High frequency power supply

Abstract

The present invention provides a high-frequency power supply that can output high-frequency power as a desired waveform that changes rapidly. The high-frequency power supply 1 includes two DC-RF converters 4A and 4B and an RF synthesizer 5 that synthesizes the outputs of the two DC-RF converters 4A and 4B. The DC-RF converters 4A and 4B respectively generate a high-frequency voltage v input from a high-frequency signal generator 8. a 、v b Amplify the output high frequency voltage v PA 、v PB RF synthesis unit 5 with high frequency voltage v PA 、v PB The phase difference θ corresponds to the synthetic proportional output high-frequency voltage v PX The control unit 9 switches the phase difference θ between θ1 and θ2. As a result, the output power P output from the RF synthesizer 5 is X The high-frequency power is pulsed and has a high-level period and a low-level period. The phase difference θ can be switched at high speed, so the high-frequency power can be output with a high switching frequency between the first level and the second level.

Description

[0001] This case is a divisional application of a patent application with an application date of December 9, 2015, application number 201580067392.6 (international application number PCT / JP2015 / 084502), and invention name “High Frequency Power Supply”. Technical Field

[0002] The present invention relates to a high frequency power supply for use in a plasma processing system or the like. Background Art

[0003] A plasma processing system, for example, is a system in which fluorine-based gas and workpieces such as semiconductor wafers and liquid crystal substrates are sealed in a chamber of a plasma processing device, and high-frequency power is supplied from a high-frequency power supply to a pair of electrodes in the chamber to cause discharge, thereby generating gas plasma through the discharge, thereby performing thin film formation or etching processing on the workpiece.

[0004] In the prior art, as a high-frequency power supply for a plasma processing system, there is known a high-frequency power supply that performs pulse modulation on the output of the high-frequency power supply according to a pulse modulation control signal having a frequency lower than the output frequency of the high-frequency power to be output. For example, the high-frequency power supply outputs pulsed high-frequency power, that is, the high-frequency power is output only during the high-level period of the pulse modulation control signal, and the high-frequency power is not output during the low-level period (for example, refer to Patent Document 1).

[0005] In addition, not only switch control for switching between a state of outputting high-frequency power and a state of not outputting high-frequency power, but also two-level control for switching the amplitude of high-frequency power between a first level and a second level lower than the first level is also known. In the case of two-level control, it can be considered that the voltage supplied to the amplifier is switched at two levels, thereby switching the power (power) output from the amplifier at two levels, forming a pulsed output.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2013-135159 Summary of the invention

[0009] Problems to be solved by the invention

[0010] However, it is difficult to switch the voltage supplied to the amplifier at high speed. Therefore, it is difficult to output high-frequency power in a pulse shape with a higher frequency (hereinafter referred to as pulse frequency) of switching between the first level and the second level. In addition, since it is difficult to change the voltage supplied to the amplifier at high speed, it is also difficult to output high-frequency power with a desired waveform.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a high-frequency power supply capable of outputting high-frequency power in a desired waveform that changes at high speed.

[0012] Methods for solving problems

[0013] The high-frequency power supply of the present invention is characterized in that it includes: a high-frequency generating unit, which generates a plurality of high frequencies whose phase differences can be changed; a high-frequency synthesizing unit, which synthesizes the plurality of high frequencies output from the high-frequency generating unit at a specified ratio based on the above-mentioned phase difference, and outputs it to a load; and an output control unit, which controls the high-frequency power output from the above-mentioned high-frequency synthesizing unit by changing the above-mentioned phase difference for the above-mentioned high-frequency generating unit, wherein the above-mentioned output control unit changes the above-mentioned phase difference so that the high-frequency power output from the above-mentioned high-frequency synthesizing unit becomes a desired waveform.

[0014] In a preferred embodiment of the present invention, the output control unit switches the phase difference between a first predetermined value and a second predetermined value.

[0015] In a preferred embodiment of the present invention, the predetermined ratio when the phase difference is the first predetermined value is greater than the predetermined ratio when the phase difference is the second predetermined value.

[0016] In a preferred embodiment of the present invention, the first predetermined value is greater than or equal to 0 [deg] and less than or equal to 90 [deg], and the second predetermined value is greater than or equal to 90 [deg] and less than or equal to 180 [deg].

[0017] In a preferred embodiment of the present invention, the first predetermined value is 0 [deg].

[0018] In a preferred embodiment of the present invention, the second predetermined value is 180 [deg].

[0019] 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.

[0020] In a preferred embodiment of the present invention, the high frequency generating unit generates a first high frequency and a second high frequency, and the output controlling unit switches a phase difference of the second high frequency with respect to the first high frequency between the first predetermined value and the second predetermined value.

[0021] In a preferred embodiment of the present invention, the output control unit switches the phase difference between a first predetermined value, a second predetermined value, and a third predetermined value.

[0022] In a preferred embodiment of the present invention, the output control unit changes the phase difference according to a linear function.

[0023] In a preferred embodiment of the present invention, the output control unit changes the phase difference according to the following formula:

[0024]

[0025] Here, θ is the above-mentioned phase difference, and x(t) is a function representing a desired waveform.

[0026] In a preferred embodiment of the present invention, the output control unit switches the phase difference between a first predetermined value and a value of a predetermined function.

[0027] In a preferred embodiment of the present invention, the output control means sets the phase difference to a phase difference that makes the output larger than the output when the phase difference is the first predetermined value and the second predetermined value when starting the output to the load.

[0028] In a preferred embodiment of the present invention, the output control means makes the predetermined ratio non-zero.

[0029] In a preferred embodiment of the present invention, the high frequency synthesis unit is composed of a hybrid circuit including a transmission transformer and a resistor for power consumption. When there is a phase difference between the multiple high frequencies, the resistor consumes power corresponding to the phase difference and outputs the remaining power.

[0030] Effects of the Invention

[0031] According to the present invention, the waveform of the high frequency power synthesized and output by the high frequency synthesizing unit can be changed by changing the phase difference. Since the phase difference between the multiple high frequencies generated by the high frequency generating unit can be changed rapidly, the high frequency power can be output as a desired waveform that changes rapidly. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a block diagram showing the internal structure of the high-frequency power supply of the present invention.

[0033] Figure 2 It is a diagram showing a circuit example of a DC-DC converter constituting a DC-DC conversion unit.

[0034] Figure 3 It is a diagram showing a circuit example of a DC-RF conversion unit.

[0035] Figure 4 This is a diagram showing an example of a mixing circuit constituting the RF synthesis unit.

[0036] Figure 5It is a diagram showing the relationship between the phase difference and the power synthesis ratio in the RF synthesis unit.

[0037] Figure 6 It is a diagram showing a circuit example of an RF synthesizer.

[0038] Figure 7 It is a diagram showing the internal structure of the high-frequency signal generating unit and a method of generating a high-frequency signal.

[0039] Figure 8 It is a diagram showing two high-frequency signals output from the high-frequency signal generating unit.

[0040] Fig. 9 is the high frequency voltage v output from the RF synthesis unit PX Graph of the waveform.

[0041] Fig.10 This is a diagram showing a block configuration example in which three DC-RF converters and two RF synthesizers are provided.

[0042] Fig.11 This is a diagram showing another block configuration example in which three DC-RF conversion units and two RF synthesis units are provided.

[0043] Fig.12 This is a diagram showing a block configuration example in which four DC-RF conversion units and three RF synthesis units are provided.

[0044] Fig.13 This is a diagram showing another block configuration example in which four DC-RF conversion units and three RF synthesis units are provided.

[0045] Fig.14 This is a diagram showing a circuit example in which the RF combining unit is constituted by a circuit for combining three or more input powers.

[0046] Fig.15 It is a diagram showing the structure of a plasma processing system having an impedance matching device.

