reduced_dcIn the case of (3), the duty ratio is set to be small. The PWM duty is based on a target output power P in a high-level period of a pulse to be described later_fs1To set it. For example, with a value representing the target output power P_fs1And a table or a relational expression of the relationship with the PWM duty, and the PWM duty can be set based on the table or the relational expression. Therefore, as long as the target output power P_fs1Since the PWM duty ratio is constant without change, the DC voltage V output from the DC-DC converter 3 is_dcAnd also must be.

The high-frequency signal generation unit 8 generates and controls the semiconductor switching element Q in the first DC-RF conversion unit 4A_BOf the high-frequency voltage v of the drive_aAnd controlling the semiconductor switching element Q in the second DC-RF conversion section 4B_BOf the high-frequency voltage v of the drive_b. The high-frequency signal generator 8 generates a high-frequency voltage v based on the amplitude a, the output frequency f, and the phase difference θ input from the controller 9_a、v_bApplying a high-frequency voltage v_aThe high frequency voltage v is outputted to the first DC-RF conversion part 4A_bAnd outputs to the second DC-RF conversion section 4B.

As shown in fig. 7, the high-frequency signal generating unit 8 includes: high-frequency voltage v for generating sine wave_aThe first high-frequency generation circuit 8 a; and generating the high-frequency voltage v by using the phase difference theta input from the control unit 9_aHigh-frequency voltage v of sine wave having phase difference theta_bAnd a second high-frequency generation circuit 8 b. The first high-frequency generation circuit 8a and the second high-frequency generation circuit 8b are constituted by direct digital frequency synthesizers.

The high-frequency voltage v is input from the control unit 9 to the first high-frequency generation circuit 8a_aAmplitude a, output frequency f and initial phase phi of_a(＝0[deg]) The information of (1). The output frequency f is a frequency of 2.0MHz, 13.56MHz, or the like, which is specified in the plasma processing system, as described above. Initial phase phi_aCan be used forSet to an arbitrary value, but set to 0[ deg ] in the present embodiment]. The second high-frequency generation circuit 8b is also supplied with the high-frequency voltage v_bAmplitude a, output frequency f and initial phase phi of_bBecause theta is equal to phi_b-φ_a、φ_a＝0[deg]The phase value θ output from the control unit 9 is used as the initial phase Φ_bIs input. When set to phi_a≠0[deg]Then, the initial phase phi is added to the phase difference theta output from the control unit 9_aThe resulting value (θ + φ)_a) As an initial phase phi_bIs input. The information of the amplitude a and the output frequency f is the same as the information of the amplitude a and the output frequency f input to the first high frequency generating circuit 8 a. When the amplitude a and the output frequency f are not changed, they may be set in advance in the first high-frequency generation circuit 8a and the second high-frequency generation circuit 8 b.

The first high-frequency generation circuit 8a uses the amplitude A, the output frequency f and the initial phase phi_aGenerates a high-frequency voltage v represented by a · sin (2 pi f · t) ═ a · sin (ω · t)_a(digital signal. refer to v of FIG. 8_a). Similarly, the second high-frequency generation circuit 8b generates a high-frequency voltage v represented by a · sin (2 π f · t + θ) ═ a · sin (ω · t + θ) using the information of the amplitude a, the output frequency f, and the control command value θ_b(digital signals, see v of FIG. 8)_b)。

The control part 9 controls the traveling wave power P outputted from the high frequency power supply 1_fAnd 2 high-frequency voltages v generated by the first and second high-frequency generation circuits 8a, 8b_a、v_bA phase difference θ. The control unit 9 is constituted by a microcomputer including a cpu (central Processing unit), a rom (read Only memory), and a ram (random Access memory). The CPU executes a predetermined control program stored in the ROM to control the forward power P output from the high-frequency power supply 1_fAnd 2 high-frequency voltages v_a、v_bThe phase difference θ of (a).

The control unit 9 inputs the pulse frequency and the pulse height of the pulsed high-frequency power by an input from an input device (not shown) for inputting by a user or an automatic input based on a preset programThe duty ratio between the first level and the second level of the frequency power (hereinafter referred to as a pulse duty ratio). For example, as the pulse frequency, the high-frequency voltage v is set_a、v_bA predetermined frequency (for example, 10kHz) having a low frequency (a long period) is set to, for example, 50% as a pulse duty. The control unit 9 generates an output control signal for commanding a pulse waveform of the pulsed high-frequency power based on the pulse frequency and the pulse duty ratio. The control unit 9 switches the phase difference θ to the first phase difference θ 1 during the high level period and the second phase difference θ 2 during the low level period of the output control signal.

