JP2003096570A - Method and apparatus for plasma treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent any ozone from generating in a space surrounded by an annular waveguide and a hollow body. SOLUTION: In a plasma treatment apparatus in which the microwave is fed from the annular waveguide into the hollow body via an opening antenna to generate plasma in the hollow body, a gas feeding means to feed an inert gas, a gaseous nitrogen, or a mixture gas thereof is provided between the annular waveguide and the hollow body. In addition, in a plasma treatment method in which the microwave is fed from the annular waveguide into the hollow body via an aperture antenna of the annular waveguide to generate plasma in the hollow body, the microwave is fed from the aperture antenna of the annular waveguide to a space between the annular waveguide and the hollow body after an inert gas, a gaseous nitrogen, or a mixture gas thereof are provided in the space between the annular waveguide and the hollow body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method and apparatus such as an optical fiber preform manufacturing method and apparatus. INDUSTRIAL APPLICABILITY The present invention is particularly useful for a microwave plasma CVD manufacturing method and apparatus that inputs a large amount of microwave energy at a high temperature.

[0002]

2. Description of the Related Art In a plasma processing method and apparatus, for example, a quartz tube for optical fiber preform whose pressure is reduced is passed through an annular waveguide having a plurality of slot antennas, and microwaves are supplied to the annular waveguide. There is an optical fiber manufacturing method and apparatus in which microwaves are radiated from the slot antenna toward the quartz tube and plasma is generated inside the quartz tube to perform plasma vapor phase growth. The plasma processing method and apparatus are provided with a temperature control means between the annular waveguide and the quartz tube, and the temperature control means includes a heater for supplying the thermal energy necessary for manufacturing the preform of the optical fiber. There is a device that can be used for heat insulation processing such as a heat insulation mechanism (for example, Japanese Unexamined Patent Application Publication No.
01-200369).

However, in the conventional plasma processing method and apparatus, when plasma is generated inside the hollow quartz tube,
In particular, when the microwave power is large, oxygen that absorbs ultraviolet rays, in particular, of the light emitted by the plasma obtains energy and becomes harmful ozone gas. Ozone gas is a harmful gas to the human body and is dangerous when handling the device. Oxygen is usually present because there is air between the annular waveguide and the hollow quartz tube. In addition, in the case of a microwave system that supplies a large amount of power, heat may flow back to the magnetron or the like through the waveguide, and the microwave element such as the magnetron may be damaged.

Further, in a process such as an optical fiber manufacturing apparatus in which a hollow quartz tube has a very high temperature,
Air containing oxygen heated in the hollow quartz tube may oxidize the inside and outside of the annular waveguide. Oxidation of the inner surface of the annular waveguide, particularly the inside of the waveguide through which microwaves propagate, leads to increased propagation loss of microwaves. Therefore, measures against oxidation are important for the performance maintenance of the equipment. In addition, the heat transmitted through the inside of the waveguide may damage the microwave element. In addition, the heated air flows backward in the waveguide, heats the microwave detector and the magnetron, and causes failure of the device. It is necessary to prevent the above structure from being damaged by the heat flow in the waveguide.

In addition to the problem of ozone generation, ultraviolet rays adversely affect human vision. In the case of a device configuration in which the plasma inside the hollow quartz tube can be viewed directly, prevention of ultraviolet rays is an extremely important measure.

[0006]

SUMMARY OF THE INVENTION In view of the above problems, the present invention aims to prevent ozone from being generated in a space surrounded by an annular waveguide and a hollow body, and to prevent a person handling the device from being exposed to ozone. Is the main purpose. A second object of the present invention is to manage the performance of the device by taking measures against oxidation. Another object is to prevent the microwave element from being damaged by the heat transmitted through the inside of the waveguide.

A third object is to prevent the above structure from being damaged by the heat flow in the waveguide. The fourth purpose is to prevent ultraviolet rays so as not to adversely affect human eyesight.

