KR20090055630A - Power supply and microwave generator using same - Google Patents

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

Power supply unit and microwave generating device using the same {POWER SUPPLY AND MICROWAVE GENERATOR USING SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply apparatus having a switching circuit for performing a switching operation by phase shift type PWM control, and a microwave generating apparatus using the power supply apparatus.

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

As a method of generating a plasma in a plasma processing apparatus, a method of generating a plasma by capacitive coupling between parallel plate electrodes by supplying a processing gas into a chamber in which the parallel plate electrodes are arranged, and supplying predetermined power to the parallel plate electrodes. This has been used a lot. However, in recent years, as a plasma capable of realizing high plasma density and low electron temperature, a method using microwaves has been attracting attention.

As a plasma source using microwaves, it is common to use a microwave generator provided with a magnetron. The magnetron is constructed by arranging a positive electrode (anode) having a cavity resonator in a coaxial shape around the filament as the negative electrode (cathode). In a state where a direct current electric field is applied to both of these electrodes, the cathode is heated to emit hot electrons. By adjusting the electric field (voltage) applied between both electrodes, the electric current which flows is controlled. At the same time, a rotary motion occurs and the oscillation occurs in the hot electrons by the magnetic field applied in the direction orthogonal to the electric field. As a result, microwaves are generated.

The use of magnetrons in microwave oscillators requires large, high-voltage power supplies. The switching circuit of 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 and current can be freely set by the number of turns of the transformer.

Power control of a power supply using such a switching circuit is generally performed by PWM (Pulse Width Modulation) control. This control is conventionally performed by adjusting the on / off time (duty cycle) of a transistor. However, when all the transistors are turned off for a long time, the potential of the line under load becomes unstable and the switching loss increases.

As a technique for avoiding such a bad situation, a phase shift type PWM control is known in which the ON time of each transistor is controlled by shifting the phase (phase) by making the duty ratio of the gate signal of each transistor constant. Technology June 2004, pages 228-235 (Non-Patent Document 1). By performing the phase shift type PWM control, the resonant circuit can be easily formed, so that an efficient switching operation can be performed.

In the case of performing phase shift PWM control using the full bridge circuit as described above, MOS transistors with high switching efficiency are frequently used. However, when the off time is long, i.e., when the duty ratio of the voltage signal output from the circuit and applied to the load is small, the charges are not sufficiently accumulated in the parasitic capacitance portion between the source and the drain of the transistor which is turned on. Therefore, when this is turned off, when another transistor connected in series with this transistor is turned on, a large inrush current flows to the transistor in the on state through the capacitor portion of the transistor turned off, and these transistors generate heat. As a result, a large loss occurs.

On the other hand, when the duty ratio of the voltage signal applied to the load is large, larger power is required. However, in the normal phase shift control, the efficiency is lowered, and power may not be sufficiently obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and provides a power supply device having a high efficiency and a high-efficiency power supply device having a small effect of losses such as heat generation while operating the switching circuit by phase shift type PWM control. For the purpose of

In addition, another object of the present invention is to provide a power supply unit having a high efficiency and high power while operating a switching circuit by phase shift type PWM control, and a microwave generator using the power supply unit.

It is also an object to provide a computer program for controlling the switching circuit of such a power supply.

The present invention has an AC / DC converter for converting an AC voltage into a DC voltage and a plurality of switching elements, and when the DC voltage is input, an ON / OFF cycle occurs in each of the switching elements. Phase shift type PWM control which controls the pulse width of the pulse shape voltage output from the said switching circuit by changing the phase of the switching circuit which outputs a pulse shape voltage based on a combination of OFF and said on-off cycle of each said switching element. And a control unit for performing the control, wherein 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 element.

According to the present invention, in the on / off cycle of the switching element, the timing at which all the switching elements are turned off is inserted, so that the parasitic capacitance of the switching transistor can be sufficiently charged during the operation. Thereby, for example, in the switching transistor, it is possible to prevent the generation of the inrush current due to the small charge charge. For this reason, the loss by the inrush current, the heat generation of the transistor, and the like can be suppressed.

In addition, the present invention has an AC / DC converter for converting an AC voltage into a DC voltage and a plurality of switching elements, and when the DC voltage is input, an on / off cycle occurs in each of the switching elements. A phase shift type for controlling a pulse width of a pulsed voltage output from the switching circuit by changing a phase of an on / off cycle of each switching element and a switching circuit for outputting a pulsed voltage based on a combination of on and off. And a control unit that performs PWM control, wherein the control unit is configured to turn off all of the plurality of switching elements in an on / off cycle of the switching element when the duty ratio of the pulse shape voltage output from the switching circuit is smaller than a predetermined value. When the timing is set to be inserted, and the duty ratio is equal to or larger than the predetermined value, A power supply unit, characterized in that a plurality of switching elements are both not insert timing is turned off.