Since the phase difference θ becomes the first phase difference θ 1 during the high level period of the output control signal, the high frequency voltage v output from the high frequency signal generating unit 8_a、v_bBecomes a first phase difference theta 1, and the high-frequency voltage v output from the first DC-RF converter 4A_PAAnd a high-frequency voltage v output from the second DC-RF conversion section 4B_PBThe phase difference θ of (2) also becomes the first phase difference θ 1. The output power P synthesized corresponding to the first phase difference theta 1_XAnd output from the RF combining section 5. In the present embodiment, the first phase difference θ 1 is set to 20[ deg ]]Output power P during high level_XAnd becomes the electric power P to be outputted from the first DC-RF conversion part 4A_AAnd the electric power P output from the second DC-RF conversion section 4B_BSummed power P_inAbout 95% (power P)_inAbout 5% of which is consumed by the RF synthesizer 5).

In addition, since the phase difference θ becomes the second phase difference θ 2 during the low level period of the output control signal, the high-frequency voltage v output from the high-frequency signal generating unit 8_a、v_bBecomes a second phase difference theta 2, and the high-frequency voltage v output from the first DC-RF converter 4A_PAAnd a high-frequency voltage v output from the second DC-RF conversion section 4B_PBThe phase difference θ of (2) also becomes the second phase difference θ 2. The output power P synthesized corresponding to the second phase difference theta 2_XAnd output from the RF combining section 5. In this embodiment, the second phase difference θ 2 is set to 160[ deg ]]So that the output power P during the low level_XBecome electric powerP_inAbout 5% (power P)_inAbout 95% of which is consumed by the RF synthesizer 5).

Thereby, the output power P outputted from the RF combining section 5_XBecomes to have electric power P_inAbout 95% of the high level period of the sum power P_inAbout 5% of the low-level period.

FIG. 9 shows the high-frequency voltage v output from the RF synthesizer 5_PXA graph of the waveform of (a). High frequency voltage v_PXThe phase difference θ becomes a high level with a large amplitude when the phase difference θ is the first phase difference θ 1, and becomes a low level with a small amplitude when the phase difference θ is the second phase difference θ 2. Therefore, the high-frequency power P output from the RF combining section 5_XThe high frequency power is pulsed.

The control unit 9 also performs high-frequency power (forward power P) to be output from the high-frequency power supply 1 to the load_f) The control is feedback control of a control target. As a control target, a target output power P during a high level period is set_fs1And target output power P during low level_fs2. The user operates an input device (not shown) to manually input the target output power P_fs1And P_fs2Or automatically inputting the target output power P by a predetermined program_fs1And P_fs2。

The control unit 9 calculates the forward power P input from the power detection unit 10 during the high level period of the output control signal_fDetected value of and target output power P_fs1Deviation Δ P1(═ P)_fs1-P_f) Based on the deviation Δ P1, a control command value for making the deviation Δ P1 zero is generated. Then, the control unit 9 controls the forward power P by changing the first phase difference θ 1 based on the control command value_f. Thereby, feedback control is performed so that the forward power P is_fBecomes target output power P_fs1. In addition, the control unit 9 calculates the forward power P input from the power detection unit 10 during the low level period of the output control signal_fDetected value of and target output power P_fs2Deviation Δ P2(═ P)_fs2-P_f) Based on the deviation Δ P2, a deviation Δ P2 is generated to be zeroThe control instruction value of (1). The control unit 9 controls the forward power P by changing the second phase difference θ 2 based on the control command value_f. Thereby, feedback control is performed so that the forward power P is_fBecomes target output power P_fs2。

The forward electric power P may not be controlled by changing the first phase difference θ 1 and the second phase difference θ 2_fBut the direct-current voltage V outputted from the DC-DC converter section 3_dcVarying to control travelling wave power P_f. At this time, the control unit 9 outputs the generated control command value to the PWM signal generation unit 7, and the PWM signal generation unit 7 generates the PWM signal S by the triangular wave comparison method based on the control command value and the generated carrier signal_PWMAnd (4) finishing. The control unit 9 may control the output power by changing the amplitude a to be output to the high-frequency signal generation unit 8 based on the control command value.