[0047] Fig.16 is the high frequency voltage v output from the RF synthesis unit PX Graph of the waveform. DETAILED DESCRIPTION

[0048] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, and in particular, a high-frequency power supply suitable for a plasma processing system will be described as an example.

[0049] Figure 1 It is a block diagram showing the internal structure of the high-frequency power supply of the present invention.

[0050] Figure 1The high-frequency power supply 1 shown outputs a pulsed high-frequency power having a high-level period in which the amplitude is a first level and a low-level period in which the amplitude is a second level lower than the first level. The high-frequency power supply 1 has two power amplifiers and a power synthesis circuit that synthesizes the output power of the two power amplifiers. The power synthesis circuit can change the synthesis ratio according to the phase difference θ between the two input voltage signals from a state in which all the input power is output to a state in which all the output is 0 due to heat consumption. The high-frequency power supply 1 synthesizes the two high-frequency voltages v input to the two power amplifiers. a 、v b The phase difference θ is switched between two values ​​(a first phase difference θ1 and a second phase difference θ2 (>θ1)) so that the output from the power synthesis circuit becomes a pulsed high-frequency power. That is, by making the phase difference θ the first phase difference θ1 during a predetermined period, the output from the power synthesis circuit becomes a first-level power (a high-level period), and then by making the phase difference θ the second phase difference θ2 during a predetermined period, the output from the power synthesis circuit becomes a second-level power (a low-level period), and by repeating this process, a pulsed high-frequency power is output.

[0051] 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 detection unit 10, a PWM signal generator 7, a high frequency signal generator 8, and a control unit 9. The part including the DC-RF converter 4 and the RF synthesizer 5 constitutes a high frequency generator U that outputs high frequency power to a load. The DC-RF converter 4 includes two DC-RF converters 4A and 4B of the same structure. The power P outputted from the first DC-RF converter 4A is A and the power P output from the second DC-RF converter 4B B , synthesized by the RF synthesizer 5 and output to a load (plasma processing device, not shown) connected to the output end of the high frequency power supply 1.

[0052] The AC-DC converter 2 generates an input voltage (DC voltage) v from the commercial frequency power supply to the DC-DC converter 3. cc The AC-DC converter 2, for example, rectifies the power frequency voltage input from the power frequency power supply by a rectifier circuit having four semiconductor rectifier elements connected in a bridge connection, and smoothes the rectified voltage level by a smoothing circuit to generate a DC voltage v cc A known power supply circuit is formed.

[0053] The DC-DC converter 3 converts the DC voltage v input from the AC-DC converter 2 cc Convert to any voltage value DC voltage V dc , and output to the circuit module of the DC-RF conversion unit 4.

[0054] The DC-DC converter 3 is composed of, for example, Figure 2 The structure shown is a known DC-DC converter in which a rectifier circuit is combined with an inverter. Figure 2 The circuit example is a circuit in which an inverter 301 is connected to a rectifier circuit 302 via a transformer T1, wherein the inverter 301 is composed of four semiconductor switching elements Q A The rectifier circuit 302 is composed of four semiconductor rectifier elements D A A circuit in which a pair of output terminals of the rectifier circuit 302 are connected in parallel to the output terminals a and a′ of the DC-DC converter 3. The semiconductor switching element Q A In the process, bipolar transistors, field effect transistors, IGBTs, etc. are used, and semiconductor rectifier elements D A Diodes are used in.

[0055] The DC-DC converter 3 generates a PWM signal based on the PWM signal S input from the PWM signal generator 7. PWM , the four semiconductor switching elements Q of the inverter 301 A Switches between the on state and the off state. Corresponding to the PWM signal S PWM The duty cycle (hereinafter also referred to as PWM duty cycle) of the DC voltage V dc The DC voltage V dc Becoming bigger.

[0056] The DC-RF converter 4 is a circuit module that converts the DC power input from the DC-DC converter 3 into a preset high-frequency power. The output frequency of the high-frequency power is a frequency specified for plasma processing such as 2.0 MHz or 13.56 MHz. The DC-RF converter 4 is provided with two DC-RF converters 4A and 4B having the same structure.

[0057] The first and second DC-RF converters 4A and 4B are composed of Figure 3 The half-bridge D-class amplifier shown in the figure has two semiconductor switching elements Q of the same type connected between a pair of power supply terminals b and b'. B In a series circuit, two semiconductor switching elements Q B The 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 DC cutoff, a capacitor and a reactor are connected in series. The transformer T2 is composed of a pair of semiconductor switching elements Q BIn transformer T2, a high-frequency voltage v is input to the primary winding, and a secondary winding ( Figure 3 The secondary winding on the upper middle side) outputs a high-frequency voltage v' in phase with the high-frequency voltage v, and the secondary winding on the other side ( Figure 3 The secondary winding on the lower middle side outputs a high-frequency power supply -v' that is in phase with the high-frequency voltage v. The high-frequency voltage v' is input to one semiconductor switching element Q B ( Figure 3 The upper semiconductor switching element Q B ), the high frequency power -v' is input to the other semiconductor switching element Q B ( Figure 3 The semiconductor switching element Q on the lower side of 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 2.0 MHz or 13.56 MHz.

[0058] 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 the DC 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 B Although n-channel MOSFET is used, other types of transistors such as bipolar transistors can also be used. In addition, a pair of semiconductor switching elements Q B The configuration is a complementary type combining n-channel type and 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.

[0059] The high frequency voltage v input to the primary winding of each transformer T2 of the first and second DC-RF converters 4A and 4B is a 、v b (the subscripts a and b indicate that they correspond to the first DC-RF converter 4A and the second DC-RF converter 4B, respectively. The same applies to the following). The high-frequency signal generator 8 generates the high-frequency signal generated by v a =A·sin(ω·t+φ a ),v b =A·sin(ω·t+φ b ) represents the high frequency voltage v a 、v b In addition, the angular frequency is ω = 2πf, and there are also cases where the angular frequency ω is used instead of the output frequency f. High-frequency voltage v a The initial phase φa Fixed position 0[deg], high frequency voltage v b The initial phase φ b The high frequency signal generation unit 8 is based on the phase difference θ=φ input from the control unit 9. b -φ a information, so that the high frequency voltage v b The initial phase φ b (=θ) changes. The change of the phase difference θ will be described later. In addition, the initial phase φ can also be b Fixed position 0[deg], is the initial phase φ a is variable, or the initial phase φ a ,φ b For example, the initial phase φ can be changed a The initial phase φ is variable in the range from 0[deg] to -90[deg]. b The range is variable from 0[deg] to 90[deg]. When the phase difference θ=90[deg], it can be set to φ a =-45[deg], φ b =45[deg].

[0060] In the first DC-RF converter 4A, the high frequency voltage v a =A·sin(ω·t) is input to the primary winding of transformer T2, and a high-frequency voltage v with the same phase is output from one secondary winding of transformer T2. a '=A'·sin(ω·t), the other secondary winding of transformer T2 outputs the reverse-phase high-frequency power -v a '=-A'·sin(ω·t). The high frequency voltage v a ' is input to the semiconductor switching element Q on one side B (exist Figure 3 Semiconductor switch element Q on the upper middle side B ), inverted high frequency power supply -v a ' is input to the other semiconductor switching element Q B (exist Figure 3 Semiconductor switch element Q on the lower middle side B ). Since the two semiconductor switching elements Q B It is an n-channel MOSFET, in which the semiconductor switching element Q B At high frequency voltage v a ' is turned on during the high level period, and the other semiconductor switch element Q B In high frequency power supply -v a That is, the two semiconductor switch elements Q B At high frequency voltage va The on / off operation is repeated alternately in each half cycle of the circuit.

[0061] Through two semiconductor switching elements Q B The on / off operation is repeated alternately, and the voltage v at the connection point n n According to the v a '>0 during the period of "V dc ”, in v a '≤0, the rectangular wave changes in a manner that the ground level is reached. The rectangular wave is removed from the DC component and the switching noise by the output circuit 401, and the high-frequency voltage v is output from the output terminals c and c'. a The amplified high frequency voltage v PA =V·sin(ω·t) output.