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

In addition, the present invention has an AC / DC converter for converting an AC voltage into a DC voltage and a plurality of switching elements, and when the DC voltage is input, an on / off cycle occurs in each of the switching elements. A phase shift type for controlling a pulse width of a pulsed voltage output from the switching circuit by changing a phase of an on / off cycle of each switching element and a switching circuit for outputting a pulsed voltage based on a combination of on and off. And a control unit for performing PWM control, wherein the control unit relatively increases the frequency of the on / off cycles of the respective switching elements when the duty ratio of the pulse shape voltage output from the switching circuit is smaller than a predetermined value. When the duty ratio is equal to or greater than the predetermined value, the frequency of the on / off cycle is compared. That is to low to a power supply device according to claim.

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 high, and when the duty ratio is equal to or greater than the predetermined value, the on The frequency of the off cycle becomes relatively low. As a result, good power control performance is achieved in the low power mode, and high efficiency can be obtained in the high power mode.

In this case, when the duty ratio is greater than or equal to the predetermined value, the controller may control the frequency of the on / off cycle to be lower if the duty ratio is larger. Furthermore, even if the duty ratio is smaller than the predetermined value, the control unit may control the frequency of the on / off cycle to be lower if the duty ratio is larger.

In addition, the present invention has an AC / DC converter for converting an AC voltage into a DC voltage and a plurality of switching elements, and when the DC voltage is input, an on / off cycle occurs in each of the switching elements. A phase shift type for controlling a pulse width of a pulsed voltage output from the switching circuit by changing a phase of an on / off cycle of each switching element and a switching circuit for outputting a pulsed voltage based on a combination of on and off. And a control unit for performing PWM control, wherein the control unit is configured to turn off all of the plurality of switching elements in an on / off cycle of the switching element when the duty ratio of the pulse shape voltage output from the switching circuit is smaller than a predetermined value. In the case where the duty ratio is equal to or greater than the predetermined value, A plurality of switching elements do not all inserts the timing is turned off, is also a power supply unit, it characterized in that it is lower than the frequency of the turning on and small when the frequency of the off-cycle than the duty ratio of the predetermined value.

According to the present invention, more precise control can be performed, and both efficiency and power controllability can be achieved at a high level.

In this case, when the duty ratio is greater than or equal to the predetermined value, the control unit may control the frequency of the on / off cycle to be lower if the duty ratio is larger. Furthermore, even when the duty ratio is smaller than a predetermined value, the control unit may control the frequency of the on / off cycle to be lower if the duty ratio is larger.

In addition, the present invention has an AC / DC converter for converting an AC voltage into a DC voltage and a plurality of switching elements, and when the DC voltage is input, an on / off cycle occurs in each of the switching elements. A phase shift type for controlling a pulse width of a pulsed voltage output from the switching circuit by changing a phase of an on / off cycle of each switching element and a switching circuit for outputting a pulsed voltage based on a combination of on and off. And a control unit that performs PWM control, and wherein the control unit has a plurality of switching elements in an on / off cycle of the switching element when the duty ratio of the pulse shape voltage output from the switching circuit is smaller than a first value. Insert a timing of turning off, while the duty ratio is equal to or greater than the first value and the first When the second value is smaller than the second value, the timing at which the plurality of switching elements are all turned off is not inserted. When the duty ratio is equal to or greater than the second value, the frequency of the on / off cycle is set to the duty ratio. The power supply device is characterized by being lower than the frequency in the case of smaller than the second value.

According to the present invention, more precise control can be performed, and both efficiency and power controllability can be achieved at a high level.

In this case, when the duty ratio is greater than or equal to the second value, the controller may be configured to control the frequency of the on / off cycle to be lower if the duty ratio is larger. Furthermore, even if the duty ratio is greater than or equal to the first value and smaller than the second value, the control unit may control the frequency of the on / off cycle to be lower if the duty ratio is larger. Furthermore, even if the duty ratio is smaller than the first value, the control unit may control the frequency of the on / off cycle to be lower if the duty ratio is larger.

In each of the above inventions, suitably, the switching circuit has four switching elements, and these constitute a full bridge circuit. Preferably, the duty ratios of the on / off cycles of the four switching elements are the same.

Also, for example, the switching element is a MOS FET or IGBT. In addition, a boost transformer for boosting the voltage output from the switching circuit may be further provided.

In addition, the present invention is a microwave generating device comprising a power supply device having any one of the above-mentioned characteristics and a microwave oscillation unit which is fed from the power supply device and oscillates microwaves.

Preferably, the microwave oscillation portion is disposed opposite to the filament in the chamber, the filament being disposed in the chamber, the filament serving as a cathode for dissipating hot electrons, and being fed from the power supply device. And a magnetron having an anode for forming an electric field between the filaments and a magnetic field generating means for forming a magnetic field orthogonal to the electric field outside the chamber.

In addition, the present invention has an AC / DC converter for converting an AC voltage into a DC voltage and a plurality of switching elements, and when the DC voltage is input, an on / off cycle occurs in each of the switching elements. A computer program for causing a computer to control a power supply having a switching circuit that outputs a pulsed voltage based on a combination of on and off, the computer program being configured to change the phase of the on / off cycle of each switching element from the switching circuit. A phase shift type PWM control for controlling the pulse width of an output pulse shape voltage and a function of inserting a timing at which all of the plurality of switching elements are turned off in an on / off cycle of the switching elements are provided to the computer. It is a computer program characterized by realization.