As described above, according to the high-frequency power supply 1 of the present embodiment, the first DC-RF converter 4A and the second DC-RF converter 4B are provided in the DC-RF converter 4, and the high-frequency power P to be supplied to the first DC-RF converter 4A and the second DC-RF converter 4B is provided_A、P_BThe RF synthesis unit 5 for synthesis inputs the high frequency voltage v to the first and second DC-RF conversion units 4A and 4B_a、v_bIs switched between a first phase difference theta 1 and a second phase difference theta 2. Thereby, the output power P outputted from the RF combining section 5_XWhen the phase difference theta is the first phase difference theta 1, the electric power P is formed_inAbout 95% of the phase difference θ is the second phase difference θ 2, the electric power P is obtained_inAbout 5% of the total power is a pulse-like high-frequency power having a high-level period and a low-level period. Since the phase difference θ can be switched at high speed, it is possible to output pulsed high-frequency power with a pulse frequency increased by switching between the first level and the second level.

In addition, according to the high-frequency power supply 1 of the present embodiment, the DC voltage V output from the DC-DC converter 3_dcIs kept constant (target output power P)_fs1In a case where the voltage is constant), pulse-like high-frequency power can be output. Thus, by a DC voltage V_dcIs changed to generateOvershoot (over shot) and undershoot (undershoot) of (1) do not occur.

In the present embodiment, the traveling wave power P is used_fThe case where the control is the control target has been described as an example, but the present invention is not limited to this. For example, the high-frequency power (traveling wave power P) supplied to the load may be supplied_f-reflected wave power P_r) The control is a control target.

According to the above-described embodiment, the first DC-RF converter 4A and the second DC-RF converter 4B having the same configuration are provided as the DC-RF converter 4, and the output power P of the DC-RF converters 4A and 4B is converted into the output power P_A、P_BThe RF combining unit 5 is configured to combine the output power of each DC-RF converter, and 3 or more DC-RF converters may be provided.

Fig. 10 and 11 are diagrams showing circuit configurations of the DC-RF converter 4 ' and the RF synthesizer 5 ' in a case where 3 DC-RF converters having the same configuration are provided in the high frequency generator U '. A third DC-RF converter 4C having the same configuration as the first and second DC-RF converters 4A and 4B is added to the DC-RF converter 4 ', and a first RF synthesizer 5A and a second RF synthesizer 5B having the same configuration as the RF synthesizer 5 are provided in the RF synthesizer 5'.

The circuit configurations of fig. 10 and 11 can be regarded as configurations in which a third DC-RF converter 4C and a second RF synthesizer 5B are added to the DC-RF converter 4 and the RF synthesizer 5 shown in fig. 1, and the output power of the RF synthesizer 5A and the output power of the third DC-RF converter 4C are synthesized by the second RF synthesizer 5B.

Consider the case where 3 DC-RF conversion sections of the same structure are provided: the first method, namely: according to the output voltage v of the first and second DC-RF converters 4A, 4B of the DC-RF converter 4_PA、v_PBThe third DC-RF conversion section 4C is driven with the phase difference θ being 0, and outputs the output voltage v_PCWith respect to the output voltage v_PA、v_PBControlling the driving mode by setting the phase difference theta; and a second method, namely: the output voltage v of the second DC-RF conversion part 4B_PBRelative to the output voltage v of the first DC-RF conversion part 4A_PADriving with the phase difference theta set, andthe output voltage v of the third DC-RF conversion section 4C_PCRelative to the output voltage v of the first RF combining part 5A_PXThe phase difference ψ is set to control the driving method.

Fig. 10 shows the circuit configuration of the DC-RF converter 4 'and the RF combiner 5' in the case of the first method, and fig. 11 shows the circuit configuration of the DC-RF converter 4 'and the RF combiner 5' in the case of the second method.

In the first method shown in fig. 10, since the parts of the first and second DC-RF converters 4A and 4B and the first RF synthesizer 5A can be replaced with 1 equivalent DC-RF converter, the high-frequency generator U' is substantially the same as the high-frequency generator U (see fig. 1). That is, the first RF synthesizer 5A generates the output power P of the first DC-RF converter 4A_AAnd output power P of the second DC-RF conversion section 4B_BThe second RF combining unit 5B functions to adjust the output power P to the load according to the phase difference θ while keeping the combining function_ZThe function of (c).

