JP4528870B1 - Magnetron oscillation apparatus and plasma processing apparatus - Google Patents

Abstract

A magnetron oscillation device and a plasma processing apparatus capable of further stabilizing a transmission frequency are provided.
A frequency detector 7 detects a “shift” from a microwave frequency output from a magnetron 2 and a transmission frequency desired by a user, and generates a shift signal. The drive voltage generator 8 generates and outputs a drive voltage of the impedance generator 5 based on the deviation signal so that the oscillation frequency of the microwave becomes a desired frequency. Thereby, since the oscillation of the magnetron 2 can be controlled, the oscillation frequency can be stabilized in a wide range of output power.
[Selection] Figure 1

Description

  The present invention relates to a magnetron oscillation device using a magnetron as an oscillation tube.

  One of the oscillation devices in the microwave band is a semiconductor oscillation device that uses a transistor as an amplifier. This semiconductor oscillation device is used in a frequency band up to about 1000 MHz. However, in the frequency band of 2450 MHz necessary for plasma generation, the number of usable semiconductor elements is small and expensive, so that the semiconductor oscillation device is very expensive.

Examples of the 2450 MHz band oscillator include a klystron oscillator and a magnetron oscillator. The klystron oscillator is excellent in frequency stability, amplitude controllability, etc., but the klystron is expensive and the price of the power supply for driving the klystron is relatively high. Become.
On the other hand, magnetron oscillators have mass-produced magnetrons up to about 10 kW output power necessary for plasma generation, and can be obtained at low cost. The magnetron drive power supply is simple in construction and can be manufactured at low cost. Therefore, the magnetron oscillation device is frequently used as a power source for generating plasma.

However, the oscillation frequency of the magnetron changes due to variations in load impedance or output power.
A phenomenon in which the oscillation frequency changes depending on the load impedance is called a “pulling phenomenon”.

  In the magnetron, the anode voltage is substantially constant with respect to the anode current, and the output power changes in proportion to the anode current. Also, the oscillation frequency is within the standard value, but changes depending on the anode current.

  Furthermore, the output power of the magnetron can be varied by the anode current. However, when the output power falls below a predetermined value, the oscillation mode jumps and oscillates at a different frequency. This phenomenon in which the oscillation state becomes unstable is called “moding”. Moding can also be caused by changes in heater voltage or load impedance. If moding occurs, intermittent oscillation occurs and the oscillation frequency is not constant, so that the matching circuit connected to the load cannot operate normally. Occurs.

  In order to solve such problems, various proposals have been made for magnetron oscillation devices.

  For example, Patent Document 1 discloses a so-called injection locking system in which a reference signal is injected into a magnetron so that the oscillation frequency of the magnetron is fixed (synchronized) with the frequency of the reference signal and the frequency of the magnetron oscillation device is stabilized. A magnetron oscillation device is disclosed.

  Patent Document 2 discloses an improved injection locking system magnetron oscillation device that injects a reference signal into a magnetron and changes the load impedance of the magnetron using an impedance generator. According to this apparatus, when the load impedance of the magnetron is changed, the oscillation frequency of the magnetron changes based on the pulling phenomenon. Therefore, by adjusting the load impedance using an impedance generator, the oscillation frequency and the frequency of the reference signal are changed. This makes the injection locking operation easy. Therefore, even if the output power of the magnetron is changed, the oscillation frequency is fixed to the frequency of the reference signal, and the output power range in which the oscillation frequency is stable can be widened.

JP 2004-265611 A JP 2006-094214 A

  However, in the above-described injection-locking-type magnetron oscillation device, if the load Q of the magnetron and the injection power of the reference signal generator are constant, the injection locking is released if the anode current of the magnetron is increased to increase the output power. Therefore, it has been difficult to stabilize the frequency.

  In the above-described improved injection locking type magnetron oscillation device, in order to properly operate the impedance generator or the reference signal oscillator, first, the characteristic data of the magnetron and the conditional expression of the injection locking are stored in advance. It is necessary to calculate the load impedance and the injection power that can be synchronized with the detected value of the current or the output current, and output the control signal of the impedance generator or the reference signal oscillator. It is also necessary to store a correspondence table between the anode current and output power of the magnetron and the control signal in advance and output a control signal corresponding to the detected value. For this reason, the processing and the device configuration are complicated.

  Further, in any magnetron oscillation device, it has been difficult to realize cost reduction. That is, in order to perform injection locking easily, an injection power of at least 1/100 of the output power of the magnetron is required. For example, a 10 kW magnetron oscillation apparatus requires an injection power of 100 W. For this reason, the reference signal oscillator requires an amplifier as well as an oscillator, leading to an increase in manufacturing cost.

  Accordingly, a first object of the present invention is to provide a magnetron oscillation device and a plasma processing apparatus that can further stabilize the oscillation frequency.

  It is a second object of the present invention to provide a magnetron oscillation device and a plasma processing apparatus that can stabilize the oscillation frequency with a simpler configuration.

  Furthermore, a third object of the present invention is to provide a magnetron oscillation device and a plasma processing apparatus that can stabilize the oscillation frequency at low cost.