[0008]

A technical means of the present invention for solving this technical problem comprises an annular waveguide having an aperture antenna, and a hollow body inserted inside the annular waveguide. In a plasma processing apparatus in which a microwave is supplied from an annular waveguide through an aperture antenna into a hollow body to generate plasma in the hollow body, an inert gas or nitrogen is provided between the annular waveguide and the hollow body. A gas supply means for supplying the gas or a mixed gas thereof is provided.

According to another technical means of the present invention, the gas supply means supplies an inert gas, a nitrogen gas or a mixed gas thereof between the annular waveguide and the hollow body through an aperture antenna of the annular waveguide. It is configured to be supplied to. Another technical means of the present invention is to prevent the inert gas, the nitrogen gas or a mixed gas thereof supplied between the annular waveguide and the hollow body from escaping to the outside. A shield member is provided to shield the space between the hollow body and the hollow body from the outside.

Another technical means of the present invention is that the hollow body is composed of a substrate having an inner surface coated with a coating. Another technical means of the present invention is that the plasma processing apparatus is an optical fiber manufacturing apparatus for manufacturing an optical fiber preform. Another technical means of the present invention is to supply a microwave from an annular waveguide through an opening antenna of the annular waveguide into the hollow body to generate plasma in the hollow body, in a method of inert gas or nitrogen. A point at which a gas or a mixed gas thereof is supplied between the annular waveguide and the hollow body, and then microwaves are supplied from the aperture antenna of the annular waveguide to the annular waveguide and the hollow body. It is in.

Another technical means of the present invention is to use an inert gas or a nitrogen gas or a mixed gas thereof supplied between the annular waveguide and the hollow body, between the annular waveguide and the hollow body. The point is to fill up. Another technical means of the present invention is
The space between the annular waveguide and the hollow body is shielded from the outside by a shielding member in advance, and an inert gas or nitrogen gas or a mixed gas thereof is provided between the annular waveguide and the hollow body. It is supplied to fill the space between the annular waveguide and the hollow body.

Another technical means of the present invention is that the plasma processing method is an optical fiber manufacturing method for manufacturing an optical fiber preform. Therefore, by flowing the nitrogen gas or the inert gas from the waveguide through the aperture antenna or the like, oxygen existing in the atmosphere can be discharged from the vicinity of the electromagnetic horn or the like. Moreover, since the discharge is not complete, the space between the annular waveguide and the hollow body can be made as closed as possible and the space can be filled with nitrogen gas or inert gas.

Further, by coating the surface of the hollow body with a material that absorbs ultraviolet rays, it is possible to prevent the ultraviolet rays from being emitted to the outside. This technique is particularly useful in an optical fiber manufacturing apparatus among plasma apparatuses.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 show an embodiment in which the present invention is applied to an optical fiber manufacturing apparatus which is one of plasma processing apparatuses. Plasma CVD shown in FIGS.
The apparatus comprises a decompression means 3 for decompressing the hollow part 2 of the quartz tube (hollow body) 1, a gas supply means 4 for supplying a gas to the hollow part 2, and a microwave irradiation from the outer peripheral area of the quartz tube 1. And an annular waveguide 5 for generating plasma of gas in the hollow portion 2 to form a coating on the inner surface of the hollow portion 2.

The quartz tube 1 is made of hollow quartz glass having openings at both ends, and the quartz tube 1 serves as a base material of an optical fiber.
This quartz tube 1 has a diameter of 20 to 60 mm and a length of 2 to 3 m.
Is. The annular waveguide 5 is connected to a microwave oscillating magnetron 7 via an isolator 6 for absorbing reflected microwaves to form a microwave generator. Magnetron 7 is 1 to 10 kW 2.45G
It oscillates a microwave of Hz. The magnetron 7 is provided with a cooling mechanism, and is generally equipped with a water cooling mechanism, but is used with an auxiliary air cooling mechanism for cooling a part of the electric circuit or the magnetron tube.