[0062] The second DC-RF converter 4B performs the same operation as the first DC-RF converter 4A, and outputs a high-frequency voltage v b The amplified high frequency voltage v PB =V·sin(ω·t+θ).

[0063] In the present embodiment, the first and second DC-RF converters 4A and 4B are formed by half-bridge amplifiers, but may be formed by full-bridge or push-pull amplifiers. In addition, the amplifier is not limited to a switching amplifier, and a linear amplifier may be used.

[0064] The RF synthesizer 5 synthesizes the two high frequency powers P output from the DC-RF converter 4. A , P B The RF synthesis unit 5 is, for example, Figure 4 The hybrid circuit shown is composed of a transmission transformer T3 and a resistor R. The hybrid circuit has a sum port N S and 2 input ports N A 、N B , when input to input port N A The AC voltage and input to the input port N B When there is a phase difference in the AC voltage, a portion of the input power corresponding to the phase difference is consumed by the resistor R as heat, and the rest of the power is output.

[0065] like Figure 4 As shown, the high frequency voltage v output from the first DC-RF conversion unit 4A PA is input to an input port N A , the high frequency voltage v output from the second DC-RF converter 4B PB is input to another input port N B, from the confluence port N S Output high frequency voltage v PX .

[0066] With the confluence port N S The impedance of the connected load "R o / 2" (when the RF combiner 5 and the load are impedance matched), from the confluence port N S The output high frequency current i PX and high frequency voltage v PX , when the high frequency voltage v PA 、v PB Set to v PA =V·sin(ω·t),v PB =V·sin(ω·t+θ), it becomes as follows.

[0067] The voltage across the resistor R is v R for:

[0068] v R =v PA -v PB =V·[sin(ω·t)-sin(ω·t+θ)]…(1)

[0069] From input port N A 、N B The current i flowing into the transmission transformer T3 A 、i B and the current i flowing through the resistor R R for:

[0070] i A =v PA / R o =V·sin(ω·t) / R o …(2)

[0071] i B =v PB / R o =V·sin(ω·t+θ) / R o …(3)

[0072] i R =v R / (2·R o )

[0073] =V·[sin(ω·t)-sin(ω·t+θ)] / (2·R o )…(4).

[0074] Therefore, the current i flowing through the primary winding and secondary winding of the transmission transformer T3 is LA 、iLB Depend on:

[0075] i LA =i A -i R =V·[sin(ω·t)+sin(ω·t+θ)] / (2·R o )…(5)

[0076] i LB =i B +i R =V·[sin(ω·t)+sin(ω·t+θ)] / (2·R o )…(6)

[0077] To indicate that from the confluence port N S The output high frequency current i PX and high frequency voltage v PX become:

[0078] i PX =i LA +i LB =V·[sin(ω·t)+sin(ω·t+θ)] / R o …(7)

[0079] v PX =i PX ·(R o / 2)

[0080] =V·[sin(ω·t)+sin(ω·t+θ)] / 2

[0081] =V·[sin{(ω·t+θ / 2)-θ / 2}+sin{(ω·t+θ / 2)+θ / 2}] / 2

[0082] =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

[0083] =V·cos(θ / 2)·sin(ω·t+θ / 2)…(8).

[0084] When the output port N S Output power P X and the power P consumed by the resistor R R When, it becomes:

[0085] P X =v PX 2 / (R o / 2)=2·v PX 2 / R o

[0086] =V 2 ·[sin(ω·t)+sin(ω·t+θ)] 2 / (2·R o )

[0087] =2·[V·cos(θ / 2)] 2 ·sin 2 (ω·t+θ / 2) / R o …(9)

[0088] P R =v R 2 / (2·R o )

[0089] =V 2 ·[sin(ω·t)-sin(ω·t+θ)] 2 / (2·R o )

[0090] =V 2 ·[sin{(ω·t+θ / 2)-θ / 2}-sin{(ω·t+θ / 2)+θ / 2}] 2 / (2·R o )

[0091] =V 2 ·[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 )

[0092] =V 2 ·[-2cos(ω·t+θ / 2)·sin(θ / 2)] 2 / (2·R o )

[0093] =2·[V·sin(θ / 2)] 2 ·cos 2 (ω·t+θ / 2) / R o …(10).

[0094] From input portN A 、N B input powerP A 、P B , due to PA =V 2 ·sin 2 (ω·t) / R o , P B =V 2 ·sin 2 (ω·t+θ) / R o , so the power P input to the RF synthesis unit 5 in For: P in =P A +P B =V 2 ·[sin 2 (ω·t)+sin 2 (ω·t+θ)] / R o On the other hand, the power P output from the RF synthesizer 5 X and the power P consumed by the resistor R R Total power P sum become:

[0095] P sum =P X +P R

[0096] =V 2 [sin(ω·t)+sin(ω·t+θ)] 2 / (2·R o )+V 2 [sin(ω·t)-sin(ω·t+θ)] 2 / (2·R o )

[0097] =V 2 ·[2sin 2 (ω·t)+2sin 2 (ω·t+θ)] / (2·R o )

[0098] =V 2 ·[sin 2 (ω·t)+sin 2 (ω·t+θ)] / R o

[0099] Therefore, P in =P sum .

[0100] Therefore, if θ=0[deg], then P R =0, input power P in Keep the output power P X , output from the RF synthesis unit 5, if θ = 180 [deg], it becomes PX =0, and the RF synthesizer 5 outputs 0. Also, when 0[deg]<θ<180[deg], the input power P A , P B The combined power synthesized at a predetermined ratio η(θ) corresponding to the phase difference θ is the output power P X Output from the RF synthesis unit 5.

[0101] The prescribed ratio η(θ) corresponding to the phase difference θ is as shown in formula (9): cos 2 (θ / 2), the characteristic becomes Figure 5 The power synthesis ratio η(θ) is 100% when the phase difference θ is 0[deg], and when the phase difference θ increases, the corresponding cos 2 The characteristic of (θ / 2) decreases monotonically and becomes 0% when the phase difference θ is 180 [deg]. In this embodiment, the phase difference θ is switched between a first phase difference θ1 (e.g., 20 [deg]) and a second phase difference θ2 (e.g., 160 [deg]), thereby switching the synthesis ratio between a large state η (θ1) and a small state η (θ2), and the output power P is changed. X The high-frequency power is formed into a pulsed shape. In addition, the first phase difference θ1 is set to 20 [deg], and the second phase difference θ2 is set to 160 [deg], so as to control the output power by changing the first phase difference θ1 and the second phase difference θ2 as described later, and the first phase difference θ1 and the second phase difference θ2 have a variation range. In addition, the first phase difference θ1 can be set to a value from 0 [deg] to 90 [deg], for example, and the second phase difference θ2 can be set to a value from 90 [deg] to 180 [deg], for example.

[0102] In addition, in the present embodiment, the first phase difference θ1 and the second phase difference θ2 are set to values ​​ranging from 0 [deg] to 180 [deg], but are not limited thereto. For example, they may be set to values ​​ranging from 180 [deg] to 360 [deg], or they may be set to values ​​ranging from 0 [deg] to -180 [deg].

[0103] also, Figure 5 The characteristic (A) is, with the confluence port N S The impedance of the connected load is "R o / 2”, but with the junction port N S Even if the impedance of the connected load is equal to "R o When the phase difference θ is changed from 0 [deg] to 180 [deg], the power P output from the RF synthesizer 5 can be controlled. X size.

