WO2008050619A1

WO2008050619A1 - Power supply and microwave generator using same

Info

Publication number: WO2008050619A1
Application number: PCT/JP2007/069953
Authority: WO
Inventors: Shigeru Kasai; Yuki Osada; Yuji Obata
Original assignee: Tokyo Electron Limited
Priority date: 2006-10-27
Filing date: 2007-10-12
Publication date: 2008-05-02
Also published as: JP5171010B2; TWI418259B; JP2008113473A; CN101529710A; KR20090055630A; KR101170591B1; CN101529710B; TW200830946A

Abstract

A power supply comprises an AC/DC converting section for converting AC voltage into DC voltage, a switching circuit having switching elements and outputting a pulse voltage according to the combination of ons and offs of the switching elements due to an on/off cycle of each switching element caused when the DC voltage is inputted and a control section for performing phase-shift PWM control to control the pulse width of the pulse voltage outputted from the switching circuit by varying the phase of the on/off cycle of each switching element. The power supply is characterized in that the control circuit inserts a timing at which the switching elements are all off in the on/off cycles of the switching elements.

Description

Specification

Power supply device and microwave generator using the same

Technical field

TECHNICAL FIELD [0001] The present invention relates to a power supply device having a switching circuit that performs a switching operation by phase shift type PWM control, and a microwave generator using the power supply device

In the manufacturing process of a semiconductor device or a liquid crystal display device, a plasma processing such as an etching process or a film forming process is performed on a semiconductor wafer, a glass substrate, and a substrate to be processed. For this reason, a plasma processing apparatus such as a plasma etching apparatus or a plasma CVD film forming apparatus is used.

[0003] As a method of generating plasma in a plasma processing apparatus, a processing gas is supplied into a chamber in which parallel plate electrodes are arranged, a predetermined power is supplied to the parallel plate electrodes, and capacitive coupling between the parallel plate electrodes is performed. A method of generating plasma by using the method has been widely used. However, recently, a method using microwaves has been attracting attention as a plasma capable of realizing a high plasma density and a low electron temperature.

[0004] As a plasma source using a microwave, a plasma source using a microwave generator equipped with a magnetron is generally used. The magnetron is configured by coaxially arranging an anode (anode) having a cavity resonator around a filament as a cathode (force sword). With the DC electric field applied between these two electrodes, the cathode is heated and thermoelectrons are emitted. By adjusting the electric field (voltage) applied between both electrodes, the flowing current is controlled. At the same time, the thermoelectric element oscillates due to a rotational motion caused by a magnetic field applied in a direction perpendicular to the electric field. As a result, microwaves are generated.

[0005] When a magnetron is used for a microwave oscillator, a large-capacity high-voltage power supply is required. A switching circuit for a large-capacity DC power supply is usually composed of a full-bridge circuit using four transistors. In this case, the voltage applied to the transistor (FET) constituting the switching element can be reduced, and the voltage can be freely controlled by the number of transformer turns. The flow can be set.

[0006] Power control of a power supply using such a switching circuit is generally performed by PWM (Pulse Width Modulation) control. Conventionally, this control is performed by adjusting the ON / OFF time (duty cycle) of the transistor. However, if all the transistors are turned off for a long time, the load line potential becomes unstable and the switching loss increases.

[0007] As a technique for avoiding such inconvenience, phase shift type PWM control is known in which the ON time of each transistor is controlled by shifting the phase with the duty ratio of the gate signal of each transistor being constant. (For example, Transistor Technology, June 2004, pp. 228-235 (Non-Patent Document 1)). Resonance circuits can be easily formed by performing phase-shift PWM control, so the force S that allows efficient switching operation is reduced.

Summary of the Invention

[0008] When phase shift type PWM control using a full bridge circuit as described above is performed, MOS transistors with high switching efficiency are often used. However, when the off-time is long, that is, the duty ratio of the voltage signal output from the circuit and applied to the load is small! / Sometimes turned on! /, The parasitic capacitance between the source and drain of the transistor Not enough charge is accumulated in the part. For this reason, after turning this off, when another transistor connected in series to this transistor is turned on, a large inrush current flows to the on-state transistor through the capacitance portion of the transistor that was turned off. As a result, these transistors generate heat and cause a large loss.

[0009] On the other hand, when the duty ratio of the voltage signal applied to the load is large! /, Greater power is required. However, in normal phase shift control, the efficiency is reduced and sufficient power may not be obtained.

[0010] The present invention has been made in view of the power and the circumstances, and the switching circuit is operated by the phase shift type PWM control, while being less affected by loss such as heat generation and having high efficiency. It is an object to provide a power supply device and a microwave generator using the power supply device. [0011] It is another object of the present invention to provide a power supply device having both high efficiency and high power while operating the switching circuit by phase shift type PWM control, and a microwave generation device using the power supply device. And

[0012] It is another object of the present invention to provide a computer program for controlling the switching circuit of such a power supply device.

[0013] The present invention includes an AC / DC converter that converts an AC voltage into a DC voltage and a plurality of switching elements, and when a DC voltage is input, an on-off-site occurs in each of the switching elements. And a pulse output from the switching circuit by changing the phase of the on / off cycle of each switching element. And a control unit that performs phase shift PWM control for controlling the pulse width of the voltage, and the control unit is a timing at which all of the plurality of switching elements are turned off in the ON / OFF cycle of the switching element. This is a power supply device that is characterized by the fact that it is inserted.

[0014] According to the present invention, in the on / off cycle of the switching element, the timing at which all of the plurality of switching elements are turned off is inserted. Can be charged. Thereby, for example, in a switching transistor, it is possible to prevent the occurrence of an inrush current due to a small charge. For this reason, loss due to inrush current and heat generation of the transistor can be suppressed.