  In order to solve the above-described problems, a magnetron oscillation device according to the present invention adjusts the load susceptance of a magnetron by connecting a magnetron, a launcher that extracts the output power of the magnetron, and an input end to the launcher. An impedance generator, a frequency coupler having an input terminal connected to the impedance generator and extracting a part of the passing power, an input terminal connected to a first output terminal of the frequency coupler, and an oscillation frequency of the magnetron A frequency detection unit that outputs a deviation signal corresponding to a deviation from a predetermined frequency, and an input end connected to the frequency detection unit, an output end connected to an impedance generator, and based on the deviation signal, oscillation of the magnetron Drive voltage generation that generates a drive voltage to make the frequency a predetermined frequency and outputs it to the impedance generator It is characterized in that it comprises and.

  The magnetron oscillation device may further include a non-reciprocal member having an input end connected to the second output end of the frequency coupler and guiding the output power of the magnetron toward the load. Here, the nonreciprocal member may be disposed between the impedance generator and the frequency coupler. Moreover, an isolator, a circulator, etc. are applicable as a nonreciprocal member.

  In the magnetron oscillation device, the impedance generator includes a rectangular waveguide, a ferrite disposed on each of the opposing inner surfaces of the rectangular waveguide, and a rectangular waveguide at a position corresponding to the ferrite. At least one set of a ferrite phase shifter composed of a coil wound around the outer periphery, a short-circuit plate connected to one end of the ferrite phase shifter, and a branching waveguide connected to the other end of the phase shifter You may make it prepare.

The magnetron oscillation device may further include a reference signal supply unit that is connected at one end to the second output terminal of the frequency coupler and supplies a reference signal having a lower power and a stable frequency than the output of the magnetron to the magnetron. May be.
Here, the reference signal supply unit includes a reference signal oscillator that oscillates the reference signal, a nonreciprocal member having one end connected to the output end of the reference signal oscillator, and one end connected to the other end of the nonreciprocal member, A reference signal from the signal oscillator may be guided to the magnetron through the frequency coupler, and a circulator may be provided that guides the output power of the magnetron from the frequency coupler in the direction of the load. Here, the irreversible member may not be used.

  In the magnetron oscillation device, the frequency detection unit includes a split circuit having an input terminal connected to the first output terminal of the frequency coupler, and a phase having a first input terminal connected to the first output terminal of the split circuit. You may make it provide a detection circuit and a phase shift circuit by which the input terminal was connected to the 2nd output terminal of a division circuit, and the output terminal was connected to the 2nd input terminal of a phase detection circuit. Here, a power divider, a 3 dB hybrid, or the like can be applied as the dividing circuit. A balance mixer or the like can be applied as the phase detection circuit. As the phase shift circuit, a delay line, a line stretcher, a resonator, or the like can be applied.

  In the magnetron oscillation device, the frequency detection unit includes a split circuit having an input terminal connected to the first output terminal of the frequency coupler, and a first input terminal connected to the first output terminal of the split circuit. A first detection circuit whose input terminal is connected to the first resonance circuit, a second resonance circuit whose input terminal is connected to the second output terminal of the split circuit, and whose input terminal is the first A second detection circuit connected to the second resonance circuit, and a summing circuit having a first input terminal connected to the first detection circuit and a second input terminal connected to the second detection circuit. You may do it. Here, an LC parallel resonator, a cavity, or the like can be applied as the resonant circuit. An envelope detector or the like can be applied as the detection circuit.

  In the magnetron oscillation device, the magnetron includes at least a cathode that emits electrons by heating, a heater that heats the cathode, and an anode that forms an electric field between the cathode, and the current flowing through the anode increases. You may make it further provide the heater power supply which makes the voltage applied to a heater small.

  The plasma processing apparatus according to the present invention is a plasma processing apparatus that performs a predetermined process on an object to be processed using plasma generated by microwaves, and the magnetron oscillation apparatus is used as a microwave supply source. It is characterized by providing.

  According to the present invention, the frequency detector detects a deviation from a desired oscillation frequency and generates a deviation signal, and the drive voltage generation unit makes the magnetron oscillation frequency a desired frequency based on the deviation signal. By generating the drive voltage and outputting it to the impedance generator, the oscillation of the magnetron can be controlled, so that the oscillation frequency can be stabilized over a wide range of output power.

FIG. 1 is a diagram schematically showing the configuration of the magnetron oscillation device according to the first embodiment of the present invention. FIG. 2A is a cross-sectional view illustrating a configuration example of a reactance stub type impedance generator. FIG. 2B is a cross-sectional view showing a configuration example of a waveguide branch type impedance generator. FIG. 3A is a diagram schematically showing a configuration of an impedance generator in the magnetron oscillation device according to the second exemplary embodiment of the present invention. FIG. 3B is a diagram schematically showing a configuration of an impedance generator in the magnetron oscillation device according to the second exemplary embodiment of the present invention. FIG. 4 is a diagram schematically showing a configuration of a magnetron oscillation device according to the third embodiment of the present invention. FIG. 5 is a diagram schematically illustrating a configuration of a frequency detection unit in the magnetron oscillation device according to the fourth embodiment of the present invention. 6 is a diagram showing the relationship between the phase difference of the microwave at the input end and the output voltage in the balanced mixer of FIG. FIG. 7 is a diagram schematically illustrating a configuration of a frequency detection unit in the magnetron oscillation device according to the fifth embodiment of the present invention. FIG. 8 is a diagram illustrating a relationship between a detection output and an output voltage in the frequency detection unit illustrated in FIG. FIG. 9 is a diagram schematically showing the configuration of the magnetron and the magnetron power supply in the magnetron oscillation device according to the sixth embodiment of the present invention. FIG. 10 is a diagram showing the relationship between the anode current and the heater voltage. FIG. 11 is a diagram schematically showing the configuration of the plasma processing apparatus according to the seventh embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
As shown in FIG. 1, the magnetron oscillation device 1 according to the first embodiment of the present invention includes a magnetron 2, a magnetron power source 3, a launcher 4, an impedance generator 5, a frequency coupler 6, and a frequency. It comprises a detection unit 7, a drive voltage generation unit 8, and an isolator 9.