[0104] The hybrid circuit used in the RF synthesizer 5 is not limited to Figure 4 For example, it is also possible to Figure 6 The hybrid circuit of the circuit structure shown is used in the RF synthesizer 5 . Figure 6 The hybrid circuit shown has a circuit structure in which both ends of the primary winding and the secondary winding of the transmission transformer T3 are connected by capacitors C', respectively, and four terminals at both ends of the primary winding and the secondary winding become unbalanced input and output terminals. When used as an RF synthesizer 5, one terminal p1 of the primary winding becomes an output terminal of the synthesized power, the other terminal p2 of the primary winding and one terminal p3 of the secondary winding become input terminals, and the other terminal p4 of the secondary winding becomes a terminal connected to a resistor R for heat dissipation.

[0105] Figure 4 In the circuit configuration shown, when the phase difference θ is 0 [deg], the power consumption P of the resistor R R becomes zero, but in Figure 6 In the circuit configuration shown, when the phase difference θ is 90 degrees, the power consumption P of the resistor R R When the phase difference θ deviates from 90 degrees, the power P corresponding to the deviation is R is consumed by resistor R. That is, Figure 6 In the case of the circuit configuration shown in the figure, the ratio η(θ) of the power synthesis is Figure 4 The circuit structure shown is increased by 90[deg], such as Figure 5 The characteristic (B) shows that it becomes cos 2 (θ / 2+π / 2)=sin 2 (θ / 2) characteristics. In this case, the first phase difference θ1 and the second phase difference θ2 may be set to values ​​ranging from -90 [deg] to 90 [deg]. Alternatively, for example, they may be set to values ​​ranging from 90 [deg] to 270 [deg].

[0106] The RF synthesizer 5 may be any other circuit as long as it can function similarly to the mixer circuit. For example, a high frequency power synthesizer as described in Japanese Unexamined Patent Application Publication No. 2008-28923 or an output synthesizer as described in Japanese Utility Model Application Publication No. 4-48715 may be used.

[0107] The filter circuit 6 is a low-pass filter (LPF) composed of, for example, a π-type circuit of two capacitors and one reactor. The filter circuit 6 generates a high-frequency voltage v output from the RF synthesizer 5. PX and high frequency current i PXThe filter circuit 6 has the function of removing the harmonics and outputting the fundamental wave component to the load side. In addition, as long as the filter circuit 6 is a low-pass filter (LPF), it is not limited to a π-type circuit of a capacitor and a reactor.

[0108] The power detection unit 10 detects the traveling wave power P outputted by the high frequency power source 1. f The power detection unit 10 includes a directional coupler, which detects the power contained in the high-frequency voltage v out The traveling wave voltage v f and the reflected wave voltage v r The power detection unit 10 converts the traveling wave voltage v f Converted into traveling wave power P f And output to the control unit 9. In addition, the reflected wave voltage v r Converted into reflected wave power P r Output to the control unit 9.

[0109] The PWM signal generating unit 7 generates a PWM signal S for driving the DC-DC converter 3. PWM , and the PWM signal S PWM The PWM signal generating unit 7 generates a PWM signal S according to a preset PWM duty ratio. PWM When you want to increase the DC voltage V output from the DC-DC converter 3 dc In the case of, the duty ratio is set larger. In addition, if you want to reduce the DC voltage V output from the DC-DC converter 3 dc In the case of , the duty ratio is set to be smaller. In addition, the above-mentioned PWM duty ratio is based on the target output power P during the high level period of the pulse described later. fs1 For example, the target output power P fs1 The PWM duty ratio can be set according to the table or relational expression of the relationship between the target output power P and the PWM duty ratio. fs1 If there is no change, the PWM duty ratio is constant, so the DC voltage V output from the DC-DC converter 3 is dc Definitely.

[0110] The high frequency signal generating unit 8 generates a signal to control the semiconductor switch element Q in the first DC-RF conversion unit 4A. B The high frequency voltage v of the drive a and controls the semiconductor switching element Q in the second DC-RF conversion unit 4B B The high frequency voltage v of the drive b The high-frequency signal generating unit 8 generates a high-frequency voltage v based on the amplitude A, output frequency f, and phase difference θ input from the control unit 9. a 、v b, the high frequency voltage v a The output is sent to the first DC-RF conversion unit 4A, which converts the high frequency voltage v b The output is sent to the second DC-RF conversion unit 4B.

[0111] In the high frequency signal generating unit 8, as Figure 7 As shown, it includes: generating a high-frequency voltage v of a sine wave a and using the phase difference θ input from the control unit 9 to generate a high frequency voltage v a A high-frequency voltage v of a sinusoidal wave with a phase difference of θ b The first high frequency generating circuit 8a and the second high frequency generating circuit 8b are composed of direct digital frequency synthesizers.

[0112] A high-frequency voltage v is input from the control unit 9 to the first high-frequency generating circuit 8a. a The amplitude A, output frequency f and initial phase φ a The output frequency f is the frequency of 2.0 MHz, 13.56 MHz, etc. specified in the plasma processing system as described above. The initial phase φ a It can be set to any value, but is set to 0 [deg] in this embodiment. The high-frequency voltage v is also input to the second high-frequency generating circuit 8b. b The amplitude A, output frequency f and initial phase φ b information, since θ=φ b -φ a ,φ a = 0[deg], the phase value θ output from the control unit 9 is used as the initial phase φ b When φ is set a ≠0[deg], the phase difference θ output from the control unit 9 is added to the initial phase φ a The obtained value (θ+φ a ) as the initial phase φ b 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 8a. In addition, when the amplitude A and the output frequency f are not changed, they can also be preset in the first high-frequency generating circuit 8a and the second high-frequency generating circuit 8b.

[0113] The first high frequency generating circuit 8a uses the amplitude A, output frequency f and initial phase φ a The information generates a high-frequency voltage v represented by A·sin(2πf·t)=A·sin(ω·t) a (Digital signal. Refer to Figure 8 V a). Similarly, the second high-frequency generating circuit 8b generates a high-frequency voltage v represented by A·sin(2πf·t+θ)=A·sin(ω·t+θ) using information of the amplitude A, the output frequency f and the control command value θ. b (Digital signal, see Figure 8 V b ).

[0114] The control unit 9 controls the traveling wave power P output by the high frequency power source 1. f , and the two high frequency voltages v generated by the first and second high frequency generating circuits 8a and 8b a 、v b The control unit 9 is composed of a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory) and a RAM (Random Access Memory). The CPU controls the traveling wave power P output by the high-frequency power supply 1 by executing a predetermined control program stored in the ROM. f and 2 high frequency voltages v a 、v b The phase difference θ, etc.

[0115] The control unit 9 inputs the pulse frequency of the pulsed high-frequency power and the duty ratio of the first level and the second level of the pulsed high-frequency power (hereinafter referred to as the pulse duty ratio) through input from an input device (not shown) for input by a user or automatic input based on a preset program. For example, as the pulse frequency, a ratio of the high-frequency voltage v a 、v b A predetermined frequency (e.g., 10 kHz) with a low frequency (long period) is set to, for example, 50% as a pulse duty ratio. The control unit 9 generates an output control signal of a pulse waveform for instructing pulsed high-frequency power based on the pulse frequency and the pulse duty ratio. Furthermore, the control unit 9 switches the phase difference θ to the first phase difference θ1 during the high level period of the output control signal and to the second phase difference θ2 during the low level period.

[0116] Since the phase difference θ becomes the first phase difference θ1 during the high level period of the output control signal, the high frequency voltage v outputted from the high frequency signal generating unit 8 is a 、v b The phase difference θ becomes the first phase difference θ1, and the high frequency voltage v output from the first DC-RF converter 4A is PA The high frequency voltage v output from the second DC-RF converter 4B PB The phase difference θ is also called the first phase difference θ1. The output power P synthesized corresponding to the first phase difference θ1 XThe output is output from the RF synthesizer 5. In this embodiment, since the first phase difference θ1 is set to 20 [deg], the output power P during the high level period X , becomes the power P to be output from the first DC-RF converter 4A A The power P output from the second DC-RF converter 4B B Added power P in About 95% (electricity P in About 5% of the total energy is consumed by the RF synthesis section 5).

