JPH0695479B2 - Microwave plasma generator - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a microwave plasma generator.

(Prior Art) Low-temperature plasma generated by the discharge of low-pressure gas promotes various chemical reactions while the entire system is at low temperature.
It can be applied to both inorganic and organic materials and has a very wide range of applications, and is used for semiconductor manufacturing processes, polymer materials, surface modification of metals, and the like.

However, in order to generate this low-temperature plasma, the method of exciting by radio waves (13.56MHz) was mainly used in the conventional R & D / practical machines, but using microwaves is more efficient and more efficient. Are known to be advantageous (Hirose: Microwave discharge plasma and its equipment, coating technology, 19, [1], (1980), pages 100 to 105). The advantages are shown below.

The ratio Te / Tg of the electron temperature Te and the gas temperature Tg is large, and a lower temperature plasma can be obtained.

Since no electrode is required, contamination from the electrode can be prevented.

Microwave power can be injected locally, there is no unnecessary radiation loss to the external space, and high-density plasma can be generated.

The oscillator is simple.

There is no radiation loss because microwaves are transmitted through the waveguide,
The structure can be easily adjusted.

By the way, as a conventional plasma generator using microwaves, one having the following structure is known.

Generator / Processing chamber separation type (above document) A well-known structure in which a quartz tube is penetrated into a waveguide to generate plasma in the quartz tube. A processing container is separately provided, and the object to be processed is installed downstream from the plasma.

Metal antenna type (JP-B-57-53858, JP-A-57-9868,
JP-A-56-41382) A method in which a microwave is introduced from a waveguide into another large-capacity processing container by using a metal antenna, and plasma is generated in the processing container.

Periodic structure type (RGBosisio, CFWeissfloch, MRWerth
eimer: The Large Volume Microwave Plasma Generator,
J. Microwave Power, 7 (4), 1972) A microwave is introduced from a waveguide into an open line using a periodic structure to generate plasma in a quartz tube provided below the open line.

(Problems to be Solved by the Invention) However, in the case of the above-mentioned structure, since the plasma generation part is limited by the size of the waveguide, it is impossible to process a large amount of samples or large samples. Further, in this structure, the microwave is largely reflected by the plasma and the efficiency is low.

Also, with the structure of, since it is possible to generate a large number of plasmas in a quartz tube having a relatively large diameter, it is difficult to match the antenna and the waveguide, and the plasma becomes non-uniform. Since it is easy, the device for the improvement becomes complicated.

In addition, the structure of (1) cannot be widened to match the periodic structure type waveguide and the waveguide, and only elongated plasma can be generated (according to the above document, plasma is generated in a quartz glass tube with an outer diameter of 19 mm. In addition, there is a problem that the structure of the line is complicated.

Therefore, in view of the above problems, the present applicant has proposed a microwave plasma processing apparatus equipped with a microwave plasma generator capable of stably generating a large-area and uniform plasma using microwaves with a relatively simple structure. Proposed in Japanese Patent Application No. 60-143036.

The present invention is a further improvement of the microwave plasma generator which is a constituent element of the invention of Japanese Patent Application No. 60-143036 previously proposed by the present applicant.

(Means for Solving Problems) The present invention relates to a microwave oscillator, a waveguide for transmitting a microwave from the microwave oscillator, a dielectric covered line connected to the waveguide, and In a microwave plasma generator provided with a reactor having a microwave introduction window arranged opposite to the dielectric covered line, the microwave is reflected in a space region between the dielectric covered line and the microwave introduction window. It is a microwave plasma generator characterized in that it has a movable reflecting plate for crimping.

Here, the reason why the reflector is movably attached to the dielectric covered line which is a component of the device of the present invention is as follows.

That is, when plasma is generated, the resonance frequency of the dielectric covered line changes, and the microwave that returns from the dielectric covered line toward the microwave oscillator increases. At this time, the resonance frequency is changed by moving the reflector back and forth, and the microwave frequency is 2.45 GHz.
This is because the reflected wave can be made smaller by matching with.

(Operation) Since the present invention is configured to have a movable reflection plate for reflecting microwaves in the space area between the dielectric covered line and the microwave introduction window arranged opposite thereto, The reflection of microwaves can be reduced.

(Example) The present invention will be described below with reference to the accompanying drawings.