[0015] The present invention also includes an AC / DC converter that converts an AC voltage into a DC voltage, and a plurality of switching elements, and each switching element is turned on and off when a DC voltage is input. And a switching circuit that outputs a Norse voltage based on the on / off combination of each of the switching elements, and the switching circuit that is output by changing the phase of the on / off cycle of each of the switching elements. And a control unit that performs phase shift type PWM control for controlling the pulse width of the pulsed voltage, wherein the control unit is configured such that the duty ratio of the pulsed voltage output from the switching circuit is smaller than a predetermined value. In the ON / OFF cycle of the switching element, The timing at which all the plurality of switching elements are turned off is inserted. On the other hand, when the duty ratio is equal to or greater than the predetermined value, the timing at which all the plurality of switching elements are turned off is set. This is a power supply device that is designed not to be inserted.

According to the present invention, when the duty ratio of the pulse voltage output from the switching circuit is smaller than a predetermined value, the timing at which all the switching elements are turned off in the on / off cycle of the switching element. By inserting the voltage, for example, the parasitic capacitance of the switching transistor can be sufficiently charged during the operation. On the other hand, when the duty ratio is equal to or greater than the predetermined value, the timing at which all the plurality of switching elements are turned off is not inserted. As a result, the switch loss in the high duty ratio region is reduced, and more efficient control can be achieved.

[0017] The present invention also includes an AC / DC converter that converts an AC voltage into a DC voltage, and a plurality of switching elements, and each switching element is turned on and off when a DC voltage is input. And a switching circuit that outputs a Norse voltage based on the on / off combination of each of the switching elements, and the switching circuit that is output by changing the phase of the on / off cycle of each of the switching elements. And a control unit that performs phase shift type PWM control for controlling the pulse width of the pulsed voltage, wherein the control unit is configured such that the duty ratio of the pulsed voltage output from the switching circuit is smaller than a predetermined value. On the other hand, the frequency of the ON / OFF cycle of each switching element is relatively increased, while the duty cycle is If over ratio of the predetermined value or more, it is the power supply, characterized in that summer to relatively lower the frequency of the on 'off cycle.

According to the present invention, when the duty ratio of the pulsed voltage output from the switching circuit is smaller than a predetermined value, the frequency of the on / off cycle of each switching element is relatively increased, and the duty cycle When the ratio is greater than or equal to the predetermined value, the frequency of the on-off cycle is relatively lowered. As a result, good power control performance is achieved in the low power mode, and high power efficiency is obtained in the high power mode. [0019] In this case, when the duty ratio is equal to or greater than the predetermined value, the control unit controls the frequency of the on / off cycle to be lower if the duty ratio is larger. Also good. Further, even when the duty ratio is smaller than a predetermined value, the control unit performs control so that the frequency of the on / off cycle is lower! / If the duty ratio is larger. It ’s going to be.

[0020] The present invention also includes an AC / DC converter that converts an AC voltage into a DC voltage, and a plurality of switching elements. When a DC voltage is input, each switching element is turned on and off. And a switching circuit that outputs a Norse voltage based on the on / off combination of each of the switching elements, and the switching circuit that is output by changing the phase of the on / off cycle of each of the switching elements. And a control unit that performs phase shift type PWM control for controlling the pulse width of the pulsed voltage, wherein the control unit is configured such that the duty ratio of the pulsed voltage output from the switching circuit is smaller than a predetermined value. In addition, in the ON / OFF cycle of the switching element, the timing at which all the plurality of switching elements are turned off is set. On the other hand, when the duty ratio is equal to or greater than the predetermined value, the timing at which all of the plurality of switching elements are turned off is not inserted, and the on / off cycle is not performed. The power supply apparatus is characterized in that the frequency is made lower than the frequency when the duty ratio is smaller than the predetermined value! /.

[0021] According to the present invention, finer control can be performed, and both efficiency and power controllability can be achieved at a high V level.

In this case, when the duty ratio is equal to or greater than the predetermined value, the control unit performs control so that the frequency of the on / off cycle is lower if the duty ratio is larger. Also good. Further, even when the duty ratio is smaller than a predetermined value, the control unit performs control so that the frequency of the on / off cycle is lower! / If the duty ratio is larger. It ’s going to be.

[0023] Further, the present invention includes an AC / DC converter that converts an AC voltage into a DC voltage, and a plurality of switching elements, and each switching element is turned on and off when a DC voltage is input. Based on the on / off combination of each of these switching elements. And a phase shift PWM control for controlling the pulse width of the pulse voltage output from the switching circuit by changing the phase of the ON / OFF cycle of each switching element. A control unit that performs the switching element in the ON / OFF cycle when the duty ratio of the pulse voltage output from the switching circuit is smaller than a first value. When the switching element is turned off, the duty ratio is smaller than a second value greater than the first value and greater than the first value! / In addition, the timing at which all of the plurality of switching elements are turned off is not inserted, and the duty ratio is A power supply device characterized in that, when the value is equal to or greater than 2, the frequency of the on / off cycle is made lower than the frequency when the duty ratio is smaller than the second value. .

[0024] According to the present invention, finer control can be performed, and both efficiency and power controllability can be achieved at a high V level.

[0025] In this case, when the duty ratio is greater than or equal to the second value, the control unit performs control so that the frequency of the on / off cycle is lower when the duty ratio is larger. It may be. Further, the control unit is configured such that, even when the duty ratio is greater than or equal to the first value and smaller than the second value, the frequency of the on / off cycle is lower when the duty ratio is larger. It may be controlled so that Further, the control unit may reduce the frequency of the ON / OFF cycle if the duty ratio is larger even when the duty ratio is smaller than the first value! To control! /, Even! /

[0026] In each of the above inventions, preferably, the switching circuit has four switching elements, which constitute a full bridge circuit. Preferably, the duty ratios of the on / off cycles of the four switching elements are the same.