  The magnetron 2 is an oscillating tube of the magnetron oscillating device 1, oscillates upon receiving power from the magnetron power supply 3, and outputs a microwave. When the magnetron oscillation device 1 is used as a microwave source for plasma generation, for example, a magnetron 2 having an oscillation frequency of 2450 MHz and an output power of several kW to 10 kW can be used.

  The magnetron power source 3 is a power source that supplies voltage and current to the heater and cathode of the magnetron 2. As the magnetron power source 3, it is desirable to use a power source using a switching regulator system with good stability and suppress frequency fluctuations due to power source fluctuations as much as possible.

  The launcher 4 is a high-frequency coupler that efficiently extracts output power from the oscillated magnetron 2 and includes a rectangular waveguide whose one end is short-circuited. The magnetron 2 is provided adjacent to the launcher 4, and an antenna projects into the launcher 4, and radiates microwaves from the antenna.

  The impedance generator 5 has a function of setting the load susceptance of the magnetron 2 to an arbitrary value, and also functions as a standing wave generator. There are many methods for changing the load of the magnetron 2. Moreover, it is classified into a waveguide system, a coaxial system, etc. according to the kind of transmission line used. The impedance generator 5 has one end connected to the output end of the launcher 4 and is used to adjust the load susceptance of the magnetron 2. FIG. 2 shows a configuration example of the waveguide impedance generator 5.

  As shown in FIG. 2A, the reactance stub type impedance generator 5a has a structure in which three stubs 51a, 51b, 51c protrude from the tube wall of the rectangular waveguide 50 into the tube. These stubs 51 a to 51 c are arranged in the direction of the axis Z of the rectangular waveguide 50 at intervals of λg / 8, λg / 4, and the like. “Λg” is the in-tube wavelength of the rectangular waveguide 50. Actuators (not shown) that adjust the length of the rectangular waveguide 50 protruding into the tube are attached to the stubs 51a to 51c in accordance with an input drive signal. The stubs 51a to 51c are made of a metal rod having a circular cross section, and the reactance of the stubs 51a to 51c varies depending on the length of the stubs 51a to 51c protruding into the tube, and the impedance in the rectangular waveguide 50 varies accordingly. To do. The number of stubs may be one or more, but is mainly three. The stub is usually disposed on the H surface of the rectangular waveguide 50, but may be disposed on the E surface.

  FIG. 2B is a cross-sectional view showing a configuration example of a waveguide branch type impedance generator. The impedance generator 5b has a structure in which three branch waveguides 52a, 52b, and 52c are connected perpendicularly to the tube wall of the rectangular waveguide 50. These branching waveguides 52 a to 52 c are arranged in the direction of the axis Z of the rectangular waveguide 50 at intervals of λg / 8, λg / 4, and the like. Each of the branched waveguides 52a to 52c has one end opened in the rectangular waveguide 50, and the other end is electrically short-circuited by the short plates 53a to 53c. Actuators (not shown) for adjusting the positions in the branch waveguides 52a to 52c are attached to the short plates 53a to 53c according to the input drive signal. Thereby, by changing the length from one end to the other end of each of the branched waveguides 52a to 52c, the series reactance is changed, and the impedance in the rectangular waveguide 50 is changed.

  In addition, a combination of a phase shifter and a stub tuner, an impedance generator using a combination of a 3 dB coupler and a variable short circuit, a waveguide four-branch tuner, a slag tuner, etc. are used as the impedance generator 5. Can do. The coaxial impedance generator 5 is obtained by replacing the above-described waveguide rectangular waveguide with a coaxial tube.

  The frequency coupler 6 has a function of extracting part of the passing power, and includes, for example, a directional coupler and a power distributor. The frequency coupler 6 has one end connected to the output end of the impedance generator 5, the first other end connected to the frequency detector 7, and the second other end connected to the isolator 9. As a result, power that is approximately 1/1000000 or less of the output power of the magnetron 2 is extracted and output to the frequency detector 7, and other output power is output to the isolator 9.

  The frequency detector 7 has a function of outputting a DC voltage corresponding to a “deviation” between the oscillation frequency of the magnetron 2 and a predetermined frequency. The frequency detection unit 7 has an output terminal connected to the drive voltage generation unit 8, and outputs a detected DC voltage corresponding to the “deviation” to the drive voltage generation unit 8 as a deviation signal.

  The drive voltage generation unit 8 has a function of processing a shift signal to generate a drive signal for the impedance generator 5, and is configured by, for example, an amplifier. The drive voltage generator 8 has an output terminal connected to the impedance generator 5, and outputs the generated drive signal to the impedance generator 5.

  The isolator 9 has a function of transmitting microwaves in the direction of the load and absorbing microwaves (reflected power) reflected by the load.