The isolator 6 absorbs the reflected microwaves with a water load in order to prevent the magnetron 7 from being damaged by the microwaves reflected from the load, and is provided with a water cooling mechanism together with the magnetron 7. There is. The cooling means may be air-cooling, but water-cooling is preferable because the installation space is small and the weight can be reduced. However, in the case of water cooling, when considering moving the isolator 6 and the magnetron 7, it is necessary to move a mechanism such as water cooling, which complicates the device design. Also,
The weight of the cooling mechanism such as water cooling cannot be ignored. In this case, cooling means such as air cooling is also effective, but water cooling is generally used in order to obtain a large magnetron output. The absorption capacity of the isolator 6 is preferably higher than the output of the magnetron 7, but if the reflected power of the load is small, a small capacity may be used in consideration of economic considerations.

The annular waveguide 5 is provided on a moving table 8 similar to a lathe machine. The moving table 8 is provided on the bed 9 so as to be movable in the left-right direction. A waveguide 18, which will be described later, for connecting the annular waveguide 5, the isolator 6, and the magnetron 7 to each other is also installed on the moving table 8. Therefore, it is preferable that these weights are as small as possible because the transfer energy can be reduced. The movable table 8 is movable left and right by a manual handle 10, and is also movable by a driving device such as a motor. It is preferable to control with a personal computer or a sequencer to arbitrarily control the moving speed, moving distance and the like.

That is, the moving table 8 and the like constitute a moving device for the annular waveguide 5. Bed 9
A headstock 11 is fixedly provided at one end of the and a dale stock 12 is provided at the other end of the laterally moving fixed member. A chuck 13 is rotatably supported on the head stock 11, and one end of the quartz tube 1 is detachably attached to the chuck 13. A chuck 14 is also rotatably supported on the dale stock 12, and the other end of the quartz tube 1 of the chuck 14 is detachably attached. Both chucks 13 and 14 are configured to be rotationally driven in synchronization. Chuck 1
The rotation speeds of 3 and 14 are controlled by the controller.

That is, the chucks 13 and 14 constitute a rotating device for the quartz tube 1. The head stock 11 is connected to the gas supply means 4, and the tail stock 12 is connected to the decompression means 3. With both chucks 13 and 14 of the headstock 11 and tailstock 12 holding both ends of the quartz tube 1, the hollow portion 2 of the quartz tube 1 is held.
Is kept airtight from the outside world, and the gas supply means 4
And the pressure reducing means 3 can communicate with each other. In the above description, the gas supply means 4 is connected to the headstock 11 and the pressure reducing means is connected to the tailstock 12,
This can be reversed, and the same effect can be obtained by connecting the pressure reducing means 3 to the head stock 11 and the gas supply means 4 to the tail stock 12.

The depressurizing means 3 is composed of a vacuum pump and holds the pressure in the hollow portion 2 of the quartz tube 1 under reduced pressure. Gases that corrode metals, such as chlorine-based gas, may be used, so it is advisable to make a selection in consideration of measures against corrosion. The gas supply means 4 supplies a raw material gas required according to the coating film formed on the inner surface of the hollow portion 2 of the quartz tube 1. For example, SiCl ₄ + O ₂ , SiCl ₄ + GeCl ₄ +
A gas such as O ₂ or SiCl ₄ + O ₂ + C ₂ F ₆ is supplied.

The two chucks 1 are mounted on the bed 9.
A furnace device 15 is provided so as to cover the quartz tube 1 and the annular waveguide 5 which are held by 3, 14. This furnace device 1
Reference numeral 5 has a lid body that can be opened and closed, and the quartz tube 1 can be removed by opening the lid body. Figure 3-
As shown in FIG. 5, in the annular waveguide 5, aperture antennas 17 that form slot antennas are arranged at equal intervals in the circumferential direction at four locations on the inner surface of the waveguide 5. The aperture antenna 17 is provided on the inner peripheral surface of the annular waveguide 5.
The quartz tube 1 has an opening hole that is opened parallel to the axis of the quartz tube 1. The quartz tube 1 is inserted inside the annular waveguide 5, and a space 32 is formed between the annular waveguide 5 and the quartz tube 1.
Microwaves are radiated from the aperture antenna 17 toward the quartz tube 1. At this time, microwaves pass through the space 32 between the annular waveguide 5 and the quartz tube 1.