For example, the switching element is a MOS FET or an IGBT. In addition, a step-up transformer that boosts the voltage output from the switching circuit may be further provided.

[0028] Further, the present invention provides a power supply device having any one of the above characteristics and the power supply device. A microwave oscillating device comprising: a microwave oscillating unit that feeds power and oscillates microwaves.

[0029] Preferably, the microwave oscillating unit includes a chamber in which the inside is maintained in a vacuum, a filament that is disposed in the chamber and functions as a cathode that emits thermoelectrons, and the filament in the chamber And a magnetron having an anode that is fed from the power supply device and that forms an electric field with the filament, and a magnetic field generation unit that forms a magnetic field orthogonal to the electric field outside the chamber. Is provided.

[0030] Further, the present invention includes an AC / DC converter that converts an AC voltage into a DC voltage, and a plurality of switching elements, and when each DC element is input, an on-off cycle is provided for each of the switching elements. And a switching circuit that outputs a Norse voltage based on a combination of ON and OFF of each of these switching elements, and a computer program for causing a computer to function to control a power supply device, A function of performing phase shift type PWM control for controlling a pulse width of a pulsed voltage output from the switching circuit by changing a phase of an on / off cycle of the switching element, and an on / off cycle of the switching element, And a function of inserting a timing when all of the plurality of switching elements are turned off. A computer program, characterized in that to realize the data.

[0031] Further, the present invention includes an AC / DC converter that converts an AC voltage into a DC voltage, and a plurality of switching elements, and each switching element is turned on and off when a DC voltage is input. And a switching circuit that outputs a Norse voltage based on a combination of ON and OFF of each of these switching elements, and a computer program for causing a computer to function to control a power supply device, A function of performing phase shift type PWM control for controlling the pulse width of the pulsed voltage output from the switching circuit by changing the phase of the ON / OFF cycle of the switching element; and the pulsed voltage output from the switching circuit ON / OFF cycle of the switching element when the duty ratio of the switching element is smaller than a predetermined value. Oite While the plurality of sweep rate Tsuchingu element is 揷入 the timing at which all off, when the duty ratio is equal to or higher than previous SL predetermined value, the timing at which the plurality of switching elements are all turned off This is a computer program characterized by having a computer realize the function of not inserting

[0032] Further, the present invention includes an AC / DC converter that converts an AC voltage into a DC voltage, and a plurality of switching elements, and each switching element is turned on and off when a DC voltage is input. And a switching circuit that outputs a Norse voltage based on a combination of ON and OFF of each of these switching elements, and a computer program for causing a computer to function to control a power supply device, A function of performing phase shift type PWM control for controlling the pulse width of the pulsed voltage output from the switching circuit by changing the phase of the ON / OFF cycle of the switching element; and the pulsed voltage output from the switching circuit When the duty ratio of the switching element is smaller than a predetermined value, the on / off cycle of each switching element is And a function of relatively reducing the frequency of the on / off cycle when the duty ratio is equal to or greater than the predetermined value. Computer program.

[0033] Further, the present invention includes an AC / DC converter that converts an AC voltage into a DC voltage, and a plurality of switching elements. When a DC voltage is input, each switching element is turned on and off. And a switching circuit that outputs a Norse voltage based on a combination of ON and OFF of each of these switching elements, and a computer program for causing a computer to function to control a power supply device, A function of performing phase shift type PWM control for controlling the pulse width of the pulsed voltage output from the switching circuit by changing the phase of the ON / OFF cycle of the switching element; and the pulsed voltage output from the switching circuit When the duty ratio of the switching element is smaller than the first value, In this case, the timing when all of the plurality of switching elements are turned off is inserted, and the duty ratio is less than a second value that is greater than or equal to the first value and greater than the first value. When the switching element is not turned off and the duty ratio is greater than or equal to the second value, the on / off cycle frequency is less than the second value. To make the computer realize the function of lowering the frequency of Is a computer program characterized by

Brief Description of Drawings

FIG. 1 is a block diagram showing a microwave plasma processing apparatus including a microwave generating apparatus equipped with a high voltage power supply according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining an internal configuration of the microwave plasma processing apparatus of FIG. 1.

FIG. 3A and FIG. 3B are circuit diagrams showing in detail a high-voltage power supply according to one embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a magnetron that is a main component of a microwave oscillating unit in the microwave plasma processing apparatus of FIG. 1.

FIG. 5 is a diagram showing an example of a relationship between a gate signal of each switching transistor and a transformer primary voltage waveform in normal phase shift PWM control.

FIG. 6 is a diagram schematically showing a one-cycle switching operation in the case of FIG. 5.

[Figure 7] Figure 7 shows the actual waveforms with duty ratios of 20%, 50%, and 90% when the duty ratio of the transformer primary voltage is changed in actual phase-shift PWM control. is there.

FIG. 8 is a diagram schematically showing a one-cycle switching operation in the switching circuit of the high-voltage power supply according to one embodiment of the present invention.

FIG. 9 is a schematic diagram showing an operating state of a switching circuit according to another embodiment of the present invention.

[Fig. 10] Fig. 10 shows the gate voltage, transformer primary-side current, when the duty ratio of the gate signal is small at the high frequency, and when multiple order (high order) resonance occurs when the transistor is OFF. It is a figure which shows the waveform of a transformer secondary side electric current.

FIG. 11 is a schematic diagram showing an example of an operating state of a switching circuit according to still another embodiment of the present invention.

