JPS635524A - Microwave plasma generating device - Google Patents

Abstract

PURPOSE:To minimize the loss in microwave supply power consumption by a method wherein an even number exceeding at least two each of passive reflectors are provided in waveguides almost in parallel with each other at an interval equivalent to 1/4 of the wavelength in the microwave guide. CONSTITUTION:An even number exceeding at least two each of passive reflectors 6a, 6b reflecting microwaves are provided in waveguides 7, 13 opposing to a discharge region 14 while the passive reflectors 6a, 6h are almost in parallel with each other at an interval equivalent to 1/4 of the wavelength in the microwave guide. At this time, considering the microwaves proceeding in the incident direction out of the waves reflected by the passive reflectors 6a, 6b, the path difference between the reflected waves due to the first passive reflector 6a and the one due to the second passive reflector 6b is 1/2 of the guide wavelength while a return trip is made, and consequently is Shifted by 180 degrees making the reflected waves cancel each other. Resultantly, the returning waves in the incident direction are reduced to minimize the loss in power consumption. Furthermore, the microwaves are irregularly reflected to expand the plasma producing space.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is used in microwave plasma etching, etc.
The present invention relates to a microwave plasma generator that efficiently generates large-diameter plasma.

BACKGROUND OF THE INVENTION In recent years, plasmas excited by microwaves (e.g. 2.45 GHz) are being used for plasma processing (e.g. dry etching) of semiconductor wafers. ) This is because the plasma density is higher than that of electric discharge, and since it is an electrodeless discharge, high-speed, low-damage plasma processing is expected.

An example of the conventional microwave plasma generator mentioned above will be described below with reference to the drawings.

FIG. 6 shows the main structure of a conventional microwave plasma generator. In FIG. 4, 1.degree.2 is a waveguide, which transmits microwaves.

Reference numeral 3 denotes a conductor, which transmits microwaves and maintains a vacuum in the discharge region 5. 4 is a sample.

The operation of the microwave plasma generator configured as described above will be described below.

First, the microwave that has propagated through the waveguide 1 is transferred to the waveguide 2.
and is transmitted through the conductor 3 to the discharge region 6.

The tube wall of the waveguide 2 is oblique to the axis of the waveguide 1 in order to efficiently reflect and scatter microwaves.

Problems to be Solved by the Invention However, in the above configuration, when the microwaves emitted from the waveguide 1 are reflected and scattered by the wall of the waveguide 2, the axial direction of the waveguide 1 Since there is a reflected wave that propagates to the discharge region, there is a problem in that the efficiency of introducing microwave power into the discharge region becomes poor.

In view of the above problems, the present invention provides a microwave plasma generation method that increases the efficiency of introducing microwaves into a discharge region.

Means for Solving the Problems In order to solve the above problems, the microwave plasma generator of the present invention includes at least two reflecting plates in the waveguide that face the discharge area and reflect microwaves. An even number of reflecting plates are provided, and the reflecting plates are substantially parallel to each other, and the distance between them is equal to the wavelength within the microwave tube.

Function The present invention has the above-described configuration, and considering the microwaves traveling in the direction of the incident wave among the reflected waves reflected by the reflecting plate, the reflected waves by the first reflecting plate and the reflected waves by the second reflecting plate are as follows. Since the path difference is just different in the tube wavelength during the round trip, the phase shifts by 180 degrees, and as a result, the reflected waves cancel each other out.

Therefore, there are fewer waves returning in the direction of the incident wave, and power loss is reduced.

EXAMPLE Hereinafter, a microwave plasma generator according to an example of the present invention will be described with reference to the drawings.

FIGS. 1 and 2 show the structure of a microwave reflecting section provided within a waveguide of a microwave plasma generator according to a first embodiment of the present invention.

In Figures 1 and 2, 6a and 6b are reflecting plates made of a material that reflects microwaves (for example, a metal with high electrical conductivity), and are directed in the direction of the microwave incident wave (horizontal direction in Figure 1). ) is above the wavelength in the microwave tube, 7 is the waveguide, 8 is the bolt erected on the waveguide, 9 is above the wavelength in the microwave tube.
is a support for moving the reflection plates ea and eb from the outside, and by operating the support 9, the reflection plates 6a and 6b are moved.
The inclination is changed while keeping the two parallel to each other. 1o is a lock nut that holds the support body 9. The operation of the microwave brass generator configured as described above will be described below with reference to FIGS. 1 and 2.

FIG. 2 shows the waveguide terminal end and discharge section of the microwave plasma generator of the present invention.