The microwave of 2.45 GH ₂ sent through the magnetron 7 and the isolator 6 is the waveguide 1
It propagates through 8 to the coupling antenna 19. The microwave power is 1 to 10 kW. The coupling antenna 19 is installed for the purpose of electromagnetically coupling the waveguide 18 and the annular waveguide 5, and a metal rod made of a material having good electrical conductivity is used as the waveguide 18 and the annular waveguide 5. It is installed in a form that penetrates between. The insertion depth of the coupling antenna 19 can be changed manually or automatically so that the coupling state of the microwave in the waveguide 18 and the microwave in the annular waveguide 5 can be arbitrarily changed. It has become.

The waveguide 18 is generally made of a material such as aluminum. Any material can be used as long as it has a low electric resistance on the surface, and silver is an excellent material, but it is expensive and not economical. Therefore, the waveguide 18 is made of aluminum,
Alternatively, it is preferable to use stainless steel. Parts made of stainless steel may be plated with silver to reduce the electric resistance on the surface. A microwave transmission window 22 such as quartz or ceramics, through which microwaves are transmitted but air is mechanically blocked, is provided at one or a plurality of portions of the waveguide 18.

The microwave transmission window 22 is intended to keep the inside of the waveguide 18 airtight and shut off the air flow between the load side and the microwave oscillator (magnetron 7) side. The microwave transmission window 22 is preferably made of a material having a small dielectric loss, such as quartz or ceramic, which hardly absorbs microwaves. Thereby, the microwave passes through the inside of the waveguide 18, but the air flow is blocked by the microwave transmission window 22 and does not pass through. In the present embodiment, a movable plunger tuner 20 that terminates with a conductive metal is provided for matching microwaves. The position of the movable plunger tuner 20 can be changed manually or automatically. It should be noted that the variable position range of the movable plunger tuner 20 may be at least half the guide wavelength of the microwave. Microwaves are matched by the movable plunger tuner 20 and the coupling antenna 19. The matching state of the microwave can be confirmed by the microwave power output from the magnetron 7 and the microwave power returned to the isolator 6. It is shown that the smaller the reflected power is, the better the matching is compared with the output power of the microwave. It is preferable to measure the electric power of the traveling wave and the reflected wave of the microwave with the crystal detector (detection unit) 23 shown in FIG. 3 or the like, but the traveling wave power should be estimated from the electric power supplied to the magnetron 7. With respect to the reflected wave power, almost the same result can be obtained by measuring the power supplied to the isolator 6.

If matching is obtained and sufficient microwave power is output, the microwave is supplied to the gas in the quartz tube 1 and the plasma 21 is obtained if various conditions such as pressure and gas species are adjusted.
Occurs, the desired chemical change proceeds, and the film volume can be realized. The crystal detector 23 has a function of measuring electric power passing through the crystal detector 23.
The measured power has directionality, and the traveling wave (microwave power from the magnetron 7 to the load) and the reflected wave (power returning from the load to the magnetron 7) can be measured independently. For example, two crystal detectors 23 having the above-mentioned directivity are installed, one for measuring traveling wave power and the other for measuring reflected power.

The isolator 6 and the ring-shaped waveguide 5 are connected by a waveguide 18 so that microwaves are transmitted to the isolator 6.
The gas is supplied to the annular waveguide 18 from the gas pipe 2. On the other hand, for example, the gas pipe 2 that can introduce gas into the waveguide 18
Install 5. The position where the gas pipe 25 is connected is the waveguide 1
8 is connected to the isolator 6 and the magnetron 7, and the waveguide 18 is passed through the isolator 6 and the magnetron 7.
The gas may be allowed to flow. A valve 27 that can adjust the gas flow rate is provided in the middle of the gas pipe 25. With this, the flow rate of the gas flowing into the waveguide 18 is adjusted. The valve 27 may be a manual valve or may be automatically controlled by a so-called mass flow controller.