[0117] In addition, since the phase difference θ becomes the second phase difference θ2 during the low level period of the output control signal, the high frequency voltage v output from the high frequency signal generating unit 8 is a 、v b The phase difference θ becomes the second phase difference θ2, and the high frequency voltage v output from the first DC-RF converter 4A is PA The high frequency voltage v output from the second DC-RF converter 4B PB The phase difference θ is also the second phase difference θ2. And the output power P synthesized corresponding to the second phase difference θ2 X It is output from the RF synthesizer 5. In this embodiment, since the second phase difference θ2 is set to 160 [deg], the output power P during the low level period is X Become a Power P in About 5% (electricity P in About 95% of the energy is consumed by the RF synthesis section 5).

[0118] Thus, the output power P outputted from the RF synthesizer 5 is X Become a power P in During the high level period of about 95%, and the power P in The pulse-shaped high-frequency power during the low level period of about 5%.

[0119] Fig. 9 is the high frequency voltage v output from the RF synthesizer 5 PX The waveform of the high frequency voltage v PX When the phase difference θ is the first phase difference θ1, it becomes a high level with a large amplitude, and when the phase difference θ is the second phase difference θ2, it becomes a low level with a small amplitude. X It becomes pulsed high-frequency electricity.

[0120] In addition, the control unit 9 controls the high frequency power (traveling wave power P) output from the high frequency power source 1 to the load. f ) control is a feedback control of the control target. As the control target, the target output power P during the high level period is set fs1and the target output power P during the low level period fs2 The user operates an input device (not shown) to manually input the target output power P fs1 and P fs2 , or automatically input the target output power P through a pre-set program fs1 and P fs2 .

[0121] The control unit 9 calculates the traveling wave power P input from the power detection unit 10 during the high level period of the output control signal. f The detected value and the target output power P fs1 The deviation ΔP1(=P fs1 -P f ), and based on the deviation ΔP1, a control command value for making the deviation ΔP1 zero is generated. Then, the control unit 9 changes the first phase difference θ1 based on the control command value, thereby controlling the traveling wave power P f Therefore, feedback control is performed so that the traveling wave power P f The target output power P fs1 In addition, the control unit 9 calculates the traveling wave power P input from the power detection unit 10 during the low level period of the output control signal. f The detected value and target output power P fs2 The deviation ΔP2 (=P fs2 -P f ), and generates a control command value for making the deviation ΔP2 zero based on the deviation ΔP2. Then, the control unit 9 changes the second phase difference θ2 based on the control command value to control the traveling wave power P f Therefore, feedback control is performed so that the traveling wave power P f The target output power P fs2 .

[0122] In addition, the traveling wave power P may be controlled by changing the first phase difference θ1 and the second phase difference θ2 instead of changing the first phase difference θ1 and the second phase difference θ2. f , but the DC voltage V output by the DC-DC converter 3 dc Change to control the traveling wave power P f At this time, the control unit 9 outputs the generated control command value to the PWM signal generating unit 7, and the PWM signal generating unit 7 generates a PWM signal S by using a triangular wave comparison method according to the control command value and the generated carrier signal. PWM In addition, the control unit 9 may change the amplitude A output to the high-frequency signal generating unit 8 based on the control command value, thereby performing output power control.

[0123] As described above, according to the high frequency power supply 1 of this 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 of the first and second DC-RF converters 4A and 4B is converted into A , P B The synthesized RF synthesizer 5 converts the high frequency voltage v input to the first and second DC-RF converters 4A and 4B. a 、v b The phase difference θ is switched between the first phase difference θ1 and the second phase difference θ2. As a result, the output power P outputted from the RF synthesizer 5 is X When the phase difference θ is the first phase difference θ1, the power P in When the phase difference θ is the second phase difference θ2, the power P in The phase difference θ can be switched at high speed, so that the pulsed high frequency power with increased pulse frequency of switching between the first level and the second level can be output.

[0124] In addition, according to the high frequency power supply 1 of this embodiment, the DC voltage V output by the DC-DC converter 3 is dc Maintain a constant (target output power P fs1 is constant), it is possible to output pulsed high-frequency power. dc Overshoot and undershoot caused by the change will not occur.

[0125] In addition, in this embodiment, the traveling wave power P f The control target is 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 f -Reflected wave power P r ) control as the control target.

[0126] According to the above embodiment, a first DC-RF converter 4A and a second DC-RF converter 4B having the same structure are provided as the DC-RF converter 4, and the output power P of the two DC-RF converters 4A and 4B is converted into A , P B Although the RF synthesizer 5 performs synthesis, three or more DC-RF converters may be provided to synthesize the output power of each DC-RF converter.

[0127] Fig.10 , Fig.11This is a diagram showing the circuit configuration of a DC-RF converter 4' and an RF synthesizer 5' in a case where three DC-RF converters of the same configuration are provided in a 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'.

[0128] Fig.10 , Fig.11 The circuit structure can be regarded as Figure 1 The DC-RF converter 4 and RF synthesizer 5 shown in the figure are additionally provided with a third DC-RF converter 4C and a second RF synthesizer 5B, 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.

[0129] In the case of providing three DC-RF converters of the same structure, the first method is to set the output voltage v of the first and second DC-RF converters 4A and 4B in the DC-RF converter 4' to PA 、v PB The output voltage v of the third DC-RF converter 4C is driven with a phase difference θ=0. PC Relative to the output voltage v PA 、v PB The second method is to control the output voltage v of the second DC-RF converter 4B by setting the phase difference θ to drive; PB With respect to the output voltage v of the first DC-RF converter 4A PA The phase difference θ is set to drive, and the output voltage v of the third DC-RF conversion unit 4C is PC With respect to the output voltage v of the first RF synthesizer 5A PX The driving mode is controlled by setting the phase difference ψ.

[0130] Fig.10 1 is a circuit configuration of a DC-RF converter 4' and an RF synthesizer 5' showing the first method. Fig.11 This is a circuit configuration of a DC-RF converter 4' and an RF synthesizer 5' showing the case of the second method.

[0131] exist Fig.10 In the first method shown in FIG. 1 , the first and second DC-RF converters 4A and 4B and the first RF synthesizer 5A can be replaced by an equivalent DC-RF converter, so the high-frequency generator U′ is the same as the high-frequency generator U (see FIG. 1 ). Figure 1) are substantially the same. That is, the first RF synthesizer 5A performs the function of converting the output power P of the first DC-RF converter 4A into A and the output power P of the second DC-RF converter 4B B The second RF synthesizer 5B maintains the function of synthesizing as it is, and adjusts the output power P to the load according to the phase difference θ. Z function.

[0132] When the high frequency signal v input to the first, second, and third DC-RF converters 4A, 4B, and 4C is 1 、v 2 、v 3 The waveform is v 1 =A 1 ·sin(ω·t+φ 1 ),v 2 =A 2 ·sin(ω·t+φ 2 ),v 3 =A 3 ·sin(ω·t+φ 3 ) Fig.10 In the first method shown in the figure, the first and second DC-RF converters 4A and 4B are input with, for example, v a =A·sin(ω·t)(A 1 =A 2 =A、φ 1 =φ 2 =0) high frequency signal.

[0133] When the input port and output port of the RF synthesizer 5A, 5B are matched, the output voltage v of the first and second DC-RF converters 4A, 4B is PA 、v PB By v PA =v PB =V·sin(ω·t) represents the output voltage v of the first RF synthesizer 5A. PX From (8) v PX =V·sin(ω·t). Therefore, the third DC-RF converter 4C inputs v b =A·sin(ω·t+θ)(A 3 =A、φ 3 =θ), and the third DC-RF converter 4C outputs a high-frequency signal v PC =V·sin(ω·t+θ), the second RF synthesizer 5B outputs v PZ =V·cos(θ / 2)·sin(ω·t+θ / 2) output voltage v PZ .

