JPH09223597A - Microwave plasma generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent disruption of a vacuum window by detecting discharge so far generated in a waveguide. SOLUTION: A microwave from a microwave generating source is made incident on a waveguide 4, and is introduced into a discharge vessel 1 through waveguides 5 and 6 by passing through a vacuum window 8. Permanent magnets 9 and 10 are arranged on the outer periphery of the discharge vessel 1, and an ion is emitted outside the discharge vessel 1 by extraction electrodes 2 and 3 on which prescribed voltage is impressed. A projecting peeping window 13 capable of monitoring a condition in the waveguide 5 is arranged in the waveguide 5, and a glass window 16 is arranged on its tip, and optical fiber 14 is connected to the glass window 16 through an installing tool 17. A signal from the optical fiber 14 is outputted to a light detector 15, and a signal from the light detector 15 is sent to a microwave generating source, and output of the microwave generating source is controlled. Disruption of the vacuum window 8 is prevented by monitoring discharge in the waveguide 5 by the light detector 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave plasma generator, and more particularly to a microwave plasma generator used as a plasma source for a neutral particle injection device, a plasma dry etching device, a plasma vapor phase growth device and the like. .

[0002]

2. Description of the Related Art A microwave plasma generator is used for a plasma source such as an ion source of a neutral particle injection device for nuclear fusion, a plasma dry etching device used in a semiconductor manufacturing device, a plasma vapor phase growth device and the like. ing. In an apparatus that introduces microwaves of high power of several hundred [W] or more into a discharge vessel to generate plasma, a waveguide that connects a microwave generation source that generates microwaves and the discharge vessel is used. .

The structure of a conventional microwave plasma generator will be described below with reference to the drawings. FIG. 5 is a perspective view of the microwave plasma generator.

Microwaves generated from a microwave generation source (not shown) pass through the waveguide 4 and hit the vacuum window 8.
The inside of the waveguide 4 is in the atmosphere. After passing through the vacuum window 8, the microwave passes through the inside of the L-shaped waveguides 5 and 6. A vacuum atmosphere is formed from the waveguide 5. Atmosphere atmosphere (waveguide 4) and vacuum atmosphere (waveguide 5,
It is divided into 6) and. The vacuum window 8 is made of alumina ceramics.

The microwaves that have passed through the waveguide 6 are
Is introduced into the discharge vessel 1 through a flange 7 connected to the. Permanent magnets 9 and 10 are arranged around the discharge vessel 1. The microwave guided into the discharge vessel 1 ionizes the gas to be discharged, which is previously sealed in the discharge vessel 1, to generate plasma. Ions in the generated plasma are emitted to the outside of the discharge vessel 1 by the extraction electrodes 2 and 3.

The inside of the discharge vessel 1, the inside of the waveguide 5 and the inside of the waveguide 6 have almost the same pressure. The vacuum window 8 is arranged at a position where the plasma generated in the discharge vessel 1 cannot be directly seen.

The operation of the microwave plasma generator configured as above will be described. The gas to be discharged introduced through a gas inlet (not shown) is generated by the permanent magnets 9 and 10 arranged on the outer periphery of the discharge vessel 1 and the waveguides 4 and 5.
Plasma is generated by the interaction with microwaves generated by a microwave generation source (not shown) that passes through and 6. A predetermined voltage is applied to the extraction electrodes 2 and 3 in order to extract desired ions using the generated plasma, and the ions are emitted outside the discharge vessel 1.

[0008]

In the microwave plasma generator having such a structure, since the magnetic field is applied to the inside of the discharge vessel, the discharge is generated more than the inside of the waveguide to which the magnetic field is not applied. The environment is easy to do. Under such an environment, discharge is generated almost in the discharge container during normal operation.

However, the output of the ions emitted from the discharge vessel used for nuclear fusion must be higher than the output conventionally used. Therefore, in order to obtain higher-power ions, it is necessary to generate a higher-density plasma in the discharge vessel. For that purpose, the output of microwaves transmitted by the waveguide is increased or the operating pressure is increased. It was.