  In the magnetron oscillation device 1 having such a configuration, the microwave radiated from the magnetron 2 to the launcher 4 passes through the frequency generator 6 through the impedance generator 5 and is sent from the isolator 9 to the load. At this time, the frequency detector 7 detects a deviation between the oscillation frequency of the magnetron 2 and a desired frequency. When the oscillation frequency of the magnetron 2 deviates from a desired frequency, a deviation signal is generated by the frequency detector 7, and a drive signal for the impedance generator 5 is generated by the drive voltage generator 8 based on this deviation signal. Based on this, the load susceptance of the magnetron 2 is adjusted by the impedance generator 5. Thereby, the oscillation frequency of the microwave output from the magnetron 2 is brought close to a predetermined frequency. As described above, the feedback circuit configured to adjust the load susceptance of the magnetron 2 by the impedance generator 5 according to the degree of deviation between the oscillation frequency of the magnetron 2 and the predetermined frequency desired by the user is provided. Therefore, a frequency control function that tries to bring the oscillation frequency of the magnetron 2 close to a desired frequency always works. Thereby, the oscillation frequency of the magnetron 2 becomes a desired frequency.

  As described above, according to the present embodiment, the frequency detector 7 detects the “deviation” from the microwave frequency output from the magnetron 2 and the oscillation frequency desired by the user, and outputs the deviation signal. The oscillation of the magnetron 2 is controlled by generating and outputting the drive voltage of the impedance generator 5 so that the oscillation frequency of the microwave becomes a desired frequency based on the deviation signal. Therefore, stabilization of the oscillation frequency can be realized in a wide range of output power.

  Further, since the frequency detection unit 7 can be formed of an inexpensive mW class member, it is possible to realize a cost reduction as compared with the case where a reference signal oscillator is used as in the prior art.

  Moreover, since the frequency detection part 7 is comprised with a passive member and does not require electric power, it can suppress a running cost.

  Also, by providing the isolator 9, the reflected power from the load can be absorbed, and malfunction of the feedback circuit can be prevented.

[Second Embodiment]
Next, a second embodiment according to the present invention will be described. In this embodiment, the configuration of the impedance generator is changed from that of the first embodiment. Therefore, in the present embodiment, the same names and symbols are assigned to the same components as those in the first embodiment, and the description thereof is omitted as appropriate.

  In the case of a mechanical drive system in which the impedance generator moves a stub or the like with a motor, a certain operation time is required for the drive. Therefore, a certain time is required to match the oscillation frequency of the magnetron with a desired frequency. Therefore, in the present embodiment, a ferrite phase shifter is used as the impedance generator instead of the mechanical drive type device.

  The ferrite phase shifter is composed of a waveguide, a ferrite disposed on the inner wall surface of the waveguide, and a coil wound around the outer periphery of the waveguide, and a current is passed through the coil. By changing the magnetic field by generating a magnetic field or changing the current flowing in the coil, the magnetic properties of the ferrite, mainly the permeability, is changed to change the wavelength in the high-frequency waveguide, and the phase of the high frequency that propagates Is something that changes. Therefore, in the present embodiment, the drive voltage generation unit 8 generates a current to be output to the coil of the ferrite phase shifter as a drive signal based on the shift signal input from the frequency detection unit 7.

As shown in FIG. 3A, the impedance generator 5c connects a plurality of branch waveguides 54 to form a waveguide path, and at the side of the branch waveguide 54 that forms the waveguide path, One end of the ferrite phase shifter 55 is connected, and the other end of each ferrite phase shifter 55 is short-circuited by the short-circuit plate 56.
The impedance generator 5c of the first example causes high-frequency HF to flow through the waveguide from the magnetron 2 toward the load, and the other end of each ferrite phase shifter 55 in the waveguide. The phase is changed at the point P corresponding to each to change the impedance.

The impedance generator may be configured as shown in FIG. 3B. The impedance generator 5d shown in FIG. 3B connects the branching waveguide 54 and the ferrite phase shifter 55 to form a waveguide path, and before the ferrite phase shifter 55 that configures the waveguide path. One end of a ferrite phase shifter 55 is connected and connected to the side of the connected branching waveguide 54, and a short-circuit plate 56 is provided at the other end of the ferrite phase shifter 55.
The impedance generator 5d of the second example causes a high-frequency HF to flow through the waveguide from the magnetron 2 toward the load, and a point P corresponding to the ferrite phase shifter 55 in the waveguide. The phase is changed by the ferrite phase shifter 55 constituting the waveguide, and the impedance is changed.

  In the impedance generator 5d shown in FIG. 3B, the position of the ferrite phase shifter 55 connected to the side portion of the branching waveguide 54 constituting the waveguide path is determined from the ferrite phase shifter 55 constituting the waveguide path. Is also on the magnetron 2 side, but the position may be on the load side with respect to the ferrite phase shifter 55 constituting the waveguide.

  The impedance generators 5c and 5b can be electrically (electronic) driven while the impedance generator 5 in the first embodiment is mechanically driven. Therefore, the operation speed can be shortened, and the operation time which has been 1 to 2 seconds can be set to 10 to 20 msec. Furthermore, since it is hard to break down, it can be made maintenance-free.

[Third Embodiment]
Next, a third embodiment according to the present invention will be described. The present embodiment is different from the first embodiment in the configuration corresponding to the isolator. Therefore, in the present embodiment, the same names and symbols are assigned to the same components as those in the first embodiment, and the description thereof is omitted as appropriate.