[0134] Since the output power P of the first and second DC-RF converters 4A and 4B A , P B Since the first RF synthesizer 5A does not consume the heat, the first RF synthesizer 5A outputs (P A +P B ) of electric power P X In the second RF synthesis unit 5B, the output power P X and the output power P of the third DC-RF converter 4C C The synthesis formula represented by formula (9) is synthesized, and the output is P Z =2·[V·cos(θ / 2)] 2 ·sin 2 (ω·t+θ / 2) / R o The power P Z .

[0135] Therefore, in Fig.10 In the first method shown in the figure, 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 θ1 and the second phase difference θ2. A , P B Total power P X =(P A +P B ) and the output power P of the third DC-RF converter 4C C The resultant amount of power P Z Output as pulsed high-frequency power.

[0136] On the other hand, Fig.11 In the second method shown in the figure, the output power P to the load is adjusted by both the first RF synthesizer 5A and the second RF synthesizer 5B. Z Input v to the first and second DC-RF converters 4A and 4B respectively. a =A·sin(ω·t)(φ 1 =0) and v b =A·sin(ω·t+θ)(φ 2 =θ), the first and second DC-RF converters 4A and 4B respectively output an output voltage v PA =V·sin(ω·t),v PB =V·sin(ω·t+θ), the output voltage v of the first RF synthesizer 5A PX From (8) v PX =V·cos(θ / 2)·sin(ω·t+θ / 2).

[0137] The amplitude A is adjusted according to the phase difference θ when input to the third DC-RF converter 4C. 3 and φ 3 V c =A·cos(θ / 2)·sin(ω·t+θ / 2+ψ)(A 3 =A·cos(θ / 2),φ 3 =θ / 2+ψ), and the output voltage v of V·cos(θ / 2)·sin(ω·t+θ / 2+ψ) is output from the third DC-RF converter 4C. PC The second RF synthesizer 5B outputs the signal generated by v PZ =V·cos(θ / 2)·cos(ψ / 2)·sin(ω·t+θ / 2+ψ / 2) Output voltage v PZ , and the output is P Z =2·[V·cos(θ / 2)·cos(ψ / 2)] 2 ·sin 2 (ω·t+θ / 2+ψ / 2) / R o The output power P Z .

[0138] Therefore, in Fig.11 In the second method shown in FIG. 1 , whether the phase difference θ is switched between the first phase difference θ1 and the second phase difference θ2 by fixing the phase difference ψ, or vice versa, the phase difference ψ is switched between ψ1 and ψ2 by fixing the phase difference θ, the power P can be made Z That is, the output power P of the first DC-RF converter 4A is switched by switching the phase difference θ between the first phase difference θ1 and the second phase difference θ2. A and the output power P of the second DC-RF converter 4B B The combined amount of power P Z The output power P of the first and second DC-RF converters 4A and 4B is switched by switching the phase difference ψ between ψ1 and ψ2. A , P B The synthetic power P X and the output power P of the third DC-RF converter 4C C The synthetic amount can make the power P Z Output as pulsed high-frequency power.

[0139] Fig.12 , Fig.13This is a diagram showing the circuit configuration of a DC-RF converter 4" and an RF synthesizer 5" in a case where four DC-RF converters of the same configuration are provided in a high-frequency generating section 1". In the DC-RF converter 4", a third DC-RF converter 4C and a fourth DC-RF converter 4D having the same configuration as the first and second DC-RF converters 4A and 4B are added, and in the RF synthesizer 5", a first RF synthesizer 5A, a second RF synthesizer 5B and a third RF synthesizer 5C having the same configuration as the RF synthesizer 5 are provided.

[0140] 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". A and the output power P of the second DC-RF converter 4B B The second RF synthesizer 5B synthesizes the output power P of the third DC-RF converter 4C in the DC-RF converter 4". C and the output power P of the fourth DC-RF converter 4D D In addition, the third RF synthesizer 5C in the RF synthesizer 5" synthesizes the output power P of the first RF synthesizer 5A. X and the output power P of the second RF synthesizer 5B Y .

[0141] Even when four DC-RF converters of the same structure are provided, two methods are considered. The first method is as follows: PA The output voltage v of the second DC-RF converter 4B PB The phase difference θ is set between them, and the output voltage v of the third DC-RF conversion unit 4C is PC The output voltage v of the fourth DC-RF converter 4D PD In the first method, it is equivalent to setting a phase difference θ between Figure 1 The DC-RF converter 4 and the RF synthesizer 5 are provided in two pieces, and two electric powers output from the two pieces are synthesized by a third RF synthesizer 5C.

[0142] Fig.12 FIG. 4 shows the circuit configuration of the DC-RF converter 4" and the RF synthesizer 5" in the case of the first method. The high-frequency signal v input to the first to fourth DC-RF converters 4A, 4B, 4C, 4D 1 、v 2 、v 3 、v 4 The waveform is set to v 1 =A 1 ·sin(ω·t+φ 1 ),v2 =A 2 ·sin(ω·t+φ 2 ),v 3 =A 3 ·sin(ω·t+φ 3 ),v 4 =A 4 ·sin(ω·t+φ 4 ) Fig.12 In the first method shown, v becomes: 1 =v a =A·sin(ω·t)(A 1 =A,φ 1 =0), v 2 =v b =A·sin(ω·t+θ)(A 2 =A,φ 2 =θ), v 3 =v a =A·sin(ω·t)(A 3 =A,φ 3 =0), v 4 =v b =A·sin(ω·t+θ)(A 4 =A,φ 4 =θ).

[0143] Fig.12 In the circuit configuration shown in FIG. 1 , the output power P of the first DC-RF converter 4A is converted by the first RF synthesizer 5A based on the phase difference θ. A and the output power P of the second DC-RF converter 4B B The output power P of the third DC-RF converter 4C is synthesized at a predetermined ratio by the second RF synthesizer 5B based on the phase difference θ. C and the output power P of the fourth DC-RF converter 4D D Synthesize according to the specified ratio.

[0144] When the input ports of the RF synthesizers 5A, 5B, and 5C are matched, the output power P of the first RF synthesizer 5A is X and the output power P of the second RF synthesizer 5B Y From (9) P X =P Y =2·V 2 ·cos 2 (θ / 2)·sin 2 (ω·t+θ / 2) / R o In addition, the third RF synthesizer 5C outputs the power P X And output power P YThe third RF synthesizer 5C outputs P to the load without being consumed by heat. Z =P X +P Y =4·V 2 ·cos 2 (θ / 2)·sin 2 (ω·t+θ / 2) / R o Output power P Z .

[0145] Therefore, in Fig.12 In the first method shown in the figure, the output power P of the first DC-RF converter 4A is switched by switching the phase difference θ between the first phase difference θ1 and the second phase difference θ2. A and the output power P of the second DC-RF converter 4B B The resultant amount of power P X As a pulsed high frequency power output, the output power P of the third DC-RF converter 4C is switched. C and the output power P of the fourth DC-RF converter 4D D The resultant amount of power P Y The high-frequency power is output as a pulse. X and power P Y The third RF synthesizer 5C synthesizes the power P Z It also becomes pulsed high-frequency electricity.

[0146] The second method is to control the output voltage v of the first DC-RF conversion unit 4A with the same phase. PA and the output voltage v of the second DC-RF conversion unit 4B PB , and controls the output voltage v of the third DC-RF conversion unit 4C with the same phase PC and the output voltage v of the fourth DC-RF converter 4D PD , the output voltage v of the first RF synthesis unit 5A PX The output voltage v of the second RF synthesizer 5B PY The phase difference θ is set between them.