In addition, the present invention has an AC / DC converter for converting an AC voltage into a DC voltage and a plurality of switching elements, and when the DC voltage is input, an on / off cycle occurs in each of the switching elements. A computer program for causing a computer to control a power supply having a switching circuit that outputs a pulsed voltage based on a combination of on and off, the computer program being configured to change the phase of the on / off cycle of each switching element from the switching circuit. In the on / off cycle of the switching element, the function of performing phase shift PWM control for controlling the pulse width of the output pulse shape voltage and the duty ratio of the pulse shape voltage output from the switching circuit are smaller than a predetermined value. Inserting a timing at which all of the plurality of switching elements are turned off; The computer program is characterized in that the computer realizes a function of not inserting a timing at which all of the plurality of switching elements are turned off when the TV is equal to or larger than the predetermined value.

In addition, the present invention has an AC / DC converter for converting an AC voltage into a DC voltage and a plurality of switching elements, and when the DC voltage is input, an on / off cycle occurs in each of the switching elements. A computer program for causing a computer to control a power supply having a switching circuit that outputs a pulsed voltage based on a combination of on and off, the computer program being configured to change the phase of the on / off cycle of each switching element from the switching circuit. A function for performing phase shift PWM control for controlling the pulse width of the output pulse shape voltage, and the frequency of the on / off cycles of the respective switching elements when the duty ratio of the pulse shape voltage output from the switching circuit is smaller than a predetermined value. Is relatively high, and when the duty ratio is equal to or greater than the predetermined value, , A computer program that functions to relatively low frequency of the off-cycle characterized by realizing in the computer.

In addition, the present invention has an AC / DC converter for converting an AC voltage into a DC voltage and a plurality of switching elements, and when the DC voltage is input, an on / off cycle occurs in each of the switching elements. A computer program for causing a computer to control a power supply having a switching circuit that outputs a pulsed voltage based on a combination of on and off, the computer program being configured to change the phase of the on / off cycle of each switching element from the switching circuit. The phase shift type PWM control for controlling the pulse width of the output pulse shape voltage, and the duty cycle of the pulse shape voltage outputted from the switching circuit is smaller than the first value, the on / off cycle of the switching element. And inserting a timing at which the plurality of switching elements are all turned off, and the duty ratio When the value is greater than the first value and smaller than the second value larger than the first value, the timing for turning off the plurality of switching elements is not inserted. When the duty ratio is equal to or greater than the second value, the on / off cycle A computer program for causing a computer to realize a function of making a frequency lower than a frequency when the duty ratio is smaller than the second value.

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

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

3 (a) and 3 (b) is a circuit diagram specifically showing a high voltage power supply according to an embodiment of the present invention;

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

5 is a view showing an example of the relationship between the gate signal of each switching transistor and the transformer primary voltage waveform in normal phase shift type PWM control;

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

Fig. 7 is a diagram showing actual waveforms of 20%, 50%, and 90% duty ratio when the duty ratio of the transformer primary side voltage is changed in the actual phase shift type PWM control.

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

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

FIG. 10 shows the gate voltage, the transformer primary side current, and the transformer secondary side current when the duty ratio of the gate signal is small at a high frequency and when the transistor is OFF and a resonance of a plurality of orders (higher order) occurs. Drawing representing waveform,

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;

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

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

14 (a) and 14 (b) are schematic diagrams showing an operating state of a switching circuit in another embodiment of the present invention;

Fig. 15 is a schematic diagram showing an operating state of a switching circuit according to still another embodiment of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, one Example of this invention is described in detail, referring an accompanying drawing. 1 is a block diagram showing a microwave plasma processing apparatus including a microwave generating device equipped with a high voltage power supply (power supply device) according to an embodiment of the present invention. 2 is a schematic view for explaining the internal configuration thereof.

As shown in FIG. 1, the microwave plasma processing apparatus 100 includes a microwave control apparatus 1, a microwave transmission unit 2, a plasma processing unit 3, and an overall control unit that is an upper control unit that controls these units. (4) is provided.

The microwave generator 1 includes a high voltage power supply 11 and a microwave oscillation unit 12. As shown in FIG. 2, the high voltage power supply 11 converts an AC voltage of three-phase 200V into a DC voltage, boosts the voltage, and supplies a predetermined DC voltage to the microwave oscillator 12. A high-voltage power supply for controlling the 13, the AC / DC converter 14, the switching circuit 15, the high breakdown voltage transformer 16, the rectifier circuit 17, and the switching circuit 15 mainly. It has a controller 18. The AC / DC converter 14 has a rectifier circuit 21 and a smoothing circuit 22. Then, the 280V DC voltage converted by the AC / DC converter 14 is switched (turned on and off) by the switching circuit 15 based on the command from the high voltage power supply controller 18. The DC voltage is boosted to the desired voltage by the high breakdown voltage transformer 16 and supplied to the microwave oscillator 12 through the rectifier circuit 17. The voltage and current of the high voltage direct current supplied to the microwave oscillation unit 12 are monitored by the voltage and current monitor 20, and the information is sent to the high voltage power supply controller 18.

As shown in FIG. 2, the microwave oscillator 12 includes a magnetron 23 for oscillating microwaves, a filament power supply 24 for supplying voltage to the filament of the magnetron 23, and a microwave oscillator controller 25. have.