When the high-frequency signal v input to the first, second and third DC-RF converters 4A, 4B and 4C is input₁、v₂、v₃Has a waveform of v₁＝A₁·sin(ω·t+φ₁)、v₂＝A₂·sin(ω·t+φ₂)、v₃＝A₃·sin(ω·t+φ₃) In the first method shown in fig. 10, for example, v is input to the first and second DC-RF converters 4A and 4B_a＝A·sin(ω·t)(A₁＝A₂＝A、φ₁＝φ₂0) high frequency signal.

When the input ports and the output ports of the RF combining units 5A and 5B are matched, the output voltages v of the first and second DC-RF converters 4A and 4B are matched_PA、v_PBBy v_PA＝v_PBThe output voltage V of the first RF synthesizer 5A is represented by V · sin (ω · t)_PXIs represented by the formula (8) v_PXAnd (V · sin (ω · t). Therefore, v is input to the third DC-RF conversion section 4C_b＝A·sin(ω·t+θ)(A₃＝A、φ₃θ), and v is output from the third DC-RF conversion section 4C_PCWhen V · sin (ω · t + θ), from the second RFThe combining section 5B outputs v_PZOutput voltage V of V · cos (θ/2) · sin (ω · t + θ/2)_PZ。

The output power P of the first and second DC-RF converters 4A and 4B_A、P_BIs synthesized without heat loss by the first RF synthesizer 5A, and is outputted (P) from the first RF synthesizer 5A_A+P_B) Electric power P of_XThe output power P is outputted to the second RF combining section 5B_XAnd output power P of the third DC-RF conversion section 4C_CThe synthesis formula represented by formula (9) is synthesized, and the output is represented by P_Z＝2·[V·cos(θ/2)]²·sin²(ω·t+θ/2)/R_oIndicated electric power P_Z。

Therefore, in the first method shown in fig. 10, the output power P of the first and second DC-RF converters 4A and 4B can be switched by switching the phase difference θ between the first phase difference θ 1 and the second phase difference θ 2_A、P_BTotal power P of_X＝(P_A+P_B) And the output power P of the third DC-RF conversion part 4C_CThe resultant amount of (2) is the electric power P_ZAnd outputs as pulsed high frequency power.

On the other hand, in the second method shown in fig. 11, the output power P to the load is adjusted by both the first RF synthesizer 5A and the second RF synthesizer 5B_Z. V is input to the first and second DC-RF converters 4A and 4B, respectively_a＝A·sin(ω·t)(φ₁0) and v_b＝A·sin(ω·t+θ)(φ₂θ), and the output voltage v is output from the first and second DC-RF converters 4A and 4B, respectively_PA＝V·sin(ω·t)、v_PBWhen V · sin (ω · t + θ), the output voltage V of the first RF synthesizer 5A is set to V · sin_PXIs represented by the formula (8) v_PXAnd (V · cos (θ/2) · sin (ω · t + θ/2).

The amplitude A is adjusted according to the phase difference theta by inputting to the third DC-RF converter 4C₃And phi₃V is_c＝A·cos(θ/2)·sin(ω·t+θ/2+ψ)(A₃＝A·cos(θ/2)、φ₃θ/2+ ψ), and an output voltage V of V · cos (θ/2) · sin (ω · t + θ/2+ ψ) is output from the third DC-RF conversion section 4C_PCIs controlled in a manner ofV is outputted from the second RF combining section 5B_PZOutput voltage V expressed by V · cos (θ/2) · cos (ψ/2) · sin (ω · t + θ/2+ ψ/2)_PZAnd output is represented by P_Z＝2·[V·cos(θ/2)·cos(ψ/2)]²·sin²(ω·t+θ/2+ψ/2)/R_oIndicated output power P_Z。

Therefore, in the second method shown in fig. 11, the electric power P can be made to be able to switch the phase difference θ between the first phase difference θ 1 and the second phase difference θ 2 by fixing the phase difference ψ, or to switch the phase difference ψ between ψ 1 and ψ 2 by fixing the phase difference θ in the opposite direction_ZAnd outputs as pulsed high frequency power. That is, the output power P of the first DC-RF conversion unit 4A is switched by switching the phase difference θ between the first phase difference θ 1 and the second phase difference θ 2_AAnd output power P of the second DC-RF conversion section 4B_BThereby enabling the electric power P to be generated_ZAnd outputs as pulsed high frequency power. Further, the output power P of the first and second DC-RF conversion sections 4A and 4B is switched by switching the phase difference ψ between ψ 1 and ψ 2_A、P_BSynthetic power P of_XAnd output power P of the third DC-RF conversion section 4C_CCan make the electric power P_ZAnd outputs as pulsed high frequency power.