An inert gas, nitrogen gas or a mixed gas thereof is supplied from a gas cylinder 29. If necessary,
A pressure reducing function such as a pressure reducing valve may be provided. The gas flowing through the gas cylinder 29, the gas pipe 25, and the valve 27 is supplied to the annular waveguide 5 through the waveguide 18, and further through the opening antenna 17 of the annular waveguide 5, the annular waveguide 5 and the hollow body 1. Supplied during. Therefore, by the gas cylinder 29, the gas pipe 25, the valve 27, etc.,
Between the annular waveguide 5 and the hollow body (quartz tube) 1, a gas supply means 30 for supplying an inert gas, a nitrogen gas, or a mixed gas thereof is configured.

The mounting position of the gas supply means 30 is shown in FIG.
Although it is installed in the waveguide 18, it may be installed in the isolator 6 or the crystal detector 23 as long as it is finally supplied to the waveguide 18. In this case, the microwave transmission window 22 is installed closer to the magnetron 7 than the connecting portion of the gas supply means 30 so that the gas delivered from the gas supply means 30 flows to the load side. The gas supplied from the gas supply means 30 is preferably a chemically stable gas, and may be an inert gas such as argon or helium, or a gas such as nitrogen.

The gas delivered from the gas supply means 30 is blocked by the microwave transmission window 22 and does not proceed to the magnetron 7 side, but passes through the inside of the waveguide 18 and the hole 31 through which the coupling antenna 19 is passed. Is supplied to the inside of the annular waveguide 5. The microwave penetrates the space 32 and the quartz tube 1 to generate plasma 21 inside the quartz tube 1. Generally, the plasma 21 emits light in a wide band and also has a short wavelength component. Often has UV components,
When the plasma emission intensity is high, energy for exciting the gas is applied in the space 32.

If an inert gas is not supplied from the gas supply means 30, since an atmosphere containing oxygen is usually present in the space 32, the oxygen atoms excited by the ultraviolet rays are combined to generate ozone. . However, in this embodiment, an inert gas, a nitrogen gas, or a mixed gas thereof is supplied between the annular waveguide 5 and the quartz tube (hollow body) 1 so that the inert gas, the nitrogen gas, or the nitrogen gas is supplied. After filling the space between the annular waveguide 5 and the quartz tube 1 with these mixed gases, microwaves are passed through the aperture antenna 1 of the annular waveguide 5.
7 is supplied between the annular waveguide 5 and the quartz tube 1, and plasma is generated in the quartz tube 1. Therefore, when the plasma 21 is generated, the inert gas or the nitrogen gas or these gases is emitted from the annular waveguide 5. Since the mixed gas is supplied to the space 32 through the opening antenna 17 and is filled therewith, it is possible to suppress the generation of ozone as described above to an extremely low level. Since argon and helium are extremely stable gases, they rarely undergo chemical changes, and nitrogen is also a stable gas, so it is difficult to generate harmful gas. If the gas does not contain oxygen, ozone will not be generated. It is also an advantage that the plasma source including the annular waveguide 5 can be cooled by flowing the gas.

FIG. 6 shows another embodiment, in which the gas supply means 30 is installed in the magnetron 7, and an inert gas or nitrogen gas is finally supplied from the magnetron 7 to the waveguide 18 through the isolator 6 and the detector 23. I am trying to do it. The microwave transmission window 22 is omitted because it is unnecessary. The other points are the same as in the case of the embodiment of FIGS. 7 and 8 show another embodiment, in which the plurality of aperture antennas 17 of the annular waveguide 5 are constituted by electromagnetic horn antennas. That is, in the embodiment of FIGS.
Is a slot antenna, but the aperture antenna 1
Since 7 may have a structure capable of obtaining a flow of airflow between the annular waveguide 5 and the space 32, the aperture antenna 17 is composed of an electromagnetic horn antenna instead of the slot antenna. Electromagnetic horn antennas (aperture antennas) 17 are arranged at four locations on the inner surface of the waveguide 5 at equal intervals in the circumferential direction. This aperture antenna 17 is
On the inner peripheral surface of the annular waveguide 5, a pyramidal electromagnetic horn opened parallel to the axis of the quartz tube 1 is formed. The electromagnetic horn antennas shown in FIGS. 7 and 8 are better in that the antenna matching is excellent. In addition, in this embodiment, the hollow body 1 is
It is composed of a cylindrical substrate (hollow substrate) whose inner surface is coated with a coating. Microwave antenna 1
It radiates from 7 toward the hollow body (hollow substrate) 1. At this time, microwaves pass through the space 32 between the annular waveguide 5 and the hollow body 1. The other points are the same as those of the embodiment of FIGS. 1 to 5 or the embodiment of FIG.