However, when such a means is used, the pressure inside the waveguide connecting the vacuum window and the flange is almost the same as the pressure inside the discharge vessel, so there is a risk that discharge will occur inside the waveguide. Will occur.

The problem near the vacuum window at the time of high output will be described with reference to FIG. FIG. 6 is a side view near the vacuum window of the microwave plasma generator. The microwave enters the vacuum window 8 from the direction of the arrow in FIG. The vacuum window 8 is usually composed of alumina ceramics 11 and a metal flange 18. The vacuum window 8 is connected to the waveguide 5 in a vacuum atmosphere, and the waveguide 5 is connected to a discharge container (not shown). The pressure in the waveguide 12 of the waveguide 5 and the pressure in the discharge vessel are substantially the same. Therefore, there is a high possibility that discharge will occur in the waveguide 12. If a discharge occurs in the waveguide 12, the alumina ceramics 11 will be exposed to the impact of plasma particles generated by the discharge and the heat generated by the plasma.

Although not shown in FIG. 6, a water cooling pipe is arranged around the vacuum window 8 against the impact of the plasma particles and the heat generated by the plasma. It is cooling.

However, the cooling of the alumina ceramics 11 with the water-cooled tube has only the ability to cool the heat generated by the passage loss when the microwave passes through the alumina ceramics 11 from the waveguide 4 side. Therefore, when a discharge is generated in the waveguide 12, there arises a problem that the vacuum window 8 (alumina ceramics 11) is broken by the impact of plasma particles, heat generated by plasma, or the like. When the vacuum window 8 is broken, the microwave generation source, the ion source, the vacuum exhaust device that keeps the discharge container and the waveguide in a vacuum state, and the like, which are not shown, are also damaged, resulting in great damage.

In such a conventional microwave plasma generator, in order to avoid the destruction of the vacuum window 8, the operating conditions of the device (for example, setting an upper limit on the output) are limited, or the device is operated by an operator. I was relying on monitoring and skill (experience). Therefore, the amount of plasma density that can be generated is limited, and there is a problem that an operator who constantly monitors the apparatus must exist.

Therefore, the present invention has been made in view of the above problems of the prior art, and detects the discharge generated in the waveguide,
An object of the present invention is to provide a microwave plasma generator that prevents the vacuum window from being destroyed by electric discharge.

[0016]

In order to achieve the above-mentioned object, a microwave plasma generator of the present invention uses a microwave introduced through a waveguide into a discharge vessel in a vacuum atmosphere. In a microwave plasma generator for generating a plasma discharge in a discharge vessel, a detection means for detecting a discharge generated in the waveguide is provided, and an output of a microwave generation source for generating a microwave by a signal from the detection means. Is controlled. Next, the microwave plasma generator of the present invention uses the microwave introduced through the waveguide into the discharge vessel of the vacuum atmosphere,
In a microwave plasma generator for generating a plasma discharge in the discharge vessel, a detection means for detecting light emitted in the waveguide is provided, and a microwave generation source for generating a microwave by a signal from the detection means. The output is controlled.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a first embodiment of a microwave plasma generator, and FIG. 2 is a side view of the microwave plasma generator near the detection means of the first embodiment.

The microwave generated from the microwave generation source 19 enters the waveguide 4 in the atmosphere. The microwave passes through the vacuum window 8 and the waveguide 5 called E corner, and then the waveguide 6 called H corner. The waveguide 5 and the waveguide 6 are connected at a right angle. The waveguide 6 is connected to the discharge vessel 1, and a flange 7 is interposed between the waveguide 6 and the discharge vessel 1. A permanent magnet 9 and a permanent magnet 10 are provided on the outer circumference of the discharge vessel 1.
The microwave guided to the discharge container 1 is emitted to the outside of the discharge container 1 by the extraction electrode 2 and the extraction electrode 3 which are provided in the discharge container 1 and to which a predetermined voltage is applied. Here, the vacuum window 8 is arranged at a position where the plasma generated in the discharge vessel 1 cannot be viewed directly. Since the inside of the waveguide 5 and the inside of the waveguide 6 may be connected to the inside of the discharge vessel 1, the waveguide 5
The inside pressure, the inside of the waveguide 6, and the inside of the discharge vessel 1 have almost the same pressure.