  As shown in FIG. 4, the magnetron oscillation device 10 according to the present embodiment includes a magnetron 2, a magnetron power supply 3, a launcher 4, an impedance generator 5, a frequency coupler 6, a frequency detection unit 7, The driving voltage generation unit 8 and the reference signal supply unit 11 are configured.

  Here, the reference signal supply unit 11 supplies a reference signal to the magnetron 2, and includes at least a reference signal oscillator 12, an irreversible member 13, and a circulator 14.

  The reference signal oscillator 12 is an oscillator that oscillates a reference signal, and an oscillator having an output power lower than that of the magnetron 2 and having a stable oscillation frequency is used. For example, DRO or the like using a crystal oscillator or a dielectric resonator is used as the original oscillation, and amplification and multiplication are performed to obtain output power of several watts to several tens of watts. The oscillation frequency of the reference signal oscillator 12, that is, the frequency of the reference signal is set to a desired frequency that fixes the oscillation frequency of the magnetron 2. For example, when the oscillation frequency of the magnetron 2 is fixed to 2450 MHz, the reference signal of 2450 MHz is used.

  The nonreciprocal member 13 has one end connected to the output end of the reference signal oscillator 12 and the other end connected to one input end of the circulator 14 to transmit the reference signal from the reference signal oscillator 12 to the circulator 14, and vice versa. It is not transmitted in the direction.

  The circulator 14 has one end connected to the output end of the nonreciprocal member 13, guides the reference signal from the reference signal oscillator 12 to the magnetron 2 through the frequency coupler 6, and outputs the output power of the magnetron 2 from the frequency coupler 6. It has a function to guide in the direction of load.

  In this embodiment, a part of the microwave from the magnetron 2 is extracted by the frequency coupler 6, and a deviation between the microwave frequency extracted by the frequency detector 7 and a predetermined frequency is detected to generate a deviation signal. The drive voltage generator 8 generates a drive signal for the impedance generator 5 based on the deviation signal, and the impedance generator 5 adjusts the load susceptance of the magnetron 2 based on the drive signal. A frequency control function that attempts to bring the oscillation frequency closer to the desired frequency is functioning. In such a state, by injecting a reference signal of a desired frequency by the reference signal supply unit 11, the oscillation frequency of the magnetron 2 is always brought close to the reference vibration frequency by the frequency control function, and the range in which the injection locking function works. At the same time, the desired frequency is fixed. As a result, the injection locking function works in the middle of the operation of the frequency control function and is fixed at a desired frequency, so that the time can be further shortened until the oscillation frequency of the magnetron 2 matches the desired frequency.

In the present embodiment, it goes without saying that the impedance generator 5 may be the impedance generators 5c and 5b shown in the second embodiment.
In the present embodiment, the irreversible member 13 may not be provided.
In this embodiment, the input end of the basic signal supply unit 11 is connected to the output end of the frequency coupler 6, but the input end of the reference signal supply unit 11 is connected to the output end of the impedance generator 5. The output end of the signal supply unit 11 may be connected to the input end of the frequency coupler 6.

[Fourth Embodiment]
Next, a fourth embodiment according to the present invention will be described. In this embodiment, the configuration of the frequency detection unit is changed from that of the first embodiment. Therefore, in the present embodiment, the same components as those in the first embodiment are denoted by the same names and reference numerals, and description thereof will be omitted as appropriate.

  As shown in FIG. 5, the frequency detector 7 a includes a power distributor 71, a balanced mixer 72, and a delay line 73.

  The power distributor 71 functions as a dividing circuit, and one output terminal of the frequency coupler 6 is connected thereto. The power distributor 71 has two output ends, one connected to the balanced mixer 72 and the other connected to the delay line 73.

  The balanced mixer 72 functions as a phase detector. This balanced mixer has two input terminals, and the first input terminal is connected to the power distributor 71 and the second input terminal is connected to the delay line 73. The output end of the balanced mixer 72 is connected to the drive voltage generator 8.

  The delay line 73 functions as a phase shift circuit.

  In such a frequency detector 7 a, the microwave (frequency f) input from the frequency coupler 6 is divided into two by the power distributor 71, and one (first path) is the first of the balanced mixer 72. The other (second path) is input to the second input terminal of the balanced mixer 72 via the delay line 73.

  Here, the electrical length L of the delay line 73, the velocity C at which the microwave propagates along the path, and the time difference T that the microwave has to pass through the first path and the second path, respectively, are: It has the relationship shown in the following formula (1).

T = L / C (1)

  From the above equation (1), the microwave phase difference θ between the first input end and the second input end of the balanced mixer 72 is expressed by the following equation (2).

θ = 2πfT = 2πf (L / C) (2)

  When a microwave having a phase difference θ at the input end is input, the output voltage of the balanced mixer 72 is expressed by the following equation (3). In the following equation (3), k is a constant determined by the sensitivity of the balanced mixer 72 and the like, and P is the input power of the microwave.

V _OUT = kP cos θ (3)

From the above equation (3), when the phase difference θ is an odd multiple of π / 2, that is, θ = π / 2, 3π / 2, 5π / 2,..., V _OUT = 0, and V _OUT and θ Is a cos curve as shown by reference symbol a in FIG.