FIG. 12 is a schematic diagram showing another example of the operation state of the switching circuit in still another embodiment of the present invention. FIG. 13 is a schematic diagram showing still another example of the operation state of the switching circuit according to still another embodiment of the present invention.

FIG. 14A and FIG. 14B are schematic diagrams showing an operating state of a switching circuit according to another embodiment of the present invention.

FIG. 15 is a schematic diagram showing an operation state of a switching circuit in still another embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a microwave plasma processing apparatus including a microwave generation apparatus equipped with a high voltage power supply (power supply apparatus) according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining the internal configuration.

As shown in FIG. 1, a microwave plasma processing apparatus 100 includes a microwave generator 1, a microphone mouth wave transmission unit 2, a plasma processing unit 3, and a higher-level control unit that controls these units. And an overall control unit 4.

The microwave generator 1 includes a high voltage power supply 11 and a microwave oscillating unit 12. As shown in Fig. 2, the high-voltage power supply 11 converts a three-phase 200V AC voltage into a DC voltage, boosts it, and supplies a predetermined DC voltage to the microwave oscillation unit 12. Circuit 13, AC / DC converter 14, switching circuit 15, high voltage step-up transformer 16, rectifier circuit 17, and high-voltage power supply controller 18 that mainly controls the switching circuit 15. Yes. The AC / DC converter 14 includes a rectifier circuit 21 and a smoothing circuit 22. Then, switching is performed (turned on and off) by the switching circuit 15 based on a command of 280 V DC voltage power and high voltage power supply controller 18 converted by the AC / DC converter 14. Then, the DC voltage is boosted to a desired voltage by the high voltage boosting transformer 16 and supplied to the microwave oscillating unit 12 via the rectifier circuit 17. The voltage / current of the high-voltage direct current supplied to the microwave oscillating unit 12 is monitored by the voltage / current monitor 20, and the information is sent to the high-voltage power supply controller 18.

As shown in FIG. 2, the microwave oscillating unit 12 includes a magnetron 23 that oscillates a microwave, a filament power supply 24 that supplies a voltage to the filament of the magnetron 23, and a microwave generator And a vibration unit controller 25.

[0039] Magnetron 23 is a filament as a cathode (force sword) in a container held in a vacuum.

26 and an anode 27. When a voltage is applied to the filament 26, thermionic electrons are emitted. By applying a predetermined voltage from the high-voltage power supply 11 between both electrodes, the flowing current is controlled. In addition, by rotating the magnetic field in a direction perpendicular to the electric field generated at this time, the thermoelectrons generate rotational motion and oscillate. As a result, the magnetron 23 generates microwaves of 2.45 GHz, for example.

[0040] The filament power supply 24 includes a high voltage step-down step-down transformer 28, an AC / DC conversion circuit 29, and a switching circuit 30 that step down a 200V alternating current extracted from a 200V three-phase alternating current. 7V DC voltage formed by high voltage step-down transformer 28 and AC / DC converter circuit 29 1S Controlled by switching circuit 30 based on command from microwave oscillator controller 25, predetermined range of 0-7V The voltage is applied to the filament 26 of the magnetron 23. The DC voltage / current supplied to the filament 26 is monitored by a voltage / current monitor 31, and the information is sent to the microwave oscillator controller 25.

[0041] The microwave transmission unit 2 is for guiding the microwave generated by the microwave generator 1 to the plasma processing unit 3, and guides the microwave generated by the microwave generator 1). Waveguide 32, isolator 33 for separating the reflected microwave, power sensor 34 for detecting the power of the microwave, tuner 35 for adjusting the impedance, and radiating the transmitted microwave to plasma processing unit 3 And a transmission unit controller 37 that controls each component of the microwave transmission unit 2. The antenna 36 has a slot for radiating microwaves. The power of the microwave detected by the power sensor 34 is monitored by the power monitor 38, and the signal is transmitted to the high voltage power controller 18.

[0042] The plasma processing unit 3 includes an airtightly configured chamber 39, a mounting table 40 on which a substrate S to be processed in the chamber 39 is mounted, and a microwave radiated from an antenna 36. A top plate 41 made of a dielectric material for transmitting waves into the chamber 39, a gas supply unit 42 for supplying a processing gas into the chamber 39, and a gas from the gas supply unit 42 is introduced into the chamber 39. A gas introduction member 43, an exhaust port 44 provided at the bottom of the chamber 39, An exhaust unit 45 that exhausts the inside of the chamber 39 through the air vent 44 and a processing unit controller 46 that controls each component of the plasma processing unit 3 are provided. When microwaves are radiated into the space above the substrate S to be processed in the chamber 39, plasma of the processing gas is formed in that space. A predetermined plasma process such as an oxidation process or etching is performed on the substrate S to be processed by the plasma.

[0043] The overall control unit 4 includes a high-level power supply controller 18, a microwave oscillation unit controller 25, a transmission unit controller 37, and a host controller 47 including a microprocessor (combiner) that controls the processing unit controller 46. An external interface 49 having a storage unit 48 storing various necessary programs and processing conditions so-called recipes, a setting unit for performing various settings such as the power of a high-voltage power supply, and a display unit for displaying status and alarms, etc. have. The recipe can be stored in a readable storage medium such as a CD-ROM, a hard disk, a flexible disk, and a nonvolatile memory. The overall control unit 4, the high voltage power supply controller 18, the microwave oscillation unit controller 25, the transmission unit controller 37, and the processing unit controller 46 constitute a control unit.

Next, the high voltage power supply 11 will be described in detail.