Further, as shown in FIG. 2, the waveguide 5 is provided with a projection-shaped viewing window 13 capable of monitoring the inside of the waveguide 5. The viewing window 13 has a vacuum sealing function. A glass window 16 is provided at the tip of the projection-shaped viewing window 13, and an optical fiber 14 (detection means) provided with an optical sensor or the like is connected to the glass window 16 via a fixture 17. The signal from the optical fiber 14 is output to the photodetector 15 (detection means). The photodetector 15 includes a light receiving element that detects light from the optical fiber 14 and a processing unit that generates a predetermined electric signal according to the amount of light received by the optical fiber 14. The electric signal from the photodetector 15 is sent to a microwave generation source 19 that generates microwaves.

A vacuum window 8 provided between the waveguide 5 in a vacuum atmosphere and the waveguide 4 in an atmospheric atmosphere at substantially the same pressure as that of the discharge vessel 1 is provided in the waveguide 4 and the waveguide 5. It is composed of a metal flange 18 and an alumina ceramics 11 to be connected.

The operation of the microwave plasma generator having the above structure will be described. The discharged gas introduced into the discharge vessel 1 through a gas introduction port (not shown) is a permanent magnet 9 and a permanent magnet 10 arranged on the outer circumference of the discharge vessel 1.
Plasma is generated in the discharge vessel 1 by the interaction between the magnetic field created by and the microwave generated by the microwave generation source 19 that passes through the waveguide 4, the waveguide 5, and the waveguide 6. To do. A predetermined voltage is applied to the extraction electrodes 2 and 3 to extract desired ions to the outside of the discharge vessel 1 by using the generated plasma, and the ions are emitted to the outside of the discharge vessel 1.

At this time, the microwave output must be increased in order to obtain high-density plasma required for nuclear fusion and the like. Then, depending on the plasma generation conditions, discharge also occurs in the waveguides 5, 6 and the like. If discharge is generated in the waveguides 5 and 6, a signal of light generated by discharge is sent to the light receiving element of the photodetector 15 through the optical fiber 14 provided in the viewing window 13. A predetermined signal is sent from the processing unit of the photodetector 15 to the microwave generation source according to the amount of the transmitted light, and the output of the microwave generation source can be controlled. For example, when the processing unit determines that it is necessary to stop the output of the microwave of the microwave generation source due to the amount of light emitted in the waveguide, the stop signal is sent.

In the microwave plasma generator having such a structure, when a discharge is generated in the waveguides 5 and 6, a signal is generated by the photodetector 15 through the optical fiber 14 to generate a microwave. To the microwave source to control the output of the microwave source. Further, if necessary, the output of the microwave generation source can be stopped to stop the discharge. The vacuum window 8 is prevented from being thermally deformed and broken by controlling the output of the microwave generation source. Further, since the breakage of the vacuum window 8 is prevented, at the same time, the safety of peripheral devices (for example, a vacuum device and a discharge container) is improved. Photodetector 1
Since the control by the signal from 5 is sufficiently faster than the speed at which the vacuum window 8 is destroyed by heat, the vacuum window 8 can be protected.

Next, the structure of the second embodiment of the microwave plasma generator will be described with reference to FIG.
In the following embodiments, the same components as those in the first embodiment are denoted by the same reference numerals, and duplicate description will be omitted.