The magnetron 23 has a filament 26 as a cathode (cathode) and an anode (anode) 27 in a container held in a vacuum. When a voltage is applied to the filament 26, hot 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 applying a magnetic field in a direction orthogonal to the electric field generated at this time, rotational movement occurs in the hot electrons and oscillates. As a result, the magnetron 23 generates microwaves of 2.45 GHz, for example.

The filament power supply 24 has a high breakdown voltage transformer 28 for lowering the 200V AC taken out from a 200V three-phase alternating current, an AC / DC converter circuit 29, and a switching circuit 30. have. The 7V DC voltage formed by the high breakdown voltage transformer 28 and the AC / DC conversion circuit 29 is controlled by the switching circuit 30 based on the instruction from the microwave oscillator controller 25, and the range of 0-7V. It becomes a predetermined voltage of and is applied to the filament 26 of the magnetron 23. On the other hand, the voltage and current of the DC supplied to the filament 26 are monitored by the voltage and current monitor 31, and the information is sent to the microwave oscillation unit controller 25.

The microwave transmission unit 2 is for guiding the microwaves generated by the microwave generator 1 to the plasma processor 3, and the waveguide 32 for guiding the microwaves (μ) generated by the microwave generator 1. And an isolator 33 for separating the reflected microwave, a power sensor 34 for detecting the power of the microwave, a tuner 35 for adjusting the impedance, and for transmitting the transmitted microwaves to the plasma processing unit 3. An antenna 36 and a transmitter controller 37 for controlling each component of the microwave transmitter 2 are provided. The antenna 36 is formed with a slot for emitting microwaves. The power of the microwaves detected by the power sensor 34 is monitored by the power monitor 38, and the signal is transmitted to the high voltage power supply controller 18.

The plasma processing unit 3 includes a chamber 39 that is hermetically sealed, a mounting table 40 on which a substrate S to be subjected to plasma processing is performed in the chamber 39, and microwaves radiated from the antenna 36. The ceiling plate 41 made of a dielectric material for permeating the gas into the chamber 39, the gas supply part 42 for supplying the processing gas into the chamber 39, and the gas from the gas supply part 42. A gas introduction member 43 introduced into the inside, an exhaust port 44 provided at the bottom of the chamber 39, an exhaust part 45 for exhausting the inside of the chamber 39 through the exhaust port 44, and a plasma processing unit ( It has the processing part controller 46 which controls each component of 3). Microwaves are emitted to the upper space of the substrate S in the chamber 39, whereby plasma of the processing gas is formed in the space. By this plasma, predetermined plasma processing, such as an oxidation process and an etching, is performed to the to-be-processed substrate S. FIG.

The overall controller 4 includes an upper controller 47 comprising a high voltage power supply controller 18, a microwave oscillator controller 25, a transmitter controller 37, and a microprocessor (computer) for controlling the processor controller 46; An external interface 49 having a storage unit 48 for storing various programs and processing conditions, so-called recipes required for control, a setting unit for setting various kinds of power such as high voltage power, a display unit for displaying statuses and alarms, and the like. Have The recipe may be stored in a readable storage medium such as a CD-ROM, a hard disk, a flexible disk, a nonvolatile memory, or the like. The control part is comprised from the whole control part 4, the high voltage power supply controller 18, the microwave oscillation part controller 25, the transmission part controller 37, and the processing part controller 46.

Next, the high voltage power supply 11 is demonstrated in detail.

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

As shown in Fig. 3B, in the switching circuit 15, four switching transistors Q1, Q2, Q3, and Q4 constitute a full bridge circuit (also referred to as an H bridge), and a high voltage power supply controller ( 18), phase shift type PWM control is performed. Gate drive signals Vg1, Vg2, Vg3, and Vg4 having a 50% duty ratio whose phase (phase) is controlled are input to the switching transistors Q1, Q2, Q3, and Q4 from the high voltage power supply controller 18, respectively. have. These are synthesized and the pulse shape voltage is output from the switching circuit 15. This pulse shape voltage is taken out as a transformer primary side voltage.

Of the switching transistors Q1 to Q4, the transistors Q1 and Q4 are positive outputs, and the transistors Q2 and Q3 are negative outputs. As a switching transistor, a field effect transistor can be used from a viewpoint of efficiency, It is preferable that it is a MOS type, and a power MOSFET is suitable. In addition, an IGBT (insulated gate type bipolar transistor) suitable for high power withstand voltage compared to the MOS FET can also be used.

The boost transformer 16 serving as the load of the switching circuit 15 is connected to wirings extending from between the transistors Q1 and Q2 connected in series and between the transistors Q3 and Q4, respectively. In addition, the resonant capacitor Cr / 2 is inserted in parallel with each of the switching transistors Q1 to Q4, and the resonant inductor Lr is inserted into the wiring leading to the boost transformer 16 between the transistors Q1 and Q2. have. Here, the resonant capacitor Cr / 2 is the combined capacitance of the parasitic capacitance of the transistor and the additional capacitor connected in parallel to the transistor, and the resonant inductor Lr is an additional in series connected to the leakage inductance of the transformer 16 and the transformer. The composite inductance of the inductor. In the boost transformer 16, 280V is boosted to -8000V. That is, direct current | voltage of the voltage between 0-8000V is rectified by the rectifier circuit 17, and is supplied to the magnetron 23. As shown in FIG.