3A and 3B are circuit diagrams showing the high voltage power supply 11 in detail. As shown in Fig. 3A, the 200V three-phase AC power first passes through the safety circuit 13 to the AC / DC converter 14. The safety circuit 13 includes a breaker 50, a noise filter 51, and a magnetic contactor 52. The alternating current that has passed through this is converted to direct current by the rectifier circuit 21, and the direct current is smoothed by the smoothing circuit 22 having the capacitor 22a to obtain a direct current of 280V.

[0046] As shown in FIG. 3B, in the switching circuit 15, the four switching transistors Ql, Q2, Q3, and Q4 form a full-bridge circuit (also referred to as an H-bridge), and are phased by the high-voltage power controller 18. Shift-type PWM control is implemented. The switching transistors Ql, Q2, Q3, and Q4 receive the gate drive signals Vgl, Vg2, Vg3, and Vg4 from the high-voltage power supply controller 18 with a 50% duty ratio and controlled phase. It has become so. These are combined and a pulse voltage is output from the switching circuit 15. This Norse voltage force is taken as the transformer primary voltage. It is ejected.

[0047] Of the switching transistors Q1 and Q4, the transistor Ql Q4 has a positive output and the transistor Q2 Q3 has a negative output. As the switching transistor, a field effect transistor can be used from the viewpoint of efficiency, and a power MOS FET, which is preferably a MOS transistor, is preferable. In addition, an IGBT (insulated gate bipolar transistor), which has a higher breakdown voltage than a MOSFET and is suitable for high power, can be used.

[0048] The step-up transformer 16, which is the load of the switching circuit 15, is connected in series. In addition, a resonant capacitor Cr / 2 is inserted in parallel with each of the switching transistors Q1 and Q4, and a resonant inductor Lr is inserted in the wiring from the transistors Q1 and Q2 to the step-up transformer 16. Here, the resonant capacitor Cr / 2 is a combined capacitance of the parasitic capacitance of the transistor and an additional capacitor connected in parallel to the transistor, and the resonant inductor Lr is connected in series with the leakage inductance of the transformer 16 and the transformer. This is the combined inductance with the additional inductor. In the step-up transformer 16, the voltage is boosted to 280V power S-8000V. That is, a direct current having a voltage between 0 8000 V is rectified by the rectifier circuit 17 and supplied to the magnetron 23.

Next, the magnetron 23 that is the main component of the microwave oscillating unit 12 will be described with reference to FIG.

[0050] In the magnetron 23, a filament 26 as a cathode and an anode 27 disposed so as to face the cathode 26 are arranged in a case 61 made of metal, for example, kept in a vacuum. Actually, the filament 26 is formed into a cylindrical shape, and the anode 27 is formed into a coaxial cylindrical shape so as to surround the periphery thereof. In FIG. 4, the structure of the magnetron 23 is schematically shown. A plurality of cavity resonators 62 are provided on the surface of the anode 27 facing the filament 26.

[0051] A side surface 66 (upper and lower surfaces in the figure) 66 of the case 61 is formed of a non-magnetic material, and a permanent magnet 67 is disposed on the outside thereof. As a result, a strong magnetic field can be formed in the space between the filament 26 as the cathode and the anode 27 so as to be orthogonal to the opposing direction of these two electrodes. In addition, a voltage is applied to the filament 26 from the filament power supply 24, thereby releasing thermionic electrons. Is issued. A predetermined voltage is applied from the high-voltage power source 11 between the filament 26 functioning as a cathode and the anode 27, whereby the current is controlled. Since the magnetic field acts in a direction perpendicular to the electric field generated at this time, the orthogonal electromagnetic field causes rotational movement of the thermoelectrons emitted from the filament 26, and the thermoelectrons are hollow. Oscillation occurs when passing through the resonator 62. As a result, for example, 2.45 GHz microwaves are generated.

[0052] The anode 27 is connected to an antenna lead 64 that penetrates the case 61 via an insulating material 63. An antenna 65 is connected to the tip of the antenna lead 64, and the generated microphone mouth wave is propagated from the antenna 65 into the waveguide 32.

Next, a processing operation in the microwave plasma processing apparatus configured as described above will be described.

First, in the setting unit of the external interface 49, various settings such as the power of the high voltage power supply are performed. Then, the substrate to be processed S is loaded into the chamber 39 of the plasma processing unit 3 from a loading / unloading port (not shown). Then, a predetermined processing gas is introduced into the chamber 39 from the gas supply unit 42 via the gas introduction member 43, and a microphone mouth wave is generated by the microwave generator 1, and into the chamber 39 through the microwave transmission unit 2. Microwaves are emitted. As a result, the processing gas is turned into plasma in the chamber 39, and a predetermined plasma processing is executed by the microwave plasma.

At this time, control of the generated microwave is performed by the high voltage power supply controller 18 using the switching circuit 15 of the high voltage power supply 11 of the microwave generator 1. Specifically, the high voltage power supply controller 18 controls the switching frequency and phase (phase) of each switching transistor of the switching circuit 15 based on the setting signal from the external interface 49, and as described above, The switching operation is performed according to the shift type PWM control. At this time, the current and voltage signals from the current / voltage monitor 20 and the power signal detected by the power sensor 34 of the microwave transmission section 2 monitored by the power monitor 38 are fed back and set as set. Each switching transistor of the switching circuit 15 is controlled so that [0056] In a normal phase shift type PWM control switching operation, the gate signals of the switching transistors Ql, Q2, Q3, and Q4 are fixed to a duty ratio of 50%, for example, and their phases are shifted. The Then, by inserting an appropriate dead time, the voltage waveform of the step-up transformer 16—the secondary side is controlled as desired. That is, if the duty ratio in the voltage waveform applied to the primary side of the transformer 16 is small, the output is small, and if the duty ratio is large, the output is large. Figure 5 shows an example of the gate signal of each switching transistor and the transformer primary voltage waveform. In addition, Fig. 6 schematically shows the switching operation in one cycle in the case of Fig. 5. (In Fig. 6, for the sake of simplicity, the switching transistors Q1 to Q4 are depicted as simple open / close switches, and the transformer is shown as a box.) Partial force of (1) to (8) in Fig. 5 Correspond to the states (1) to (8). Here, the dead time is the state (2) (4) (6) (8) in Fig. 5. These can be omitted in the phase shift type PWM control. However, if these are omitted, for example, the transistors are switched from (1) to (3) in FIG. In this case, the transistor takes more time S when it is turned off than when it is turned on. For this reason, a short-circuit current may flow instantaneously through Q3 and Q4. Therefore, it is preferable to provide a dead time.

