JPS6299481A - Microwave plasma generator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in microwave plasma generators.

(Prior art) Low-temperature plasma generated by low-pressure gas discharge promotes various chemical reactions even though the entire system is at a low temperature.
It can be applied to both inorganic and organic materials, and has an extremely wide range of applications, including semiconductor manufacturing processes, polymer materials, and surface modification of metals.

However, in order to generate this low-temperature plasma, conventional research and development/practical equipment mainly uses radio waves (13,56 MHz).
However, it is known that using microwaves is more advantageous in terms of efficiency and equipment (Hirose 2 Microwave discharge plasma and its equipment, coating technology, 19 , (1'l, (1980), 100
~105 pages). The advantages are shown below.

(2) The ratio of electron temperature Te to gas temperature Tg is larger than Te/TgA, and a lower temperature plasma can be obtained.

■Since no electrodes are required, contamination from the electrodes can be prevented.

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

■The oscillator is simple.

■There is no radiation loss because microwaves are transmitted through a waveguide.
Integration is possible with a simple structure.

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

■ Separate generation section/processing chamber type (see above) This is a well-known structure in which a quartz tube is passed through a waveguide and plasma is generated inside the quartz tube. Note that the processing container is provided separately, and the object to be processed is placed downstream away from the plasma.

■Metal antenna type (Japanese Patent Publication No. 57-53858, Japanese Patent Publication No. 57-53858,
7-9868, JP-A-56-41382) Microwaves are introduced from a waveguide into another large-capacity processing container using a metal antenna, and plasma is generated within the processing container.

■Periodic structure type (R, G, Bosisio, C, F, W
eissf 1och, M, R, Wertheime
r:The Large Volume Micro
ave Plasma Generator, J, Mi
Crowave T'ower, 7(4), 1972)
Microwaves are introduced into an open line using a periodic structure through a waveguide, and plasma is generated in a quartz tube placed under the open line.

(Problems to be Solved by the Invention) However, in the structure (2) described above, since the plasma generation section is limited by the size of the waveguide, it is not possible to process a large number of samples or large samples. Furthermore, in this structure, the microwaves are reflected by the plasma and the efficiency is low.

In addition, the structure (■) can generate plasma in a relatively large-diameter quartz tube, so it is possible to process a large number of processes, but it is difficult to match the antenna and waveguide, resulting in non-uniform plasma. Because it is easy to cause this, the equipment to improve it becomes complicated.

Furthermore, in the case of the structure (■), due to the matching between the periodic structure type line and the waveguide, it is not possible to create a wide one, and only elongated plasma can be generated (according to the above-mentioned document, plasma is generated in a quartz glass tube with an outer diameter of 19 mm). Furthermore, there is a problem that the structure of the line is complicated.

Therefore, in view of the above-mentioned problems, the present applicant has developed a microwave plasma processing apparatus equipped with a microwave plasma generator that can stably generate large-area, uniform plasma using microwaves with a relatively simple structure. Patent application 1986-1113
It was proposed in issue 036.

The present invention is based on the patent application No. 60-143 previously proposed by the applicant.
This is a further improvement of the microwave plasma generator which is a component of the invention of No. 036.

(Means for Solving the Problems) The present invention provides a microwave oscillator, a waveguide for transmitting microwaves from the microwave oscillator, a dielectric-covered line connected to the waveguide, and a dielectric-coated line connected to the waveguide. A reactor is provided below the covered line, and the dielectric covered line is movably attached with a reflector for reflecting the microwave at its resonant frequency, and the dielectric covered line is movably attached Alternatively, it is a microwave plasma generation device in which at least one of the reactors is configured to be tiltable so that the distance between the two on the repulsion oscillator side becomes narrow.

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

That is, when plasma is generated, the resonant frequency of the dielectric covered line changes, and the microwaves returning from the dielectric covered line to the microwave oscillator become larger. At this time, by moving the reflector back and forth, the resonant frequency is changed, which is 2.45G, which is the frequency of microwaves.
This is because the reflected waves can be made smaller by matching the frequency to Hz.

The reason why at least one of the dielectric covered line or the reactor is configured to be tiltable so that the distance between them on the repulsion oscillator side becomes narrow is as follows.

That is, in the case of not having the configuration as described above, plasma was generated biased toward the oscillator side, and the amount of plasma generated tended to decrease in the direction of propagation of the microwave.

However, with the configuration of the present invention, plasma can be generated uniformly over the entire area.

(Function) The present invention movably attaches a reflecting plate to a dielectric covered line, and at least one of the dielectric coated line or a reactor is arranged so that the distance between the two on the repulsive oscillator side becomes narrower. Since it is configured to be tiltable, reflection of microwaves can be reduced and plasma can be generated uniformly over the entire area.

(Example) The present invention will be explained below based on the accompanying drawings.