9 and 10 show another embodiment,
Shielding members 37a and 37b for closing both axial ends of the space 32 between the annular waveguide 5 and the hollow body 1 are provided.
A slight air discharge gap 38 is provided between 37b and the hollow body 1. The other points are the same as those of the embodiment of FIGS. 1 to 5 or the embodiment of FIG. In this case, the space 32 between the annular waveguide 5 and the hollow body 1 is almost filled with the gas supplied from the gas supply means 30. As in the case of the embodiment of FIGS. 1 to 5 or the embodiment of FIG. 6, without the shielding members 37a and 37b, the gas supplied from the aperture antenna 17 flows from the space 32 in the longitudinal direction of the hollow body 1. It is easily discharged toward the outside and can be easily exchanged with the outside air. Therefore, in order to fill the space 32 with a gas component that does not generate ozone or the like, it is necessary to flow a large amount of gas supplied from the gas supply hand throw 30, which is uneconomical. But,
In this case, if the shielding members 37a and 37b are provided and a slight air discharge gap 38 is provided, the shielding members 37a and 37b are provided.
The space 32 between the annular waveguide 5 and the hollow body 1 is shielded from the outside, and the inert gas or nitrogen gas supplied between the annular waveguide 5 and the hollow body 1 or a mixed gas thereof is supplied. Can be prevented from escaping to the outside, and the space 32 is almost filled with the gas supplied from the gas supply means 30. As a result, the gas inside the space 32 can be prevented from mixing with the outside air, and the generation of harmful gases such as ozone can be minimized.

11 and 12 show another embodiment, in which the hollow body 1 is covered with a cylinder 39, such as ceramic, which is opaque to ultraviolet rays and has a good microwave transparency, and the cylinder 3
An inert gas is sealed between the hollow space 9 and the hollow body 1 by a gas supply means 30 (not shown). The other points are the same as those of the embodiment of FIGS. 1 to 5 or the embodiment of FIG. In this case, the microwave radiated from the annular waveguide 5 passes through the cylinder 39 and reaches the inside of the hollow body 1 to generate the plasma 21. Since the ultraviolet rays emitted from the plasma 21 are not emitted to the outside of the cylinder 39, they are absorbed and attenuated inside the cylinder 39. Since the inside of the cylinder 39 is filled with an inert gas, no harmful gas is generated. In this structure, not only harmful gas is not generated, but also the surface cleanliness of the hollow body 1 is maintained. Although a method of covering the entire apparatus with a container and filling it with an inert gas is conceivable, it is economically inferior to the case of the above-described embodiment.

If the space 32 cannot be kept airtight, such as when the diameter of the hollow body 1 changes, coating the surface of the hollow body 1 with a material that absorbs ultraviolet rays will also generate harmful gases such as ozone. Can be suppressed. In this case, it goes without saying that the ultraviolet absorbing material must withstand the use environment. In addition, in the above-described embodiment, the gas supply unit 30 supplies the inert gas or the nitrogen gas to the annular waveguide 5.
The gas is supplied to the space 32 side between the hollow body 1 and the hollow body 1, but instead of this, the gas to be supplied is not limited to the inert gas or the nitrogen gas, and for example, a mixed gas of the inert gas and the nitrogen gas is mixed. The gas may be supplied to the space 32 side.