FIG. 7 shows actual waveforms when the switching transistors Q1 to Q4 are actually phase-shifted to change the duty ratio of the transformer primary voltage. Figure 7 shows real waveforms with duty ratios of 20%, 50%, and 90%. In FIG. 7, the time when Q1 and Q4 are both ON and the time force shaded area where both Q2 and Q3 are ON are shown.

In such a phase shift type PWM control, when a MOS type transistor is used as a switching transistor, when the off time is long, that is, the voltage output from this circuit and applied to the transformer 16 (output voltage) When the duty ratio is small, sufficient charge is not accumulated in the parasitic capacitance between the source and drain of the transistor that was turned on. For example, in the case of Fig. 6, when the duty ratio of the switching transistor Q2 in the states (1) to (3) is small, the charge is hardly accumulated in the parasitic capacitance part of Q2. After turning it off, it is connected in series to the switching transistor Q2. When the switching transistor Ql is turned on (state (5)), a large inrush current flows to the transistor Q1 through the capacitance part of the transistor Q2 that is turned off. This transistor generates heat and causes a large loss. End up. The same thing occurs in state (1). In this case, a large inrush current flows to the transistor Q2 through the capacitance portion of the transistor Q1 turned off, resulting in a large loss. That is, when the duty ratio of the output voltage from the switching circuit 15 is small, a large current flows through the switching transistors Q1 and Q2 to generate heat and generate a large loss.

Therefore, in the present embodiment, as shown in FIG. 8, the switching circuit is controlled by the high voltage power supply controller 18 so that all the switches are provided in the states (4) and (8). That is, in the state (4), the switching transistors Q2 and Q4 are temporarily turned off, and charges are accumulated in the parasitic capacitance. Therefore, no inrush current flows into transistor Q1 in state (5). In the state (8), the switching transistors Ql and Q3 are temporarily turned off, and charges are accumulated in the total capacity. Therefore, no inrush current flows into transistor Q2 in state (1). As described above, it is possible to eliminate the loss due to the inrush current in the switching transistors Ql and Q2. In FIG. 8, the period corresponding to (4) and (8) in FIG. 6 is omitted, and loss always occurs in the transistor and the switching circuit. Therefore, one cycle ((1) to (( Equivalent to 8)), it is desirable to reduce the number of switching times as much as possible. From this point of view, it is preferable that the period during which all the transistors are turned off is provided immediately before the period (1) and (5) in which the current flows to the load.

Here, in the case of FIG. 6 where there is no all-off time and the case of FIG. 8 where an all-off time is provided, a comparative experiment was performed by actually operating the transistors. In the experiment, the duty ratio of the output voltage from the switching circuit 15 was changed. Also, the temperature of the metal case of the transistor attached to the heat sink was measured, and when the temperature exceeded 100 ° C, the transistor failed, so the experiment was terminated near that temperature. The result It is shown in Table 1 below.

[table 1]

[0061] As shown in Table 1, it was confirmed that by providing an all-off time, heat generation of the transistor due to switching was suppressed.

Next, another embodiment will be described.

[0063] In the above embodiment, an all-off time for turning off all the switching transistors is provided. In this case, the switching operation per cycle increases twice. Therefore, when large power is supplied by increasing the duty ratio of the output voltage, the total loss may increase due to switching loss.

Yes

Therefore, in the present embodiment, the efficiency characteristics of the switching operation of the switching transistors Ql and Q2 are examined in advance. Then, as shown in FIG. 9, two patterns of phase shift type control are switched by the high voltage power supply controller 18 according to the load condition and the like. That is, in the region where the duty ratio of the output voltage is small, the phase shift type PWM control for forming the timing for turning off all the switching transistors is performed as described above. Phase-shift PWM control (Fig. 6) is performed. By such switching control, V and power supply control with less loss can be performed.

Next, still another embodiment will be described.

In the switching circuit 15, the resonance circuit is configured by inserting the resonance capacitor Cr / 2 and the resonance inductor Lr as described above so as to maintain as high efficiency as possible. The switching frequency (gate signal frequency) of each switching transistor is set to, for example, 10 to 500 kHz for the purpose of reducing the overall loss by reducing the copper loss of the transformer. However, at such a high frequency, when the duty ratio of the output voltage from the switching circuit 15 is small, a multiple order (high The following resonance may occur. Figure 10 shows the situation at that time. In the case shown in Fig. 10, even when the gate voltage is normal, the resonance current flows to the primary side of the transformer when the transistor is OFF. For this reason, voltage is also output on the secondary side of the transformer, and normal phase shift PWM control is not performed. In order to prevent such deterioration of power controllability, it is necessary to set the resonance frequency low. Since the resonance frequency fr is fr = l / (2π (LrCr) 1/2), it is necessary to set Lr and Cr large. Increasing the force and Cr is not preferable because, as described above, a large inrush current flows through the transistor connected in series when it is not charged and heat is generated. On the other hand, if Lr is increased, sufficient power cannot be obtained due to the influence of the resonant inductor connected in series with the transformer 16 in the high power mode (high power mode) in which the duty ratio of the output voltage from the switching circuit 15 is large. there is a possibility.