Fig. 12 and 13 are diagrams showing circuit configurations of the DC-RF converter 4 "and the RF synthesizer 5" in the case where 4 DC-RF converters having the same configuration are provided in the high-frequency generator U ". A third DC-RF converter 4C and a fourth DC-RF converter 4D having the same configurations as the first and second DC-RF converters 4A and 4B are added to the DC-RF converter 4 ″, and a first RF synthesizer 5A, a second RF synthesizer 5B, and a third RF synthesizer 5C having the same configurations as the RF synthesizer 5 are provided in the RF synthesizer 5 ″.

The first RF synthesizer 5A in the RF synthesizer 5 ″ synthesizes the output power P of the first DC-RF converter 4A in the DC-RF converter 4 ″_AAnd output power P of the second DC-RF conversion section 4B_BThe second RF synthesizer 5B synthesizes the output power P of the third DC-RF converter 4C in the DC-RF converter 4 ″_CAnd the output power of the fourth DC-RF conversion section 4DForce P_D. Further, the third RF synthesizer 5C of the RF synthesizer 5 ″ synthesizes the output power P of the first RF synthesizer 5A_XAnd output power P of the second RF combining section 5B_Y。

Even in the case where 4 DC-RF conversion sections of the same structure are provided, 2 methods are considered. The first method is as follows: output voltage v at first DC-RF converting section 4A_PAAnd an output voltage v of the second DC-RF conversion section 4B_PBA phase difference theta is set therebetween, and an output voltage v of the third DC-RF converting section 4C_PCAnd an output voltage v of the fourth DC-RF conversion section 4D_PDA phase difference θ is set therebetween to perform driving. In the first method, 2 DC-RF converters 4 and RF combiners 5 shown in fig. 1 are provided, and 2 electric powers output from the two converters are combined by the third RF combiner 5C.

Fig. 12 shows the circuit configuration of the DC-RF converter 4 "and the RF synthesizer 5" in the case of the first method. High-frequency signals v input to the first to fourth DC-RF converters 4A, 4B, 4C, 4D₁、v₂、v₃、v₄Is set as v₁＝A₁·sin(ω·t+φ₁)、v₂＝A₂·sin(ω·t+φ₂)、v₃＝A₃·sin(ω·t+φ₃)、v₄＝A₄·sin(ω·t+φ₄) In the first method shown in fig. 12, the following steps are performed: v. of₁＝v_a＝A·sin(ω·t)(A₁＝A，φ₁＝0)、v₂＝v_b＝A·sin(ω·t+θ)(A₂＝A，φ₂＝θ)、v₃＝v_a＝A·sin(ω·t)(A₃＝A，φ₃＝0)、v₄＝v_b＝A·sin(ω·t+θ)(A₄＝A，φ₄＝θ)。

In the circuit configuration shown in fig. 12, the output power P of the first DC-RF conversion unit 4A is converted by the first RF combining unit 5A based on the phase difference θ_AAnd output power P of the second DC-RF conversion section 4B_BSynthesized at a predetermined ratio, and the output power P of the third DC-RF converter 4C is converted by the second RF synthesizer 5B based on the phase difference theta_CAnd a fourth DC-RF converterOutput power P of converter 4D_DSynthesized according to the specified proportion.