Next, the magnetron 23 which is a main component of the microwave oscillation part 12 is demonstrated with reference to FIG.

In this magnetron 23, a filament 26 as a cathode and an anode 27 disposed to face each other are disposed in a metal casing 61 held in a vacuum. In reality, 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, but the structure of the magnetron 23 is schematically described in FIG. 4. A plurality of cavity resonators 62 are provided on the surface of the anode 27 facing the filament 26.

The side surface (upper and lower surface in the figure) 66 of the case 61 is made of a nonmagnetic material, and a permanent magnet 67 is disposed outside thereof. Thereby, a strong magnetic field can be formed in the space between the filament 26 and the anode 27 as a cathode so as to be orthogonal to the opposing directions of these electrodes. In addition, a voltage is applied to the filament 26 from the filament power source 24, whereby hot electrons are emitted. In addition, a predetermined voltage is applied from the high voltage power supply 11 between the filament 26 and the anode 27 serving as the cathode, thereby controlling the current. Since the magnetic field acts in a direction orthogonal to the electric field generated at this time, a rotational motion occurs in the hot electrons emitted from the filament 26 by the orthogonal electromagnetic field, and the hot electrons pass through the cavity resonator 62. An oscillation occurs at the time, and as a result, microwaves of, for example, 2.45 GHz are generated.

The antenna lead 64 penetrating the case 61 through the insulating material 63 is connected to the anode 27. An antenna 65 is connected to the distal end of the antenna lead 64 so that the generated microwaves propagate from the antenna 65 into the waveguide 32.

Next, the 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 power of a high voltage power supply are made. Then, the substrate S to be processed is loaded into the chamber 39 of the plasma processing unit 3 from a carry-out port not shown. Then, a predetermined processing gas is introduced into the chamber 39 from the gas supply part 42 through the gas introducing member 43, microwaves are generated by the microwave generating device 1, and then through the microwave transmitting part 2. Microwaves are emitted in the chamber 39. As a result, the processing gas is converted into plasma in the chamber 39, and predetermined plasma processing is performed by the microwave plasma.

At this time, the control of the generated microwaves 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, phase (phase), etc. of each switching transistor of the switching circuit 15 based on the setting signal from the external interface 49, as described above. The switching operation is performed according to the phase shift type PWM control. At this time, the signal of the current and voltage from the current / voltage monitor 20 and the signal of the power detected by the power sensor 34 of the microwave transmission part 2 monitored by the power monitor 38 are fed back, Each switching transistor of the switching circuit 15 is controlled so that power as it is set is supplied.

In the switching operation by normal phase shift type PWM control, the gate signals of the switching transistors Q1, Q2, Q3 and Q4 are fixed at 50% duty ratio, for example, and these phases (phases) are shifted. By inserting the appropriate dead time, the voltage waveform on the primary side of the boost transformer 16 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. An example of the gate signal and the transformer primary voltage waveform of each switching transistor is schematically shown in FIG. 5. In addition, the switching operation of 1 cycle in the case of FIG. 5 is typically shown in FIG. (In Fig. 6, for the sake of simplicity, the switching transistors Q1 to Q4 are shown as simple open / close switches, and the transformer is shown as a rectangle.) Parts (1) to (8) of Fig. 5 are shown as (1) in Fig. 6. It corresponds to the state of (8), respectively. Here, dead time is a state of (2), (4), (6), and (8) in FIG. These may be omitted in the phase shift type PWM control. However, in the case where these are omitted, for example, transistors are different from (1) to (3) in FIG. In this case, the transistor takes longer to turn off than to turn on. For this reason, there exists a possibility that a short circuit current may flow through Q3 and Q4 instantaneously. Therefore, it is desirable to provide a dead time.

7 shows an actual waveform in the case where the duty ratio of the transformer primary side voltage is changed by actually phase shifting each of the switching transistors Q1 to Q4. 7 shows actual waveforms with duty ratios of 20%, 50% and 90%. In FIG. 7, the time when Q1 and Q4 are ON together and the time when both Q2 and Q3 are ON are shown by the oblique part.

In such phase shift type PWM control, when the MOS transistor is used as the switching transistor, when the off time is long, that is, when the duty ratio of the voltage (output voltage) output from this circuit and applied to the transformer 16 is small, Electric charges are not accumulated sufficiently in the parasitic capacitance portion between the source and the drain of the transistor which is turned on. For example, in the case of Fig. 6, the switching transistor Q2 is on in the states (1) to (3), but when the duty ratio is small, almost no charge is accumulated in the parasitic capacitance portion of Q2. When this is turned off, when the switching transistor Q1 connected in series with the switching transistor Q2 is turned on (state (5)), the transistor Q1 is turned through the capacitor portion of the transistor Q2 turned off. ), A large inrush current flows, and this transistor generates heat, resulting in a large loss. The same thing occurs even in the state (1). In this case, a large inrush current flows through the transistor Q2 through the capacitor portion of the transistor Q1 turned off, resulting in a large loss. In other words, 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, which causes a large loss.