In such a high power mode, the power S can be increased by decreasing the switching frequency. In other words, since the impedance changes depending on the frequency, if the frequency is lowered, it becomes difficult to be affected by the resonant inductor, and a larger noise can be obtained.

[0068] Therefore, in the present embodiment, in the low power mode with a low duty ratio, for example, less than 50%, in which efficiency should be emphasized, the frequency is increased to, for example, about 50 to 100 kHz. In the case of a high power mode with a high duty ratio that requires emphasis on power, for example, 50% or more, control is performed so that the frequency is lowered to, for example, about 1 to 50 kHz. As a result, even in the low power mode where power controllability is a problem, it can operate without resonance, and in the high power mode where power is important, the inductance of the resonant inductor is reduced. High efficiency can be obtained. In this case, as shown in FIG. 11, the frequency is reduced to a constant value at a certain duty ratio or more, for example, 50% or more, or at a low duty ratio with low power, the frequency is fixed at a high frequency as shown in FIG. In a high power mode of a certain duty ratio or higher, for example, 50% or higher, the frequency decreases as the duty ratio increases, or even in a region where the duty ratio is smaller than the predetermined duty ratio as shown in FIG. As the value increases, the frequency can be lowered. By such a mode, as much as possible A large power can be obtained without reducing the efficiency.

[0069] Next, another embodiment will be described.

[0070] This embodiment is a combination of the above-described embodiments. For example, as shown in FIGS. 14A and 14B, in the low duty ratio in which the duty ratio is smaller than a predetermined value, the above-described embodiment is used. As described above, control is performed to set the timing for turning off all the switching transistors. When the duty ratio is equal to or higher than a predetermined duty ratio, the control is switched to the normal phase shift control and the frequency is lowered. Specifically, as shown in FIG. 14A, the frequency may be reduced to a constant value when the duty ratio is a predetermined value or more, or when the duty ratio is a predetermined value or more as shown in FIG. 14B. The frequency may be changed according to the duty ratio. Also, when the duty ratio is smaller than a predetermined value, the frequency may be changed according to the duty ratio.

Next, still another embodiment will be described.

In the present embodiment, as shown in FIG. 15, control is performed to provide timing for turning off the switching transistor at a low duty ratio smaller than the first duty ratio A, and the first duty ratio is set. Normal phase shift control is performed at a medium duty ratio that is greater than the ratio A and smaller than the second duty ratio B, and at a high duty ratio that is greater than the second duty ratio B than at the middle duty ratio. In addition, control to reduce the frequency is added. Thereby, finer control can be performed. In the present embodiment, the frequency change in the region of the second duty ratio or higher is the force S that changes the frequency according to the duty ratio in the case of FIG. 15, and the frequency is reduced to a constant value. Good. Also, control the frequency to a region that is greater than the first duty ratio and smaller than the second duty ratio! /, Smaller than the first duty ratio! /, Smaller than the frequency in the region! /, And the frequency. May be. Further, the frequency may be lowered as the duty ratio increases in a region that is greater than or equal to the first duty ratio and smaller than the second duty ratio. In this case, the frequency may be lowered as the duty ratio increases even in a region smaller than the first duty ratio.

It should be noted that the present invention can be variously modified without being limited to the above embodiments.

For example, in each of the above embodiments, the present invention is used in a microwave generator. However, the present invention is not limited to this, and the present invention can be applied to a power supply for other uses that require high voltage. Further, in each of the embodiments described above, the force using a full bridge circuit including four switching transistors as the switching circuit is not limited thereto, and, for example, a no-bridge bridge circuit may be used.

The present invention is suitable for a power source that requires a large amount of power, such as a microwave generator used in a microwave plasma processing apparatus.

Claims

The scope of the claims

[1] An AC / DC converter that converts AC voltage to DC voltage;

It has multiple switching elements, and when a DC voltage is input, an ON / OFF cycle occurs in each switching element, and a NOR voltage is output based on the ON / OFF combination of each switching element. A switching circuit to

A phase shift type that controls the pulse width of the Norse voltage output from the switching circuit by changing the phase of the ON / OFF cycle of each switching element.

A control unit that performs PWM control;

With

The control unit inserts a timing at which all of the plurality of switching elements are turned off in an on / off cycle of the switching elements.

A power supply device characterized by that.

[2] an AC / DC converter that converts AC voltage to DC voltage;

A control unit that performs phase shift type PWM control for controlling a pulse width of a Norse voltage output from the switching circuit by changing a phase of an ON / OFF cycle of each switching element;

With

When the duty ratio of the pulse voltage output from the switching circuit is smaller than a predetermined value, the control unit determines a timing at which all of the plurality of switching elements are turned off in the ON / OFF cycle of the switching elements. On the other hand, if the duty ratio is greater than or equal to the predetermined value, the timing when all of the plurality of switching elements are turned off is not inserted.

A power supply device characterized by that.

[3] an AC / DC converter that converts AC voltage to DC voltage;

Each of the switching elements when a DC voltage is input. A switching circuit that generates an on-off cycle based on a combination of on / off of each of these switching elements,

With

The control unit is configured to relatively increase the frequency of the on / off cycle of each switching element when the duty ratio of the pulse voltage output from the switching circuit is smaller than a predetermined value. On the other hand, when the duty ratio is greater than or equal to the predetermined value, the frequency of the on / off cycle is relatively lowered.

A power supply device characterized by that.