[0035]

According to the present invention, ozone can be prevented from being generated in the space surrounded by the annular waveguide and the hollow body, and the person handling the device can be prevented from being exposed to ozone. In addition, the performance of the device can be maintained and managed by taking measures against oxidation. In addition, it is possible to prevent the microwave element from being damaged by the heat transmitted through the inside of the waveguide. Further, it is possible to prevent the above-mentioned structural body from being damaged by the heat flow in the waveguide. Further, it is possible to prevent ultraviolet rays so as not to adversely affect human eyesight.

[Brief description of drawings]

FIG. 1 is a side view of an entire apparatus showing an embodiment of the present invention.

FIG. 2 is a front view of the same.

FIG. 3 is a front sectional view of the waveguide and the annular waveguide portion.

FIG. 4 is a side sectional view of the annular waveguide and the hollow body portion.

FIG. 5 is a front sectional view of the annular waveguide and the hollow body portion.

FIG. 6 is a schematic front cross-sectional view of a waveguide and an annular waveguide portion showing another embodiment.

FIG. 7 is a side sectional view of an annular waveguide and a hollow body portion according to another embodiment.

FIG. 8 is a front sectional view of the annular waveguide and the hollow body portion.

FIG. 9 is a side cross-sectional view of an annular waveguide and a hollow body portion showing another embodiment.

FIG. 10 is a front sectional view of the annular waveguide and the hollow body portion.

FIG. 11 is a side sectional view of an annular waveguide and a hollow body portion showing another embodiment.

FIG. 12 is a front sectional view of the annular waveguide and the hollow body portion.

[Explanation of symbols] 2 Quartz tube (hollow body) 5 Ring waveguide 17 aperture antenna 18 Waveguide 21 plasma 30 gas supply means 32 spaces 17a shielding member 17b Shielding member

Claims (9)

[Claims] 1. A hollow body comprising an annular waveguide having an aperture antenna and a hollow body inserted inside the annular waveguide, wherein microwaves are supplied from the annular waveguide into the hollow body through the aperture antenna. In the plasma processing apparatus adapted to generate plasma, a gas supply means for supplying an inert gas or a nitrogen gas or a mixed gas thereof is provided between the annular waveguide and the hollow body. Characteristic plasma processing device. 2. The gas supply means is configured to supply an inert gas, a nitrogen gas or a mixed gas thereof between the annular waveguide and the hollow body through the aperture antenna of the annular waveguide. The plasma processing apparatus according to claim 1, wherein: 3. In order to prevent the inert gas or the nitrogen gas or the mixed gas thereof supplied between the annular waveguide and the hollow body from escaping to the outside, the annular waveguide and the hollow body are separated from each other. The plasma processing apparatus according to claim 1, further comprising a shielding member that shields the space between the outside and the outside. 4. The plasma processing apparatus according to claim 1, wherein the hollow body is composed of a substrate having an inner surface coated with a coating film. 5. The plasma processing apparatus according to any one of claims 1 to 4, which is an optical fiber manufacturing apparatus for manufacturing an optical fiber preform. 6. A plasma processing method in which microwaves are supplied from an annular waveguide through an aperture antenna of the annular waveguide into a hollow body to generate plasma in the hollow body, wherein an inert gas or nitrogen gas or a mixture thereof is used. Gas is supplied between the annular waveguide and the hollow body, and then microwaves are supplied from the aperture antenna of the annular waveguide between the annular waveguide and the hollow body. Processing method. 7. The space between the annular waveguide and the hollow body is filled with an inert gas, a nitrogen gas or a mixed gas thereof supplied between the annular waveguide and the hollow body. The plasma processing method according to claim 6. 8. A space between the annular waveguide and the hollow body is shielded from the outside by a shielding member in advance, and an inert gas, a nitrogen gas, or a mixed gas thereof is filled with the annular waveguide and the hollow body. The plasma processing method according to claim 7, wherein the plasma processing method is performed by supplying the space between the annular waveguide and the hollow body so as to fill the space between the annular waveguide and the hollow body. 9. The plasma processing method according to claim 6, wherein the plasma processing method is an optical fiber manufacturing method for manufacturing an optical fiber preform.