When microwaves of the desired frequency (f ₀₎ is input, so that the output voltage of the frequency detector 7a (balanced mixer 72) is 0V, by setting the electrical length of the delay line 73 (L), the frequency It can be seen that the relationship between the frequency f of the microwave input to the detection unit 7a and the phase difference θ is a proportional relationship as represented by the following equation (4) from the above equation (2). Therefore, the relationship between f and V _OUT is obtained by replacing θ in the above equation (3) with f / K, and becomes a cos curve with the horizontal axis replaced with f in FIG.

f = (1 / 2π) × (C / L) × θ = Kθ (4)
(K = (1 / 2π) × (L / C): constant)

  That is, when a microwave having a frequency shifted from a desired frequency is input, the frequency detection unit 7 a generates a voltage (shift signal) corresponding to the “shift” and inputs the voltage to the drive voltage generation unit 8. . Based on this deviation signal, the drive voltage generator 8 generates a drive signal. By setting the susceptance to a predetermined value by the impedance generator 5 based on this drive signal, a frequency control function for making the oscillation frequency of the magnetron 2 close to a desired frequency works.

  Needless to say, the frequency detector 7 in the third embodiment may be replaced with the frequency detector 7a according to the present embodiment.

[Fifth Embodiment]
Next, a fifth embodiment according to the present invention will be described. In the present embodiment, the configuration of the frequency detection unit is changed from that of the first embodiment, as in the fourth embodiment described above. Therefore, in the present embodiment, the same components as those in the first embodiment are denoted by the same names and reference numerals, and description thereof will be omitted as appropriate.

  As shown in FIG. 7, the frequency detector 7b includes a dividing circuit 74, a first resonance circuit 75, a second resonance circuit 76, a first detection circuit 77, a second detection circuit 78, And an adder circuit 79.

  The dividing circuit 74 divides the input microwave and includes one input end and two output ends. One input terminal of the frequency coupler 6 is connected to the input terminal, and one of the two output terminals is connected to the first resonance circuit 75 and the other is connected to the second resonance circuit 76.

The first resonance circuit 75 resonates with respect to a predetermined frequency (f ₀ + Δf) that is larger than the desired frequency f ₀ by Δf. The output terminal of the first resonance circuit 75 is connected to the first detection circuit 77.

The second resonance circuit 76 resonates with respect to a predetermined frequency (f ₀ −Δf) that is smaller than the desired frequency f ₀ by Δf. The output terminal of the second resonance circuit 76 is connected to the second detection circuit 78.

  The first detection circuit 77 generates a detection output corresponding to the input microwave. The output terminal of the first detection circuit 77 is connected to the addition circuit 79.

  The second detection circuit 78 generates a detection output corresponding to the input microwave. The output terminal of the second detection circuit 78 is connected to the addition circuit 79.

  The adder circuit 79 adds the detection outputs input from the two input terminals. The output terminal of the adder circuit 79 is connected to the drive voltage generator 8.

In such a frequency detecting unit 7b, is input from the frequency coupler 6 microwave (frequency f) is bisected by the dividing circuit 74, while the first resonant circuit resonating with the frequency (f ₀ + Δf) 75 is input to the first detection circuit 77, and the other is input to the second detection circuit 78 via the second resonance circuit 76 that resonates at the frequency (f ₀ −Δf). Assuming that the detection output of the first detection circuit 77 is a positive voltage output V ₊ and the detection output of the second detection circuit 78 is a negative voltage output V ₋ , each has a detection characteristic as shown in FIG.

The detection outputs of the first detection circuit 77 and the second detection circuit 78 are added by the addition circuit 79 and input to the drive voltage generation unit 8. The output power V _OUT of the adder circuit 79 exhibits a characteristic proportional to the deviation from f ₀ as shown in FIG.

Therefore, when the input frequency (f) to the frequency detector 7b is set to a desired frequency (f ₀ ), as described above, when the oscillation frequency of the magnetron 2 is a desired frequency, the output voltage V of the adder circuit 79 is set. _OUT = 0V. On the other hand, when the oscillation frequency of the magnetron 2 deviates from a desired frequency, a voltage (deviation signal) corresponding to the “deviation” is generated in the output voltage V _OUT of the adder circuit 79. When this shift signal is input to the drive voltage generation unit 8, the drive voltage generation unit 8 generates a drive signal based on the shift signal. By setting the load susceptance of the magnetron 2 to a predetermined value by the impedance generator 5 based on this drive signal, a frequency control function for bringing the oscillation frequency of the magnetron 2 closer to a desired frequency works.

  Needless to say, the frequency detector 7 according to the third embodiment may be replaced with the frequency detector 7b according to the present embodiment.

[Sixth Embodiment]
Next, a sixth embodiment according to the present invention will be described. In the present embodiment, the configuration of the magnetron and magnetron power supply is changed from that of the first embodiment. Therefore, in the present embodiment, the same components as those in the first embodiment are denoted by the same names and reference numerals, and description thereof will be omitted as appropriate.

  As shown in FIG. 9, the magnetron 2a includes a heater / cathode H / K in which a cathode and a heater are integrated, and an anode A. Although not shown, the anode A is divided into a plurality of parts, which are connected by a vibration circuit (resonance circuit). A heater / cathode H / K is provided concentrically with the anode A.

A heater power supply 31 of a magnetron power supply 3a is connected to both ends of the heater / cathode H / K. By applying a heater power source to the heater / cathode H / K by the heater power source 31, the heater / cathode H / K is heated and electrons are emitted from the heater / cathode H / K.
An anode power source 32 of a magnetron power source 3a is further connected to one end of the heater / cathode H / K. By applying a negative voltage from the anode power source 32 to the heater / cathode H / K with respect to the anode A connected to the ground, an electric field is formed between the heater / cathode H / K and the anode A. Electrons are emitted from the cathode H / K toward the anode A.
In this state, when a magnetic field is applied parallel to the heater / cathode H / K (perpendicular to the electric field), the microwave M oscillates.