An AC / DC converter that converts AC voltage to DC voltage;

With

When the duty ratio of the pulse voltage output from the switching circuit is smaller than a predetermined value, the control unit determines a timing at which all of the plurality of switching elements are turned off in the ON / OFF cycle of the switching elements. On the other hand, when the duty ratio is greater than or equal to the predetermined value, the timing at which all the switching elements are turned off is not inserted, and the frequency of the on / off cycle is determined. Is made lower than the frequency when the duty ratio is smaller than the predetermined value.

A power supply device characterized by that. [5] When the duty ratio is greater than or equal to the predetermined value, the control unit performs control so that the frequency of the on / off cycle is lower if the duty ratio is larger.

The power supply device according to claim 3 or 4, wherein

[6] The control unit may determine that the duty cycle is smaller than a predetermined value! /, In some cases! /, But if the duty ratio is larger, the frequency of the on / off cycle is lower. To control

The power supply device according to claim 5, wherein:

[7] An AC / DC converter that converts AC voltage to DC voltage;

With

When the duty ratio of the pulse voltage output from the switching circuit is smaller than the first value, the control unit turns off the plurality of switching elements in the ON / OFF cycle of the switching elements. On the other hand, when the duty ratio is smaller than a second value that is greater than or equal to the first value and greater than the first value, the plurality of switching elements are all When the duty ratio is equal to or greater than the second value, the on / off cycle frequency is set to be less than the second value when the duty ratio is smaller than the second value. It is getting lower than the frequency

A power supply device characterized by that.

[8] When the duty ratio is equal to or greater than the second value, the control unit performs control so that the frequency of the on / off cycle is lower when the duty ratio is larger. Have The power supply device according to claim 7.

Even when the duty ratio is equal to or higher than the first value and smaller than the second value, the control unit has a lower frequency of the on / off cycle if the duty ratio is larger! I ’m going to control it.

The power supply device according to claim 8, wherein:

The control unit controls the frequency of the on / off cycle to be lower if the duty ratio is larger even when the duty ratio is smaller than the first value.

The power supply device according to claim 9, wherein:

The switching circuit has four switching elements, which constitute a full bridge circuit.

The power supply device according to claim 1, wherein the power supply device is a power supply device.

12. The power supply device according to claim 11, wherein the duty ratios of on / off cycles of the four switching elements are the same.

The switching element is a MOS FET or an IGBT.

Step-up transformer for stepping up a voltage output from the switching circuit

The power supply device according to claim 1, further comprising: A power supply device according to any one of claims 1 to 14,

A microwave generation unit comprising: a microwave oscillation unit that is supplied with power from the power supply unit and oscillates microwaves.

The microwave oscillation unit is

A chamber whose interior is maintained in a vacuum;

A filament disposed in the chamber that functions as a cathode for emitting thermal electrons;

An anode disposed opposite to the filament in the chamber and powered by the power supply to form an electric field with the filament;

Magnetic field generating means for forming a magnetic field orthogonal to the electric field outside the chamber; Equipped with a magnetron

16. The microwave generator according to claim 15, wherein

[17] An AC / DC converter that converts an AC voltage into a DC voltage and a plurality of switching elements. When a DC voltage is input, an ON / OFF cycle occurs in each of the switching elements. A computer program for causing a computer to function to control a power supply device comprising: a switching circuit that outputs a pulsed voltage based on a combination of ON and OFF of switching elements;

A function of performing phase shift type PWM control for controlling the pulse width of the Norse voltage output from the switching circuit by changing the phase of the ON / OFF cycle of each switching element;

A function of inserting a timing at which all of the plurality of switching elements are turned off in the ON / OFF cycle of the switching elements;

A computer program for causing a computer to realize the above.

[18] An AC / DC converter that converts an AC voltage into a DC voltage and a plurality of switching elements. When a DC voltage is input, an ON / OFF cycle occurs in each of the switching elements. A computer program for causing a computer to function to control a power supply device comprising: a switching circuit that outputs a pulsed voltage based on a combination of ON and OFF of switching elements;

When the duty ratio of the pulse voltage output from the switching circuit is smaller than a predetermined value, the timing at which all of the plurality of switching elements are turned off in the on / off cycle of the switching element is inserted, When the duty ratio is equal to or greater than the predetermined value, a function of not inserting a timing at which the plurality of switching elements are all turned off;

A computer program for causing a computer to realize the above.

[19] An AC / DC converter that converts AC voltage to DC voltage, and multiple switching elements Switching circuit that generates an on / off cycle when the DC voltage is input, and outputs a pulsed voltage based on the combination of ON / OFF of each switching element. And a computer program for causing a computer to function to control a power supply device comprising:

When the duty ratio of the pulsed voltage output from the switching circuit is smaller than a predetermined value, the frequency of the ON / OFF cycle of each switching element is relatively increased, and the duty ratio is equal to or higher than the predetermined value. And a function of relatively reducing the frequency of the on / off cycle,

A computer program for causing a computer to realize the above.

[20] An AC / DC converter that converts an AC voltage into a DC voltage and a plurality of switching elements. When a DC voltage is input, an ON / OFF cycle occurs in each of the switching elements. A computer program for causing a computer to function to control a power supply device comprising: a switching circuit that outputs a pulsed voltage based on a combination of ON and OFF of switching elements;

When the duty ratio of the pulse voltage output from the switching circuit is smaller than the first value, the timing at which all of the plurality of switching elements are turned off in the ON / OFF cycle of the switching element is inserted. When the duty ratio is greater than or equal to the first value and smaller than the second value that is greater than the first value, the timing at which all of the plurality of switching elements are turned off is not inserted, and the duty ratio is A function of making the frequency of the on / off cycle lower than the frequency when the duty ratio is smaller than the second value when the second value or more;

A computer program for causing a computer to realize the above.