Therefore, in this embodiment, as shown in Fig. 8, in the states (4) and (8), an all-off time is provided in which all the switching transistors are turned off. In order to provide such a state, the switching circuit is controlled by the high voltage power supply controller 18. That is, in the state (4), the switching transistors Q2 and Q4 are temporarily turned off and all the switching transistors are turned off, so that electric charges are collected in the parasitic capacitance of the switching transistor Q2. Therefore, in state (5), no inrush current flows into the transistor Q1. Further, in the state (8), by temporarily turning off the switching transistors Q1 and Q3 and turning off all the switching transistors, charges are collected in the parasitic capacitance of the switching transistor Q1. Therefore, in state (1), no inrush current flows into the transistor Q2. As described above, the loss due to the inrush current in the switching transistors Q1 and Q2 can be eliminated. On the other hand, in FIG. 8, the period corresponding to FIG. 6 (4) and (8) is abbreviate | omitted and the frequency | count of switching of a transistor is reduced. When the transistor switches, a loss always occurs in the transistor and the switching circuit. Therefore, it is preferable that the number of times of switching in one cycle (corresponding to (1) to (8) in FIG. 8) be minimized. From this point of view, it is preferable that the period in which all the transistors are turned off is provided immediately before the periods (1) and (5) in which current flows to the load.

Here, in the case of FIG. 6 without the all-off time and the case of FIG. 8 with the all-off time, a comparison experiment was conducted by actually operating the transistor. As an experiment, the duty ratio of the output voltage from the switching circuit 15 was changed. In addition, since the temperature of the metal case of the transistor attached to the heat sink was measured, and the temperature exceeded 100 ° C., the transistor failed, so the experiment was terminated in the vicinity of the temperature. The results are shown in Table 1 below.

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

Next, another Example is described.

In this embodiment, an all-off time is provided in which all switching transistors are all turned off. In this case, the switching operation is increased twice per cycle. Therefore, when the duty ratio of the output voltage is increased and a large amount of power is supplied, there is a possibility that the total loss is rather large due to the switching loss.

Therefore, in this embodiment, the efficiency characteristic of the switching operation of the switching transistors Q1 and Q2 is examined in advance. Then, as shown in Fig. 9, the phase shift type control of the two patterns is switched by the high voltage power supply controller 18 according to the load situation or the like. That is, in the region where the duty ratio of the output voltage is small, as described above, phase shift type PWM control in a mode for forming a timing for turning off all switching transistors is performed. When a predetermined duty ratio is reached, normal phase shift type PWM control is reached. Fig. 6 is performed. By such switching control, power loss control with less loss can be performed.

Next, another Example is described.

In the switching circuit 15, the resonant circuit is formed by inserting the resonant capacitor Cr / 2 and the resonant inductor Lr as described above so as to maintain the extremely high efficiency. The switching frequency (frequency of the gate signal) of each switching transistor is set to 10 to 500 kHz, for example, in order to reduce the copper loss of the transformer and reduce the total loss. However, at such a high frequency, when the duty ratio of the output voltage from the switching circuit 15 is small, resonance of a plurality of orders (higher orders) may occur when the transistor is turned off. 10 shows the shape at that time. In FIG. 10, even when the gate voltage is normal, a resonance current flows to the transformer primary side when the transistor is turned off. For this reason, a voltage is output also in the transformer secondary side, and normal phase shift type PWM control is not performed. In order to prevent such deterioration of power controllability, the resonance frequency should be set low. Since the resonance frequency fr is fr = 1 / (2π (LrCr) 1/2), it is necessary to set Lr and Cr large. However, it is not preferable to increase Cr because a large inrush current flows to the transistor connected in series when it is not charged, as described above, and generates heat. On the other hand, when Lr is increased, sufficient power can be obtained under the influence of the resonance inductor connected in series with the transformer 16 in a power mode (high power mode) in which the duty ratio of the output voltage from the switching circuit 15 is large. There is no possibility.

In such a large power mode, the power obtained by lowering the switching frequency can be increased. That is, since the impedance changes with frequency, the lowering of the frequency makes it less likely to be affected by the resonant inductor, thereby obtaining a larger power.

Therefore, in this embodiment, in the case of a low duty ratio that needs to focus on efficiency, for example, a low power mode of less than 50%, the frequency is set to high, for example, about 50 to 100 kHz, while the high duty needs to focus on power. In the case of a high power mode of, for example, 50% or more, the control is performed so that the frequency is low, for example, about 1 to 50 kHz. As a result, even in the low power mode where the power controllability is a problem, the resonance can be operated without occurrence. In the high power mode where power is important, high efficiency can be obtained by reducing the inductance of the resonant inductor. In this case, as shown in Fig. 11, at a certain duty ratio or higher, for example, 50% or more, the frequency is decreased to a constant value, or as shown in Fig. 12, at a low duty ratio of low power, at a high frequency. In the high-power mode above a certain duty ratio, for example, 50% or more, the frequency decreases as the duty ratio increases, or as the duty ratio increases, even in a region smaller than the predetermined duty ratio, as shown in FIG. You can lower or lower the frequency. In such a state, a large power can be obtained without lowering the pole force efficiency.