11 is a dielectric through which microwaves pass, 12 is a sample, 13 is a waveguide, and 14 is a discharge region within the vacuum container 30. The microwave transmitted through the waveguide 13 passes through the reflection plate 6
The light is reflected and scattered by elements a and 6b, passes through the dielectric 11, and generates plasma in the discharge region 14. At this time, as shown in FIG. 1, the interval P between the reflection plates 8a and 6b in the direction of the microwave incident wave is 7, which is the wavelength within the microwave tube. The amount of reflected waves returning in the wave direction is reduced. Furthermore, when the support body 9 is moved up and down, the inclinations of the reflectors ea and eb change, but they remain parallel, so the distance P between the reflectors 6a and 6b remains at 7, which is the wavelength within the microwave tube. Therefore, as mentioned above, with the microwave return reduced, the reflector ea
, eb angle can be changed.

As described above, according to this embodiment, the microwave reflector 6
By installing two panels a and 6b separated by 7, which is the wavelength within the tube, and allowing the reflectors above to move a distance t while maintaining parallelism,
Microwaves can be reflected and scattered while reducing the loss of microwave supplied power. As a result, the area of generated plasma can be increased.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a diagram showing the configuration of a microwave reflecting section of a microwave plasma generator showing a second embodiment of the present invention.

In the same figure, 15a, 15b, 15c.

15d is a microwave reflector whose basic configuration is the same as that shown in FIG.

The difference from the configuration shown in FIG. 1 is that a drive belt 17.degree. 18, pulleys 19a, 19b, 19c, and a drive motor 20 are provided to rotate the reflecting plates 15a to 15d at the same rotational speed.

The operation of the microwave plasma generator configured as described above will be described below.

First, with the reflectors 15a and 15c and 16b and 15d parallel to each other, when the reflectors 16a to 16d are synchronously rotated using the drive bell (17, 113° pulleys 19a, 1sb, 19c, and motor 20), Each reflector can be rotated while remaining parallel.

Therefore, a rotating mechanism can be added to the reflecting section while reducing the loss of microwave power.

As described above, drive bell) 17, 18 and pulley 19a
, 19b, 19c and the motor 2o so that the reflector rotates at the same rotation speed, a rotation mechanism can be introduced to the reflector, and the reflection and scattering of microwaves can be made even more uniform. .

In the embodiment of the present invention, the reflecting plates are parallel, but for example, as shown in FIGS. 4 and 6, the reflecting plates 21 a
, 21b, 22a, and 22b are made into curved surfaces to change the microwave reflection/scattering effect from that of flat plates, the effect of reducing microwave power loss can be maintained.

Effects of the Invention As described above, the present invention provides at least two or more even number of reflecting plates in a waveguide, and configures them so that they are substantially parallel and the distance between them is equal to the wavelength within the microwave tube. As a result, it is possible to reduce the loss of microwave supply power, reflect and scatter microwaves, and obtain plasma over a large area.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the configuration of a microwave reflection section of a microwave plasma generator according to a first embodiment of the present invention;
Fig. 2 is a cross-sectional view showing the entire structure, and Fig. 3 is a cross-sectional view showing the second embodiment of the present invention.
FIG. 4 and FIG. 6 are cross-sectional views showing a modified form of the microwave reflecting section, and FIG. 6 is a conventional microwave plasma generating device. FIG. 6a, 8b...Reflector, end, 13...
Waveguide, 14... Discharge area, 15 a, 1
sb, 15C, 15d...Reflector, 21
a, 21 b, 22a, 22b --- Reflector. 3Q...Vacuum container. Name of agent: Patent attorney Toshio Nakao and 1 other person9-
Fig. 4 2h, 2fb - elbow shape ■ Fig. 5 2mu, 22b - J total Fig. 6
2

Claims (3)

[Claims] (1) In a microwave plasma generation device comprising a waveguide for transmitting microwaves, a vacuum container connected to the waveguide, and a discharge region formed in the vacuum container, the discharge is caused in the waveguide. At least two or more even number of reflecting plates that reflect microwaves are provided facing the area, and the reflecting plates are substantially parallel to each other, and the interval between them is 1/4 of the microwave wavelength in the tube. Microwave plasma generator. (2) The microwave plasma generation device according to claim 1, wherein the reflection plate is adjustable in angle. (3) The microwave plasma generation device according to claim 1, wherein the reflection plate is driven so that the angle formed with respect to the waveguide changes during plasma generation.