In the drawing, reference numeral 1 is a microwave oscillator, from which a microwave of, for example, 2.45 GHz is generated, and a waveguide 2 (WRI
-22,109.22mm × 54.61mm).

Reference numeral 3 is a dielectric covered line communicated with the waveguide 2,
The dielectric layer 4 constituting the dielectric covered line 3 is made of a material having a small dielectric loss such as Teflon, polystyrene or polyethylene. That is, this dielectric layer 4
As a surface wave waveguide brings the concentration of electromagnetic field, and
Since the surface wave is a slow wave slower than the speed of light, microwave energy can be effectively transmitted to the gas to generate plasma.

Further, if the waveguide 2 and the dielectric covered line 3 are separately configured as in this example, the width of the dielectric layer 4 can be made wider than the width of the waveguide 2, so that a large area plasma is generated. Can be made.

Reference numeral 5 denotes a reflecting plate attached to the end of the dielectric covered line 3, which is configured to be movable toward and away from the waveguide 2. That is, by moving the reflection plate 5, the movement of the resonance point after plasma generation is followed, the reflection of microwaves is minimized, the electric field strength is increased, and the efficiency is increased.

Reference numeral 6 denotes a reactor arranged below the dielectric covered line 3, on which a heat resistant material having a small dielectric loss, for example, a quartz glass plate 7 is placed as a microwave introduction window. Through which microwaves are introduced into the reactor 6.

8 is a tilt angle adjusting member disposed below the reactor 6, 9
Is a gas introduction device equipped with a gas cylinder and a flow meter, and 10 is an exhaust device.

Next, a procedure for generating plasma using the device of the present invention will be described below.

First, the reactor 6 is evacuated to a low vacuum or a high vacuum, and a gas is introduced into the reactor 6 in this state.

Next, the microwave oscillator 1 is operated to oscillate microwaves to generate plasma. After that, the reflection plate 5 is moved to minimize the reflection of microwaves.

(Experimental Results) Plasma was generated using the apparatus of the present invention shown in FIG.

In this experiment, a 2.45 GHz microwave oscillator was used.
Teflon having a width of 200 mm, a length of 484 mm and a thickness of 20 mm was used for the dielectric layer.

However, in order not to disturb the electric field distribution by reducing the reflection at the coupling portion between the waveguide and the dielectric coated line, insert a Teflon having a shape as shown in FIG. The Teflon in the track was also tapered over the length of 120 mm as shown in FIG. In FIG. 2, λg represents the wavelength inside the tube, and λ represents the wavelength of the surface wave of the dielectric.

Further, a reflector having a width of 200 mm and a height of 40 mm was used, and a quartz glass plate having a width of 200 mm and a length of 300 mm was used.

In the reactor of the plasma generator of such shape and size,
Air was introduced as the plasma generation gas, gas pressure was 10 Pa, microwave power was 1 KW, the distance between the Teflon and the plasma generation part at the microwave introduction port of the dielectric covered line (left end in Fig. 1) was 60 mm, and the reactor was When the plasma was generated while tilted at 5 °, the plasma was uniformly generated over the entire area of 200 mm × 300 mm.

(Effects of the Invention) As described above, the present invention has a movable reflection plate for reflecting microwaves in the space region between the dielectric covered line and the microwave introduction window. ,
Microwave reflection can be reduced, plasma can be generated over a wide range, and a large amount of processing materials can be processed at once, or a large processing material can be processed. Further, since the device of the present invention can be easily aligned, it has a great effect that the structure and adjustment of the device can be simplified.

[Brief description of drawings]

The drawings show an embodiment of a microwave plasma generator according to the present invention. Fig. 1 (a) is a front view central longitudinal sectional view, (b) is a side view, and Fig. 2 is a waveguide and a dielectric. FIG. 3 is a plan view of the dielectric layer, showing the joint of the body-covered line. 1 is a microwave oscillator, 2 is a waveguide, 3 is a dielectric covered line, 5 is a reflector, 6 is a reactor, and 8 is a tilt angle adjusting member.

Claims (1)

[Claims] 1. A microwave oscillator, a waveguide for transmitting microwaves from the microwave oscillator, a dielectric covered line connected to the waveguide, and a dielectric covered line opposed to the dielectric covered line. In a microwave plasma generator provided with a reactor having a microwave introduction window, a movable reflection plate for reflecting the microwave is provided in a space region between the dielectric covered line and the microwave introduction window. A microwave plasma generator characterized by having.