[0147] Fig.13 4 is a circuit structure of a DC-RF converter 4" and an RF synthesizer 5" in the case of the second method. Fig.13 In the circuit structure shown in the figure, the output power P of the first DC-RF converter 4A is converted by the first RF synthesizer 5A. A and the output power P of the second DC-RF converter 4B B The output power P of the third DC-RF converter 4C is synthesized by the second RF synthesizer 5B.C and the output power P of the fourth DC-RF converter 4D D The output power P of the first RF synthesizer 5A is synthesized as it is. Then, the third RF synthesizer 5C synthesizes the output power P of the first RF synthesizer 5A based on the phase difference θ. X and the output power P of the second RF synthesizer 5B Y Synthesize according to the specified ratio.

[0148] For example, the high frequency signal v input to the first and second DC-RF converters 4A and 4B is 1 、v 2 The waveform is set to v 1 =v 2 =v a =A·sin(ω·t)(A 1 =A 2 =A,φ 1 =φ 2 =0), the output voltage v of the first RF synthesizer 5A PX From (8) v PX =V·sin(ω·t). In addition, the high-frequency signal v input to the third and fourth DC-RF converters 4C and 4D is 3 、v 4 The waveform is set to v 3 =v 4 =v b =A·sin(ω·t+θ)(A 3 =A 4 =A,φ 3 =φ 4 =θ), the output voltage v of the second RF synthesizer 5B PY From (8) v PY =V·sin(ω·t+θ).

[0149] Therefore, the third RF synthesizer 5C outputs v according to equation (8): PZ =V·cos(θ / 2)·sin(ω·t+θ / 2)] This output voltage v PZ According to formula (9), the load output P Z =2·[V·cos(θ / 2)] 2 ·sin 2 (ω·t+θ / 2) / R o This output power v PZ .

[0150] Therefore, in Fig.13 In the second method shown in the figure, the output power P of the first RF synthesizer 5A is switched by switching the phase difference θ between the first phase difference θ1 and the second phase difference θ2. X (=PA +P B ) and the output power P of the second RF synthesizer 5B Y (=P C +P D ) can make the power P Z Output as pulsed high-frequency power.

[0151] exist Figure 1 In the embodiment shown, the output voltage v of the first DC-RF conversion unit 4A is PA The initial phase φ a The output voltage v of the second DC-RF converter 4B is fixed. PB The initial phase φ b changes, so that the phase difference θ = φ b -φ a changes, but it can also be achieved by changing the initial phase φ b Fixed, so that the initial phase φ a changes, so that the phase difference θ = φ b -φ a Alternatively, the initial phase φ a ,φ b The two change, and the phase difference θ = φ b -φ a change.

[0152] In the above embodiment, the RF synthesizer 5 is described as a circuit structure for synthesizing two RF powers, but the RF synthesizer 5 may be a circuit for synthesizing three or more RF powers. As a circuit for synthesizing three or more RF powers, for example, Fig.14 The circuit shown.

[0153] For example, using Fig.14 When the power combining circuit of (b) combines three RF powers, the input voltage v input to the input terminals 1, 2, and 3 is a 、v b 、v c Set to v a =A·sin(ω·t+φ a ),v b =B·sin(ω·t+φ b ),v c =C·sin(ω·t+φc), the effective value is set to v arms 、v brms 、v crms When the input power P is input into the power synthesis circuit a =v arms 2 / R、P b=v brms 2 / R、P c =v crms 2 / R. If not v a =v b =v c , the three resistors R in the circuit generate a differential voltage v ab =v a -v b 、v bc =v b -v c 、v ca =v c -v a , so the difference voltage v ab 、v bc 、v ca The effective value is set to v abrms 、v bcrms 、v carms When the three resistors R respectively consume heat P ab =v abrms 2 / R、P bc =v bcrms 2 / R、P ca =v carms 2 / R's electricity.

[0154] Therefore, by inputting the voltage v a 、v b 、v c Set the phase difference θ between each other ab ,θ bc ,θ ca , the power synthesis circuit can convert the input power P in =P a +P b +P c A portion of the electricity (P ab +P bc +P ca ) heat consumption, and the remaining electricity P in -(P ab +P bc +P ca ) is output to the load. The same is true when 4 or more RF powers are input.

[0155] In the above embodiment, the output control of the high frequency power supply 1 is explained by taking a plasma processing system in which the high frequency power supply 1 is connected as a load to a plasma processing device as an example. Fig.15As shown, the present invention can also be applied to a case where an impedance matching device 12 is provided between the high frequency power source 1 and the plasma processing device 11 .

[0156] When an impedance matching device 12 is provided, even if the impedance (load impedance) of the plasma processing device 8 changes, impedance matching between the high-frequency power supply 1 and the plasma processing device 12 can be performed by the impedance matching device 12. However, since the impedance matching device 12 is in an unmatched state during the transition period of the impedance matching process, the output control method of the high-frequency power supply 1 of the present invention is also effective in a plasma processing system having the impedance matching device 12.

[0157] The main purpose of the above-mentioned embodiment is that a high-frequency generating unit U that synthesizes multiple high-frequency powers outputs, for example, a pulsed high-frequency power having a high-level period and a low-level period by switching the phase difference θ between a first phase difference θ1 and a second phase difference θ2. Therefore, it is not limited to a high-frequency power supply for a plasma processing system.

[0158] In the above embodiment, the high frequency voltage v output to the load out The waveform is a sine wave, but it can also be a trapezoidal wave or a rectangular wave with dead time.

[0159] In the above embodiment, the control unit 9 switches the phase difference θ output to the high-frequency signal generating unit 8 between two values ​​θ1 and θ2, thereby outputting a pulsed high-frequency power in which the amplitude of the high-frequency power is switched between the first level and the second level, but the present invention is not limited to this. For example, the amplitude of the high-frequency power may be switched between three or more levels.

[0160] Fig.16 (a) shows the high frequency voltage v output from the RF synthesizer 5. PX The control unit 9 switches the phase difference θ output to the high-frequency signal generating unit 8 between three values: a first phase difference θ1 (e.g., 20 [deg]), a second phase difference θ2 (e.g., 90 [deg]), and a third phase difference θ3 (e.g., 160 [deg]), so that the high-frequency voltage v output from the RF synthesizing unit 5 is PX The waveform is Fig.16 The waveform shown in (a) changes in three levels. Therefore, the high frequency power P output from the RF synthesizer 5 X The amplitude is switched among 3 levels.

[0161] In addition, the phase difference θ does not need to be switched between a plurality of fixed values, but may be a value of a predetermined function that changes according to time t.

[0162] For example, if the phase difference θ is a linear function of time t, θ=a·t+b (a and b are constants), the synthesis ratio η(θ) in the RF synthesis unit 5 is Figure 5 The characteristic (a) shown in FIG. 1 is that the high frequency voltage v output from the RF synthesizer 5 is PX The waveform is as Fig.16 (b) changes to a sine wave. Therefore, the high frequency power P output from the RF synthesizer 5 X Changes to a sine wave.

[0163] In addition, when it is desired to make the high frequency power P X When the high frequency voltage v PX The phase difference θ can be changed so that the waveform becomes the desired waveform shape. That is, as mentioned above, since the synthesis ratio η(θ) is (cos 2 (θ / 2)), the phase difference θ at the desired synthesis ratio η can be expressed by the following formula (11).

[0164]

[0165] Therefore, for example, the high frequency voltage v PX The waveform becomes Fig.16 In the case of the waveform (triangular waveform) shown in (c), the Fig.16 The phase difference θ can be changed according to the time t in the manner of the synthesis ratio η corresponding to the waveform shown in (c). That is, in the above formula (11), the synthesis ratio η is expressed as Fig.16 (c) The function x(t) of the waveform shown in FIG. If this concept is applied, the synthesis ratio η can be freely set. For example, Fig.16 By combining a triangular wave with a constant level waveform as shown in (d), it is also possible to Fig.16 As shown in (e), a sine wave waveform and a waveform of a certain level are combined.