Next, another Example is described.

This embodiment is a combination of the previous embodiments. For example, as shown in Figs. 14A and 14B, at a low duty ratio whose duty ratio is smaller than a predetermined value, all the switching as described above. The control for providing a timing for turning off the transistor is performed, and above the predetermined duty ratio, the control is switched to the normal phase shift type control, and the frequency is lowered. Specifically, as shown in Fig. 14A, when the duty ratio is equal to or greater than the predetermined value, the frequency may be lowered to a constant value. As shown in Fig. 14B, when the duty ratio is equal to or greater than the predetermined value, The frequency may be changed depending on the duty ratio. In addition, even when the duty ratio is smaller than a predetermined value, the frequency may be changed in accordance with the duty ratio.

Next, another Example is described.

In this embodiment, as shown in Fig. 15, at a low duty ratio smaller than the first duty ratio A, control is provided to establish a timing for turning off the switching transistor, and is equal to or greater than the first duty ratio A and the second duty ratio B. At smaller intermediate duty ratios, normal phase shift control is performed, and at higher duty ratios of greater than or equal to the second duty ratio B, control is made to make the frequency smaller than when it is an intermediate duty ratio. Thereby, finer control can be performed. In the present embodiment, the frequency is changed in the region of the second duty ratio or more in accordance with the duty ratio in the case of Fig. 15, but the frequency may be lowered to a constant value. In addition, in an area greater than or equal to the first duty ratio and smaller than the second duty ratio, control may be performed at a frequency smaller than the frequency in an area smaller than the first duty ratio. In addition, in an area larger than or equal to the first duty ratio and smaller than the second duty ratio, the frequency may be lowered as the duty ratio becomes larger. In this case, even in a region smaller than the first duty ratio, the frequency may be lowered as the duty ratio becomes larger.

In addition, this invention is not limited to each said embodiment, A various deformation | transformation is possible. For example, in each of the above embodiments, the present invention was used for a microwave generator, but the present invention is not limited to this, but can be applied to power supplies for other uses that require high voltage. In each of the above embodiments, a full bridge circuit equipped with four switching transistors is used as the switching circuit. However, the present invention is not limited thereto, and a half bridge circuit may be used, for example.

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

Claims (20)