  When the magnetron 2a is operated in this way, among the electrons emitted from the heater / cathode H / K toward the anode A, the electrons returning to the heater / cathode H / K collide with each other. A phenomenon occurs in which H / K is abnormally heated. This phenomenon is called “back heating”. The stronger the oscillation, that is, the higher the output power P, the more intense back heating occurs, and the heater / cathode H / K temperature becomes higher than necessary.

Since the anode current increases in accordance with the output power P of the magnetron 2a, in the present embodiment, the heater voltage is decreased in inverse proportion to the anode current using the heater power supply 31, and the heater / cathode H / K is heated. Suppress.
FIG. 10 is a graph showing the relationship between the anode current and the heater voltage. “Max” represents the upper limit of the heater voltage with respect to the anode current, and “Min” represents the lower limit. According to this graph, back heater can be prevented by controlling the heater voltage using the heater power supply 31.

  Needless to say, the magnetron 2a and the magnetron power supply 3a according to the present embodiment may be applied to the above-described second to fifth embodiments.

[Seventh Embodiment]
Next, a seventh embodiment according to the present invention will be described.
The magnetron oscillation devices 1 and 10 described above can be used as a microwave power source for a plasma processing apparatus. One configuration example of a plasma processing apparatus using the magnetron oscillation devices 1 and 10 is shown in FIG.

The plasma processing apparatus shown in FIG. 11 has a bottomed cylindrical processing container 81 having an open top. A mounting table 83 is fixed to the center of the bottom surface of the processing container 81 via an insulating plate 82. A substrate 84 to be processed is disposed on the upper surface of the mounting table 83.
An exhaust port 85 for evacuation is provided in the peripheral edge of the bottom surface of the processing vessel 81. A gas introduction nozzle 86 for introducing gas into the processing container 81 is provided on the side wall of the processing container 81. For example, when the plasma processing apparatus is used as an etching apparatus, a plasma gas such as Ar and an etching gas such as CF ₄ are introduced from the nozzle 86.

The upper opening of the processing container 81 is closed with a dielectric plate 87. A sealing member 88 such as an O-ring is interposed between the upper surface of the side wall of the processing container 81 and the dielectric plate 87 to ensure airtightness in the processing container 81.
On the dielectric plate 87, a radial line slot antenna (RLSA) 99 which is an antenna of the microwave supply device 90 for supplying the microwave M into the processing container 81 is disposed. The outer peripheries of the RLSA 99 and the dielectric plate 87 are covered with a shield material 89 arranged in an annular shape on the side wall of the processing vessel 81, and the microwave supplied from the RLSA 99 into the processing vessel 81 does not leak to the outside. Yes.

Microwave supply apparatus 90 includes a magnetron oscillator 1, 10 as a microwave power source, the rectangular waveguide 91 in the transmission mode TE _10, the rectangular cylindrical converter for converting a transmission mode from the TE ₁₀ to TE ₁₁ or TM ₀₁ 92, a cylindrical waveguide 93 having a transmission mode of TE ₁₁ or TM ₀₁ , a load matching device 94 provided in the cylindrical waveguide 93, a radial waveguide 95 connected to the cylindrical waveguide 93, RLSA99 formed on the lower surface of the radial waveguide 95.
Here, the radial waveguide 95 includes two circular conductor plates 96 and 97 that are parallel to each other, and a conductor ring 98 that connects and shields the outer peripheral portions of the two conductor plates 96 and 97. A cylindrical waveguide 93 is connected to the central portion of the conductor plate 96 that is the upper surface of the radial waveguide 95. In addition, a plurality of slots are formed in the conductor plate 97 serving as the lower surface of the radial waveguide 95, and the RLSA 99 is configured from these slots.

  In the plasma processing apparatus having such a configuration, when the magnetron oscillation devices 1 and 10 oscillate the microwave M, the microwave M passes through the rectangular waveguide 91, the rectangular cylindrical converter 92, and the cylindrical waveguide 93. Introduced into the radial waveguide 95. The microwave M introduced into the radial waveguide 95 is gradually supplied from the RLSA 99 on the lower surface of the radial waveguide 95 into the processing container 81 while propagating radially from the central portion to the peripheral portion of the radial waveguide 95. Is done. In the processing container 81, the plasma M introduced from the nozzle 86 is ionized by the supplied microwave M to generate plasma P, and the substrate 84 is processed.

Since the magnetron oscillators 1 and 10 use the magnetrons 2 and 2a as oscillation tubes, the magnetron oscillators 1 and 10 can be manufactured at a much lower cost than semiconductor oscillators and klystron oscillators. For this reason, the manufacturing cost of a plasma processing apparatus can be suppressed by using this magnetron oscillation apparatus 1 and 10 as a microwave power supply of a plasma processing apparatus.
In addition, the magnetron oscillation devices 1 and 10 have good frequency stability and no modality, like semiconductor oscillation devices and klystron oscillation devices. For this reason, the operation of the plasma processing apparatus including many frequency-dependent elements can be stabilized and made constant. Further, since it is not necessary to consider the band characteristics, the design of the discharge electrode (radial waveguide 95 and RLSA 99 in the present embodiment) of the plasma processing apparatus becomes easy.