When the input ports of the RF combining units 5A, 5B, 5C are matched, the output power P of the first RF combining unit 5A_XAnd output power P of the second RF combining section 5B_YFrom (9) formula P_X＝P_Y＝2·V²·cos²(θ/2)·sin²(ω·t+θ/2)/R_oAnd (4) showing. Then, the third RF combining unit 5C outputs the power P_XAnd output power P_YIs synthesized without heat loss, thereby outputting P to the load from the third RF synthesizer 5C_Z＝P_X+P_Y＝4·V²·cos²(θ/2)·sin²(ω·t+θ/2)/R_oOutput power P of_Z。

Therefore, in the first method shown in fig. 12, the output power P of the first DC-RF conversion section 4A is switched by switching the phase difference θ between the first phase difference θ 1 and the second phase difference θ 2_AAnd output power P of the second DC-RF conversion section 4B_BThe resultant amount of (2) is the electric power P_XAs a pulsed high-frequency power output, the output power P of the third DC-RF converter 4C is switched_CAnd output power P of the fourth DC-RF conversion section 4D_DThe resultant amount of (2) is the electric power P_YAnd outputs as pulsed high frequency power. And, electric power P_XAnd electric power P_YThe output power P synthesized by the third RF synthesizing part 5C_ZThe high frequency power is also pulsed.

The second method is as follows: the output voltage v of the first DC-RF conversion section 4A is controlled with the same phase_PAAnd an output voltage v of the second DC-RF conversion section 4B_PBAnd the output voltage v of the third DC-RF converting section 4C is controlled in the same phase_PCAnd an output voltage v of the fourth DC-RF conversion section 4D_PDAt the output voltage v of the first RF combining part 5A_PXAnd the output voltage v of the second RF combining part 5B_PYA phase difference theta is set therebetween.

Fig. 13 shows the circuit configuration of the DC-RF converter 4 "and the RF synthesizer 5" in the case of the second method. In the circuit configuration shown in FIG. 13, the first DC-Output power P of RF converter 4A_AAnd output power P of the second DC-RF conversion section 4B_BThe output power P of the third DC-RF converter 4C is synthesized in the same manner by the second RF synthesizer 5B_CAnd output power P of the fourth DC-RF conversion section 4D_DSynthesized as is. The third RF synthesizer 5C then synthesizes the output power P of the first RF synthesizer 5A based on the phase difference θ_XAnd output power P of the second RF combining section 5B_YSynthesized according to the specified proportion.

For example, the high frequency signal v input to the first and second DC-RF converters 4A and 4B₁、v₂Is set as v₁＝v₂＝v_a＝A·sin(ω·t)(A₁＝A₂＝A，φ₁＝φ₂0), the output voltage v of the first RF combining section 5A is obtained_PXIs represented by the formula (8) v_PXAnd (V · sin (ω · t). High-frequency signals v input to the third and fourth DC-RF converters 4C and 4D₃、v₄Is set as v₃＝v₄＝v_b＝A·sin(ω·t+θ)(A₃＝A₄＝A，φ₃＝φ₄θ), the output voltage v of the second RF combining section 5B is increased_PYIs represented by the formula (8) v_PYAnd (V · sin (ω · t + θ).

Therefore, v is output from the third RF combining unit 5C according to the expression (8)_PZ＝V·cos(θ/2)·sin(ω·t+θ/2)]This output voltage v_PZAccording to the formula (9), P is outputted to the load_Z＝2·[V·cos(θ/2)]²·sin²(ω·t+θ/2)/R_oThis output power v_PZ。

Therefore, in the second method shown in fig. 13, the output power P of the first RF synthesizer 5A is switched by switching the phase difference θ between the first phase difference θ 1 and the second phase difference θ 2_X(＝P_A+P_B) And output power P of the second RF combining section 5B_Y(＝P_C+P_D) Can make the electric power P_ZAnd outputs as pulsed high frequency power.

In the embodiment shown in fig. 1, the output voltage v of the first DC-RF conversion section 4A is adjusted by_PAInitial phase phi of_aThe output voltage v of the second DC-RF converter 4B is fixed_PBInitial phase phi of_bIs varied so that the phase difference theta becomes phi_b-φ_aBy varying, but also by varying the initial phase phi_bIs fixed to make the initial phase phi_aIs varied so that the phase difference theta becomes phi_b-φ_aAnd (4) changing. Alternatively, the initial phase phi may be set_a、φ_bThe two are changed to make the phase difference theta equal to phi_b-φ_aAnd (4) changing.

In the above embodiment, the case where the RF combining unit 5 has a circuit configuration for combining 2 pieces of RF power is explained, but the RF combining unit 5 may be configured by a circuit for combining 3 or more pieces of RF power. As a circuit for combining 3 or more RF powers, for example, a circuit shown in fig. 14 can be used.