The feature of the second embodiment is that the tip of the optical fiber 14 is inserted into the waveguide 5 so that the light generated by the discharge generated in the waveguide 5 can be detected quickly. FIG. 3 is a cross-sectional view of the vicinity of the viewing window of the second embodiment of the microwave plasma generator. The waveguide 5 is provided with a projection-shaped viewing window 13, and a glass window 16 is attached to the tip of the viewing window 13. The tip of the optical fiber 14 is a glass window 16
And is inserted into the viewing window 13. Optical fiber 1
4 and the viewing window 16 are connected by a fixture 17. The optical fiber 14 is protected by the shield 20.

With such a structure, the discharge generated in the waveguide 5 can be detected more reliably and quickly than in the first embodiment. Then, the reliability in controlling the output of the microwave generation source with respect to the discharge generated in the waveguide 5 is improved as compared with the first embodiment.

As described above, according to the configuration of the present invention, when a discharge is generated in the waveguides 5 and 6, the light emitted by the plasma is automatically detected and the output of the microwave generation source is immediately detected. It is possible to prevent the vacuum window 8 from being broken by controlling (for example, stopping the output of the microwave generation source).

Further, with such a configuration, it is not necessary to constantly monitor the discharge, and it is not necessary to rely on the skill (experience) of the operator. Needless to say, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.

For example, the viewing window does not need to be arranged in parallel with the surface of the alumina ceramics (the position where the alumina ceramics cannot be directly viewed) like the first embodiment, and at least the position where the discharge state in the waveguide can be monitored. If so, it may be placed anywhere. Therefore, as shown in FIG. 4, it is possible to arrange a viewing window at a position facing the surface of the alumina ceramics. Further, the position and the number of viewing windows and optical fibers are not limited to those in the embodiment.

Further, the detecting means is not limited to a photodetector such as an optical sensor, but any detecting means may be used as long as it can detect the state in the waveguide due to the discharge or the like generated in the waveguide. It may be a pressure sensor or an electrostatic probe. If the detection means is an optical sensor, the change in the state of the inside of the waveguide can be detected at the moment when the light emission at the time of discharge occurs inside the waveguide, so that the safety of the device is further improved.

[0031]

According to the microwave plasma generator of the present invention having the above-mentioned structure, it is possible to prevent the destruction of the peripheral equipment such as the vacuum window and the vacuum device from the discharge generated in the waveguide.

[Brief description of drawings]

FIG. 1 is a first microwave plasma generator of the present invention.
Example perspective view

FIG. 2 is a first microwave plasma generator of the present invention.
Side view of the vicinity of the detection means of the embodiment

FIG. 3 is a second microwave plasma generator of the present invention.
Sectional view near the viewing window of the embodiment

FIG. 4 is a side view of the vicinity of the detection means of the microwave plasma generator of the present invention.

FIG. 5 is a perspective view of a conventional microwave plasma generator.

FIG. 6 is a side view near a vacuum window of a conventional microwave plasma generator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge container 2, 3 Extraction electrode 4, 5, 6 Waveguide 7 Flange 8 Vacuum window 9, 10 Permanent magnet 11 Alumina ceramics 12 Waveguide inside 13 Looking window 14 Optical fiber (detection means) 15 Photodetector (detection means) ) 16 glass window 17 fixture 18 metal flange 19 microwave source 20 shield

Claims (3)

[Claims] 1. A microwave plasma generator for generating a plasma discharge in a discharge vessel in a vacuum atmosphere by using a microwave introduced through the waveguide in the discharge vessel. A microwave plasma generator, characterized in that it is provided with a detecting means for detecting a discharge, and the output of a microwave generating source for generating a microwave is controlled by a signal from the detecting means. 2. A microwave plasma generator for generating a plasma discharge in a discharge vessel using a microwave introduced into the discharge vessel in a vacuum atmosphere, wherein light is emitted in the waveguide. A microwave plasma generation device, characterized in that a detection means for detecting the light is provided and the output of a microwave generation source for generating a microwave is controlled by a signal from the detection means. 3. The microwave plasma generator according to claim 1, wherein the detecting means is connected to the waveguide.