  Magnetron oscillation devices 1 and 10 can also be used in other types of plasma processing apparatuses. For example, it can also be used in an electron cyclotron-resonance (ECR) plasma processing apparatus.

  Needless to say, the second to sixth embodiments may be applied to the present embodiment.

  The present invention can be applied to various apparatuses using microwaves, such as process processing apparatuses, medical accelerators, and communication apparatuses.

  DESCRIPTION OF SYMBOLS 1,10 ... Magnetron oscillation apparatus, 2, 2a ... Magnetron, 3, 3a ... Magnetron power supply, 4 ... Launcher, 5, 5a-5d ... Impedance generator, 6 ... Frequency coupler, 7, 7a, 7b ... Frequency detection part , 8 ... Drive voltage generation unit, 9 ... Isolator, 11 ... Reference signal supply unit, 12 ... Reference signal oscillator, 13 ... Non-reciprocal member, 14 ... Circulator, 50 ... Rectangular waveguide, 51a-51c ... Stub, 52a- 52c ... branch waveguide, 53a-53c ... short plate, 54 ... branch waveguide, 55 ... ferrite phase shifter, 56 ... short circuit plate, 71 ... power distributor, 72 ... balanced mixer, 73 ... delay line, 74: division circuit, 75: first resonance circuit, 76 ... second resonance circuit, 77 ... first detection circuit, 78 ... second detection circuit, 79 ... addition circuit, 81 ... processing vessel, 8 DESCRIPTION OF SYMBOLS ... Insulating plate, 83 ... Mounting base, 84 ... Substrate, 85 ... Exhaust port, 86 ... Gas introduction nozzle, 87 ... Dielectric plate, 88 ... Seal member, 89 ... Shield material, 90 ... Microwave supply device, 91 ... Rectangular waveguide, 92 ... rectangular cylindrical transducer, 93 ... cylindrical waveguide, 94 ... load matching device, 95 ... radial waveguide, 96, 97 ... circular conductor plate, 98 ... ring member, 99 ... radial line slot antenna (RLSA), A ... anode, H / K ... heater / cathode, M ... microwave.

Claims (9)

Magnetron,
A launcher that extracts the output power of this magnetron,
An impedance generator for adjusting the load susceptance of the magnetron, with an input end connected to the launcher,
A frequency coupler in which an input terminal is connected to the impedance generator to extract a part of the passing power;
A frequency detection unit that has an input terminal connected to a first output terminal of a frequency coupler, and outputs a shift signal corresponding to a shift between the oscillation frequency of the magnetron and a predetermined frequency;
An input terminal is connected to the frequency detector, an output terminal is connected to the impedance generator, and a drive voltage for generating the magnetron oscillation frequency at the predetermined frequency is generated based on the deviation signal. A magnetron oscillation device comprising: a drive voltage generation unit that outputs to the impedance generator. The magnetron oscillation device according to claim 1, further comprising a non-reciprocal member that has an input end connected to a second output end of the frequency coupler and guides the output power of the magnetron toward a load. The impedance generator is
A rectangular waveguide, a ferrite disposed on each of the opposed wide inner wall surfaces of the rectangular waveguide, and a coil wound around the outer periphery of the rectangular waveguide at a position corresponding to the ferrite A phase shifter,
A short-circuit plate connected to one end of the phase shifter;
The magnetron oscillation device according to claim 1 or 2, comprising at least one set of branching waveguides connected to the other end of the phase shifter. A reference signal supply unit is provided that has one end connected to the second output terminal of the frequency coupler and supplies a reference signal having a lower power and a stable frequency than the output of the magnetron to the magnetron. The magnetron oscillation apparatus of any one of Claims 1-3. The reference signal supply unit includes:
A reference signal oscillator for oscillating the reference signal;
An irreversible member having one end connected to the output end of the reference signal oscillator;
One end is connected to the other end of the non-reciprocal member to guide the reference signal from the reference signal oscillator to the magnetron through the frequency coupler, and the output power of the magnetron from the frequency coupler is directed to the load The magnetron oscillation device according to claim 4, further comprising: The frequency detector
A split circuit having an input end connected to the first output end of the frequency coupler;
A phase detection circuit having a first input terminal connected to a first output terminal of the divider circuit;
6. The phase shift circuit having an input terminal connected to a second output terminal of the dividing circuit and an output terminal connected to a second input terminal of the phase detection circuit. The magnetron oscillation device according to any one of the above. The frequency detector
A split circuit having an input end connected to the first output end of the frequency coupler;
A first resonant circuit having an input connected to a first output of the divider circuit;
A first detection circuit having an input terminal connected to the first resonance circuit;
A second resonant circuit having an input end connected to a second output end of the divider circuit;
A second detection circuit having an input connected to the second resonance circuit;
The first input terminal is connected to the first detection circuit, and the second input terminal is provided with an addition circuit connected to the second detection circuit. 2. The magnetron oscillation device according to item 1. The magnetron is
A cathode that emits electrons when heated;
A heater for heating the cathode;
And at least an anode that forms an electric field with the cathode,
The magnetron oscillation device according to any one of claims 1 to 7, further comprising a heater power source that decreases a voltage applied to the heater as a current flowing through the anode increases. A plasma processing apparatus that performs predetermined processing on a target object using plasma generated by microwaves,
A plasma processing apparatus comprising the magnetron oscillation device according to claim 1 as a supply source of the microwave.

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