For example, when 3 pieces of RF power are synthesized using the power synthesizing circuit shown in fig. 14(b), the input voltage v input to each of the input terminals 1, 2, and 3 is input_a、v_b、v_cIs set as v_a＝A·sin(ω·t+φ_a)、v_b＝B·sin(ω·t+φ_b)、v_cC · sin (ω · t + Φ C), the effective value is v_arms、v_brms、v_crmsWhen the input power P is inputted to the power combining circuit_a＝v_arms ²/R、P_b＝v_brms ²/R、P_c＝v_crms ²and/R. If not v_a＝v_b＝v_cGenerating differential voltages v at 3 resistors R in the circuit_ab＝v_a-v_b、v_bc＝v_b-v_c、v_ca＝v_c-v_aThus, the difference voltage v_ab、v_bc、v_caIs set to v_abrms、v_bcrms、v_carmsIn each case, heat losses P are respectively realized at 3 resistors R_ab＝v_abrms ²/R、P_bc＝v_bcrms ²/R、P_ca＝v_carms ²Power of/R.

Thus, by applying a voltage at the inputv_a、v_b、v_cAre set to be out of phase with each other_ab、θ_bc、θ_caThe input power P can be synthesized by the power synthesizing circuit_in＝P_a+P_b+P_cIs a part of (P)_ab+P_bc+P_ca) The rest of the electric power P is consumed_in-(P_ab+P_bc+P_ca) And output to the load. The same applies to the case where 4 or more RF powers are input.

In the above-described embodiment, the output control of the high-frequency power supply 1 is described by taking as an example a plasma processing system in which a plasma processing apparatus is connected to the high-frequency power supply 1 as a load, but the present invention can also be applied to a case where an impedance matching apparatus 12 is provided between the high-frequency power supply 1 and the plasma processing apparatus 11, as shown in fig. 15.

In the case where the impedance matching device 12 is provided, even if the impedance (load impedance) of the plasma processing apparatus 8 fluctuates, the impedance matching between the high-frequency power supply 1 and the plasma processing apparatus 12 can be performed by the impedance matching device 12, but since the impedance matching device 12 is in a state of being unmatched during the transition period in which the impedance matching process is performed, the method of controlling the output of the high-frequency power supply 1 of the present invention is effective in the plasma processing system having the impedance matching device 12.

The gist of the above embodiment is that the high-frequency generating unit U for synthesizing a plurality of high-frequency powers is provided, and the high-frequency generating unit U outputs, for example, a pulse-like high-frequency power having a high-level period and a low-level period by switching the phase difference θ between the first phase difference θ 1 and the second phase difference θ 2.

In the above embodiment, the high-frequency voltage v to be output to the load_outThe waveform of (a) is a sine wave, but may be a trapezoidal wave or a rectangular wave having a dead time.

In the above-described embodiment, the case where the control unit 9 outputs the high-frequency power in a pulse form in which the amplitude of the high-frequency power is switched between the first level and the second level by switching the phase difference θ output to the high-frequency signal generation unit 8 between the 2 values θ 1 and θ 2 has been described, but the present invention is not limited to this. For example, the amplitude of the high-frequency power may be switched between 3 or more levels.

FIG. 16(a) shows the high-frequency voltage v outputted from the RF combining section 5_PXIs switched between 3 levels. The control unit 9 sets the phase difference θ outputted to the high frequency signal generation unit 8 to a first phase difference θ 1 (for example, 20[ deg ])]) A second phase difference theta 2 (e.g. 90 deg]) And a third phase difference theta 3 (e.g. 160 deg]) The 3 values are switched so that the high-frequency voltage v outputted from the RF combining section 5_PXThe waveform of (b) is changed by 3 levels in accordance with the waveform shown in fig. 16 (a). Therefore, the high-frequency power P output from the RF combining section 5_XThe amplitude of (c) is switched at 3 levels.

Note that the phase difference θ may be a value of a predetermined function that changes according to the time t, instead of being switched between a plurality of fixed values.

For example, when the phase difference θ is a linear function θ of the time t, a · t + b (a and b are constants), the synthesis ratio η (θ) in the RF synthesis unit 5 has a characteristic (a) shown in fig. 5, and therefore the high-frequency voltage v output from the RF synthesis unit 5 is a high-frequency voltage v_PXThe waveform of (c) changes into a sine wave like the waveform shown in fig. 16 (b). Therefore, the high-frequency power P output from the RF combining section 5_XThe variation is sinusoidal.