In the drawing, l is a microwave oscillator from which, for example, a 2.45 GHz microwave is generated, and a waveguide 2 (WRI-22, 109, 22 x 54.61 dragon)
Transmitted by

3 is a dielectric covered line connected to the waveguide 2;
The dielectric layer 4 constituting the dielectric covered line 3 is made of a material with low dielectric loss, such as Teflon, polystyrene, or polyethylene.

In other words, this dielectric layer 4 serves as a surface wave waveguide to concentrate the electromagnetic field, and since the surface wave is a slow wave slower than the speed of light, it effectively transmits microwave energy to the gas and generates plasma. can be generated.

Furthermore, if the waveguide 2 and the dielectric covered line 3 are configured separately as in this example, the width of the dielectric layer 4 can be made wider compared to the width of the waveguide 2, so a large area of plasma can be generated. can be done.

Reference numeral 5 denotes a reflecting plate attached to the terminal end of the dielectric covered line 3, and is configured to be able to move toward and away from the waveguide 2. That is, by moving this reflector plate 5, it follows the movement of the resonance point after plasma generation, minimizing the reflection of microwaves, increasing the electric field strength, and increasing efficiency.

Reference numeral 6 denotes a reactor disposed below the dielectric covered line 3, and a heat-resistant material with small dielectric loss, such as a quartz glass plate 7, is placed on the upper surface of the reactor, through which microwaves are reacted. It is designed to be introduced into the container 6.

Reference numeral 8 designates an inclination angle adjustment member disposed below the reactor 6 so as to narrow the distance between the reactor 6 and the dielectric covered line 3, which is an example of an anti-microwave oscillator. This is to compensate for the attenuation caused by the loss caused by the plasma and generate plasma uniformly.

Note that, of course, instead of tilting the reactor 6, the dielectric covered line 3 may be tilted, or both may be tilted.

Moreover, instead of slanting these, the thickness of the dielectric layer 4 is made thinner in the direction of propagation of the microwave, and the dielectric layer 4 is made thinner in the direction of propagation of the microwave.
A uniform plasma may be generated by decreasing the degree of coupling between the microwave and the microwave.

9 is a gas introduction device equipped with a gas cylinder and a flow meter, and 10 is an exhaust device.

Next, the procedure for generating plasma using the apparatus of the present invention will be explained below.

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

Next, the microwave oscillator 1 is activated to oscillate a zero microwave wave to generate plasma. Thereafter, the reflection plate 5 is moved to minimize reflection of the microwave.

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

In this experiment, a 2.45GHz microwave oscillator was used,
In addition, the dielectric layer has a width of 200 *** and a length of 484 wm.
, Teflon with a thickness of 200 was used.

However, in order to reduce the reflection at the coupling part between the waveguide and the dielectric-coated line and not disturb the electric field distribution, Teflon with a shape as shown in Figure 2 is inserted into the waveguide, and the dielectric-coated line is The Teflon in the track was also tapered over a length of 12 On as shown in FIG. In FIG. 2, λg represents the tube wavelength, and λ represents the wavelength of the surface wave of the dielectric.

Further, the reflector used was 200 mm wide and 40 mm high, and the quartz glass plate was 200 mm wide and 300 mm long.

In the reactor of the plasma generator with such shape and dimensions,
Air was introduced as plasma generating gas, and the gas pressure was 10 Pa.
, microwave power IKw = 33 The distance between Teflon and the plasma generation part at the microwave inlet part of the electrically coated line (left end in Figure 1) was set to 60 m, and the reactor was tilted 5 degrees to generate plasma. is 200m
300 ** Occurred uniformly over the entire area.

(Effects of the Invention) As explained above, the present invention movably attaches a reflector to a dielectric covered line, and also connects at least one of the dielectric covered line or the reactor to the repulsive oscillator between them. Because it is configured so that it can be tilted so that the interval between the two is narrower, the reflection of microwaves can be reduced, and plasma can be generated uniformly over a wide range, allowing a large amount of processing material to be uniformly processed at once. or process it into
Large-sized processing materials can be processed uniformly. Furthermore, since the device of the present invention can be easily matched, it has great effects such as simplifying the structure and adjustment of the device.

[Brief explanation of drawings]

The drawings show an embodiment of the microwave plasma generator according to the present invention, in which Fig. 1 (a) is a front view and central vertical sectional view, (b) is a side view, and Fig. 2 is a waveguide and dielectric. FIG. 3 is a plan view of the dielectric layer. 1 is a microwave oscillator, 2 is a waveguide, 3 is a dielectric covered line, 5 is a reflection plate, 6 is a reactor, and 8 is an inclination angle adjusting member.

Claims (1)

[Claims] (1) A microwave oscillator, a waveguide that transmits the microwave from the microwave oscillator, a dielectric covered line connected to the waveguide, and a reactor placed below the dielectric covered line A reflector plate for reflecting the microwave at its resonant frequency is movably attached to the dielectric coated line, and at least one of the dielectric coated line or the reactor is attached to the reflector plate for reflecting the microwave at its resonant frequency. A microwave plasma generation device characterized in that it is configured to be tiltable so that the distance between the two on the repulsion oscillator side becomes narrow.