[0166] In addition, Fig.16 In (b) to (e), the synthesis ratio η(θ) in the RF synthesis unit 5 may become zero, and the output may become zero. If you do not want the output to become zero, you can adjust the calculation formula of the phase difference θ so that the phase difference θ does not become 180 [deg].

[0167] In addition, the high frequency voltage v PX The waveform is formed as Fig. 9 In the waveform shown, an overshoot waveform is provided when the plasma is ignited (refer to Fig.16(f)). In order to form such a waveform, in a waveform in which the phase difference θ is repeatedly set to the first phase difference θ1 (for example, 20 [deg]) during the first period t1 and the phase difference θ is repeatedly set to the second phase difference θ2 (for example, 160 [deg]), when the plasma is ignited, a third period t3 is set to set an overshoot before the first period t1, and in the third period t3, the phase difference θ is formed, for example, as shown in the following formula (12). In addition, T is the length of the third period t3. Thus, it can be formed that: when the plasma is ignited (at the beginning of the third period t3: t=0), the phase difference θ=0, and the composite ratio η is the largest. During the third period t3, the phase difference θ increases and the composite ratio η decreases. At the end of the third period t3 (t=T), the phase difference becomes θ=θ1. In addition, during the third period t3, the phase difference θ can also be set to "0". By making the high-frequency voltage v PX The waveform is formed to include Fig.16 (f) shows the overshoot waveform, when the plasma is not ignited, the high-frequency voltage v output to the load out becomes higher, so the ignition property of plasma can be improved.

[0168] θ=(θ1 / T)·t…(12)

[0169] Fig.16 The waveforms and the calculation formula (12) are examples. By appropriately setting the phase difference θ, the high-frequency voltage v output from the RF synthesizer 5 can be made PX The waveform of the high frequency power P output from the RF synthesizer 5 can be changed into various waveforms. X The waveform becomes the desired waveform.

[0170] The high frequency power supply of the present invention is not limited to the above-mentioned embodiment. The specific structure of each part of the high frequency power supply of the present invention can be freely changed in various designs.

[0171] Description of Reference Numerals

[0172] 1 High frequency power supply

[0173] 2 AC-DC conversion unit

[0174] 3 DC-DC conversion unit

[0175] 4, 4', 4" DC-RF conversion unit (high frequency generation unit)

[0176] 4A First DC-RF conversion unit (high frequency generation unit)

[0177] 4B Second DC-RF conversion unit (high frequency generation unit)

[0178] 4C Third DC-RF conversion unit (high frequency generation unit)

[0179] 4D Fourth DC-RF conversion unit (high frequency generation unit)

[0180] 401 Low-pass filter

[0181] 5, 5', 5" RF synthesis section (high frequency synthesis unit)

[0182] 5A 1st RF synthesis section (high frequency synthesis unit)

[0183] 5B Second RF synthesis section (high frequency synthesis unit)

[0184] 5C The third RF synthesis unit (high frequency synthesis unit)

[0185] 6 Filter circuit

[0186] 7 PWM signal generation unit

[0187] 8 High frequency signal generation unit (high frequency generation unit)

[0188] 8a The first high frequency generating circuit

[0189] 8b Second high frequency generating circuit

[0190] 9 Control unit (output control unit)

[0191] 10 Power detection unit

[0192] 11 Plasma treatment device

[0193] 12 Impedance matching device

[0194] U, U', U” high frequency generating section.

Claims

1. A high frequency power supply, characterized in that: include: A plurality of high-frequency signal generating units that output high-frequency signals whose phase differences can be changed; a high frequency generating unit including a plurality of DC-RF converters for amplifying the high frequency signal generated by the high frequency signal generating unit with a direct current voltage and outputting the amplified high frequency signal 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 conversion units constituting the plurality of DC-RF conversion units; a high frequency synthesizing unit that synthesizes a plurality of high frequencies output from the plurality of DC-RF conversion units at a predetermined ratio based on the phase difference and outputs the synthesized high frequencies to a load; and an output control unit that controls the high-frequency power output from the high-frequency synthesis unit by changing the phase difference between the high-frequency voltages output from the DC-RF conversion units corresponding to the high-frequency signal generation units by giving information including information about the phase difference to each high-frequency signal generation unit constituting the plurality of high-frequency signal generation units, wherein The voltage supply unit supplies a direct current voltage having a voltage value greater than 0 to each of the DC-RF converters to maintain a state in which each of the DC-RF converters constituting the plurality of DC-RF converters generates a high frequency voltage. The plurality of high-frequency signal generating units output the high-frequency signal to maintain the state where the DC-RF converters generate the high-frequency voltage during the period when the DC voltage having a voltage value greater than 0 is supplied to the DC-RF converters, thereby outputting the high-frequency voltage from the plurality of DC-RF converters. The output control unit is capable of executing (a) a certain control in which the phase difference between the plurality of DC-RF converters is not changed so that the power value of the high-frequency power output by the high-frequency synthesis unit becomes a certain value; (b) an increase control in which the phase difference between the plurality of DC-RF converters is changed so that the power value of the high-frequency power output by the high-frequency synthesis unit increases; and (c) a decrease control in which the phase difference between the plurality of DC-RF converters is changed so that the power value of the high-frequency power output by the high-frequency synthesis unit decreases, and by arbitrarily combining the respective controls, the power value of the high-frequency power output from the high-frequency synthesis unit becomes a desired power value greater than 0. Each of the DC-RF converters constituting the plurality of DC-RF converters receives as input a high-frequency signal output from only any one of the high-frequency signal generating units constituting the plurality of high-frequency signal generating units, The output control unit switches the phase difference between a first prescribed value, a second prescribed value, and a third prescribed value, When starting output to the load, the output control unit makes the output when the phase difference is the third predetermined value larger than the output when the phase difference is the first predetermined value and the second predetermined value, so that the waveform of the high-frequency voltage includes an overshoot waveform.

2. The high frequency power supply according to claim 1, characterized in that: The predetermined ratio when the phase difference is the first predetermined value is greater than the predetermined ratio when the phase difference is the second predetermined value.

3. The high frequency power supply according to claim 2, characterized in that: The first predetermined value is greater than or equal to 0[deg] and less than 90[deg], The second predetermined value is greater than or equal to 90 [deg] and less than or equal to 180 [deg].

4. The high frequency power supply according to claim 3, characterized in that: The first prescribed value is 0 [deg].

5. The high frequency power supply according to claim 3, characterized in that: The second predetermined value is 180 [deg].

6. The high frequency power supply according to claim 2 or 3, characterized in that: The output control means performs feedback control of the high-frequency power by changing the first predetermined value or the second predetermined value.

7. The high frequency power supply according to any one of claims 2 to 4, characterized in that: The high frequency generating unit generates a first high frequency and a second high frequency, The output control unit switches a phase difference of the second high frequency with respect to the first high frequency between the first predetermined value and the second predetermined value.

8. The high frequency power supply according to claim 1, characterized in that: The output control unit changes the phase difference according to a linear function.

9. The high frequency power supply according to claim 1, characterized in that: The output control unit changes the phase difference according to the following formula: θ=2·cos -1 (√x(t)) Here, θ is the phase difference, and x(t) is a function representing the desired waveform.

10. The high frequency power supply according to claim 1, characterized in that: The output control unit switches the phase difference between a first predetermined value and a value of a predetermined function.

11. The high frequency power supply according to any one of claims 1 to 4 and 8 to 10, characterized in that: The output control unit makes the prescribed ratio not equal to zero.

12. The high frequency power supply according to any one of claims 1 to 4 and 8 to 10, characterized in that: The high frequency synthesizing unit is composed of a hybrid circuit including a transmission transformer and a resistor for power consumption. 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.

Images