In addition, when it is desired to make the high-frequency power P_XWhen the waveform is changed to a desired waveform, the high-frequency voltage v may be changed to a desired waveform_PXThe phase difference θ may be changed so that the waveform of (a) is in a desired wave shape. That is, as described above, since the synthesis ratio η (θ) is (cos)²(θ/2)), the phase difference θ at the desired synthesis ratio η can be represented by the following expression (11).

Thus, for example, applying a high-frequency voltage v_PXWhen the waveform (c) is the waveform (triangular waveform) shown in FIG. 16(c), the waveform (c) is obtainedThe phase difference θ may be changed according to the time t so as to obtain the synthesis ratio η corresponding to the waveform shown in fig. 16 (c). That is, in the above equation (11), the synthesis ratio η may be a function x (t) representing the waveform shown in fig. 16 (c). If this concept is applied, the synthesis ratio η can be freely set. For example, a triangular waveform and a waveform of a constant level may be combined as shown in fig. 16(d), or a sinusoidal waveform and a waveform of a constant level may be combined as shown in fig. 16 (e).

In fig. 16(b) to (e), the synthesis ratio η (θ) in the RF synthesis unit 5 may become zero, and the output may become zero. If it is not desired that the output becomes zero, the calculation formula of the phase difference θ is adjusted so that the phase difference θ does not become 180[ deg ].

In addition, the high-frequency voltage v can be adjusted_PXThe waveform of (b) is formed to have a waveform with an overshoot at the time of plasma ignition, among the waveforms shown in fig. 9 (see fig. 16 (f)). In order to form such a waveform, the phase difference θ is repeatedly set to the first phase difference θ 1 (for example, 20[ deg ])]) And the phase difference theta is made to be the second phase difference theta 2 (e.g. 160 deg. [ deg. ])]) In the waveform of the second period t2, a third period t3 is provided before the first period t1 in order to provide an overshoot at the time of plasma ignition, and the phase difference θ may be set to the following expression (12) in the third period t3, for example. T is the length of the third period T3. This can be formed as follows: at the time of plasma ignition (at the start of the third period T3: T: 0), the phase difference θ is 0, the synthesis ratio η is maximum, the phase difference θ increases and the synthesis ratio η decreases during the third period T3, and the phase difference θ becomes θ 1 at the end of the third period T3 (T: T). During the third period t3, the phase difference θ may be set to "0". By applying a high-frequency voltage v_PXIs formed into a waveform containing the overshoot shown in fig. 16(f), and a high-frequency voltage v is outputted to the load when the plasma is not ignited_outThis increases the ignition quality of the plasma.

θ＝(θ1/T)·t…(12)

The waves shown in FIG. 16The calculation expressions such as the expression (12) and the equation (12) are examples, and the high-frequency voltage v output from the RF synthesizer 5 can be adjusted by appropriately setting the phase difference θ_PXThe waveforms of (a) and (b) are various waveforms, and the high-frequency power P outputted from the RF combining section 5 can be made to be high-frequency power_XBecomes a desired waveform.

The high-frequency power supply of the present invention is not limited to the above-described embodiments. The specific structure of each part of the high-frequency power supply of the present invention can be changed in various ways.

Description of the reference numerals

1 high frequency power supply

2 AC-DC conversion section

3 DC-DC converter

4. 4 ', 4' DC-RF converter (high frequency generator)

4A first DC-RF converter (high frequency generating means)

4B second DC-RF converter (high frequency generating means)

4C third DC-RF converter (high frequency generating means)

4D fourth DC-RF converter (high frequency generating means)

401 low-pass filter

5. 5 ', 5' RF synthesis part (high frequency synthesis unit)

5A first RF synthesizer (high frequency synthesizer)

5B second RF synthesizer (high frequency synthesizer)

5C third RF synthesizer (high frequency synthesizer)

6 filter circuit

7 PWM signal generating section

8 high-frequency Signal generating section (high-frequency generating means)

8a first high-frequency generating circuit

8b second high-frequency generating circuit

9 control part (output control unit)

10 electric power detection unit

11 plasma processing apparatus

12 impedance matching device

U, U 'and U' high frequency generation part.