An AC / DC converter for converting an AC voltage into a DC voltage, A switching circuit having a plurality of switching elements and generating an on / off cycle in each of the switching elements when a DC voltage is input, and outputting a pulsed voltage based on a combination of on and off of these switching elements; A control unit which performs a phase shift type PWM control that controls the pulse width of the pulse shape voltage output from the switching circuit by changing the phase of the on / off cycle of each switching element. Provided with The control unit is configured to insert a timing at which all of the plurality of switching elements are turned off in an on / off cycle of the switching element. Power supply characterized in that. An AC / DC converter for converting an AC voltage into a DC voltage, A switching circuit having a plurality of switching elements and generating an on / off cycle in each of the switching elements when a DC voltage is input, and outputting a pulsed voltage based on a combination of on and off of these switching elements; A control unit which performs phase shift type PWM control that controls the pulse width of the pulse shape voltage output from the switching circuit by changing the phase of the on / off cycle of each switching element. Provided with When the duty ratio of the pulse shape voltage output from the switching circuit is smaller than a predetermined value, the controller inserts a timing at which all of the plurality of switching elements are turned off in an on / off cycle of the switching element. 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. Power supply characterized in that. An AC / DC converter for converting an AC voltage into a DC voltage, A switching circuit having a plurality of switching elements and generating an on / off cycle in each of the switching elements when a DC voltage is input, and outputting a pulsed voltage based on a combination of on and off of these switching elements; A control unit which performs a phase shift type PWM control that controls the pulse width of the pulse shape voltage output from the switching circuit by changing the phase of the on / off cycle of each switching element. Provided with When the duty ratio of the pulse shape voltage output from the switching circuit is smaller than a predetermined value, the controller is configured to relatively increase the frequency of the on / off cycles of the respective switching elements, and the duty ratio is the predetermined value. In this case, the frequency of the on / off cycle is relatively low. Power supply characterized in that. An AC / DC converter for converting an AC voltage into a DC voltage, A switching circuit having a plurality of switching elements and generating an on / off cycle in each of the switching elements when a DC voltage is input, and outputting a pulsed voltage based on a combination of on and off of these switching elements; A control unit which performs a phase shift type PWM control that controls the pulse width of the pulse shape voltage output from the switching circuit by changing the phase of the on / off cycle of each switching element. Provided with When the duty ratio of the pulse shape voltage output from the switching circuit is smaller than a predetermined value, the controller inserts a timing at which all of the plurality of switching elements are turned off in an on / off cycle of the switching element. On the other hand, when the duty ratio is equal to or greater than the predetermined value, the timing at which the plurality of switching elements are all turned off is not inserted, and the frequency of the on / off cycle is lower than the frequency when the duty ratio is smaller than the predetermined value. To be Power supply characterized in that. The method according to claim 3 or 4, And the control unit is configured to control the frequency of the on / off cycle to be lower if the duty ratio is larger than the predetermined value. The method of claim 5, wherein The control unit is configured to control the frequency of the on / off cycle to be lower when the duty ratio is larger even when the duty ratio is smaller than a predetermined value. An AC / DC converter for converting an AC voltage into a DC voltage, A switching circuit having a plurality of switching elements and generating an on / off cycle in each of the switching elements when a DC voltage is input, and outputting a pulsed voltage based on a combination of on and off of these switching elements; A control unit which performs phase shift type PWM control that controls the pulse width of the pulse shape voltage output from the switching circuit by changing the phase of the on / off cycle of each switching element. Provided with When the duty ratio of the pulse shape voltage output from the switching circuit is smaller than the first value, the controller inserts a timing at which all of the plurality of switching elements are turned off in an on / off cycle of the switching element. On the other hand, when the duty ratio is greater than or equal to the first value and smaller than a second value larger than the first value, the timing at which the plurality of switching elements are all turned off is not inserted, and the duty ratio is set to the second value. In this case, the frequency of the on / off cycle is lower than the frequency when the duty ratio is smaller than the second value. Power supply characterized in that. The method of claim 7, wherein And the control unit is configured to control the frequency of the on / off cycle to be lower if the duty ratio is larger than the second value. The method of claim 8, And the control unit is configured to control the frequency of the on / off cycle to be lower when the duty ratio is larger even when the duty ratio is greater than or equal to the first value and smaller than the second value. The method of claim 9, And the control unit is configured to control the frequency of the on / off cycle to be lower when the duty ratio is larger even when the duty ratio is smaller than the first value. The method according to any one of claims 1 to 10, The switching circuit has four switching elements, and these constitute a full bridge circuit. The method of claim 11, And the duty ratio of the on / off cycles of the four switching elements is the same. The method according to any one of claims 1 to 12, The switching element is a MOS FET or an IGBT. The method according to any one of claims 1 to 13, And a boost transformer for boosting the voltage output from the switching circuit. The power supply device according to any one of claims 1 to 14, And a microwave oscillation unit for feeding power from the power supply unit to oscillate microwaves. The method of claim 15, The microwave oscillator A chamber in which the interior is maintained in vacuum, A filament, disposed in the chamber, functioning as a cathode for emitting hot electrons; An anode fed from the power supply device disposed in the chamber to face the filament and forming an electric field between the filament, Magnetic field generating means for forming a magnetic field perpendicular to the electric field outside the chamber Having magnetrons Microwave generator characterized in that. An AC / DC converter that converts an AC voltage into a DC voltage and a plurality of switching elements, and when the DC voltage is input, an ON / OFF cycle occurs in each of the switching elements, and a combination of ON / OFF of each switching element A computer program for causing a computer to function to control a power supply having a switching circuit for outputting a pulse shape voltage based on A phase shift type PWM control for controlling a pulse width of a pulse shape voltage output from the switching circuit by changing a phase of an 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 an on / off cycle of the switching element. A computer program characterized by realizing a computer. An AC / DC converter that converts an AC voltage into a DC voltage and a plurality of switching elements, and when the DC voltage is input, an ON / OFF cycle occurs in each of the switching elements, and a combination of ON / OFF of each switching element A computer program for causing a computer to function to control a power supply having a switching circuit for outputting a pulse shape voltage based on A phase shift type PWM control for controlling a pulse width of a pulse shape voltage output from the switching circuit by changing a phase of an on / off cycle of each switching element; When the duty ratio of the pulse shape voltage output from the switching circuit is smaller than a predetermined value, in the on / off cycle of the switching element, a timing at which all of the plurality of switching elements are turned off is inserted, while the duty ratio is When the predetermined value or more, the function of not inserting the timing at which the plurality of switching elements are all turned off A computer program characterized by realizing a computer. An AC / DC converter for converting an AC voltage into a DC voltage and a plurality of switching elements, when the 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 having a switching circuit for outputting a pulsed voltage based on a combination, A phase shift type PWM control for controlling a pulse width of a pulse shape voltage output from the switching circuit by changing a phase of an on / off cycle of each switching element; When the duty ratio of the pulse shape 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 high, and when the duty ratio is greater than or equal to the predetermined value, the on / off cycle Relatively low frequency capability A computer program characterized by realizing a computer. An AC / DC converter that converts an AC voltage into a DC voltage and a plurality of switching elements, and when the DC voltage is input, an ON / OFF cycle occurs in each of the switching elements, and a combination of ON / OFF of each switching element A computer program for causing a computer to function to control a power supply having a switching circuit for outputting a pulse shape voltage based on A phase shift type PWM control for controlling a pulse width of a pulse shape voltage output from the switching circuit by changing a phase of an on / off cycle of each switching element; When the duty ratio of the pulse shape voltage output from the switching circuit is smaller than the first value, in the on / off cycle of the switching element, a timing at which all of the plurality of switching elements are turned off is inserted, and the duty ratio is set to zero. If the value is greater than or equal to 1 and less than the second value greater than the first value, the timing for turning off the plurality of switching elements is not inserted. If the duty ratio is greater than or equal to the second value, the frequency of the on / off cycle is determined. Lower than the frequency when the duty ratio is less than the second value A computer program characterized by realizing a computer.

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