JPH02189841A - Microwave plasma generating device - 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] Industrial Application Field The present invention relates to a plasma generation device mainly used in microwave plasma devices used for surface modification, thin film formation, etching, etc. .

BACKGROUND OF THE INVENTION In recent years, various microwave plasma devices have been proposed that generate high-density plasma using a microwave power of 2.450) lz and a resonant magnetic field of 875 G.

FIG. 5 is an example described in Japanese Patent Application No. 11i3-20527, in which a coaxial tube 5 consisting of an inner conductor 3 and an outer conductor 4 is used as a means for transmitting microwave power 1 to a discharge chamber 2. .

This conventional example will be briefly explained below.

2 delivered from a microwave power oscillator (not shown)
, 45 GHz microwave power 1 is supplied into the discharge chamber 2 via a rectangular waveguide 6 and a coaxial tube 5.

At this time, the portion 3a of the inner conductor 3 located within the discharge chamber 2 acts as an antenna that radiates microwave power into the discharge chamber 2.

A microwave window 8 transmits the microwave power 1 and keeps the inside of the discharge chamber 2 in a vacuum, and is made of a dielectric material such as alumina or quartz. As shown in the figure, an inner conductor 3 passes through this microphone mouth wave window 8, and the two are joined together by brazing, glass frit, organic adhesive, etc. without leaking vacuum.

The microwave power radiated into the discharge chamber 2 is transmitted to the solenoid 9.
Electron cyclotron resonance plasma 10 is generated by the 875G resonance magnetic field generated by the electron cyclotron resonance plasma 10, which is used for thin film processing.

Note that 11 is a movable shorting plate for shorting the other end of the coaxial tube 5.

Furthermore, when the plasma 10 is generated, the part in contact with the plasma is heated to a high temperature, so cooling water 12 is flowed inside the inner conductor 3, and a cooling coil 13 in which cooling water is flowed is provided around the discharge chamber 2. It's cooling down.

Problems to be Solved by the Invention Although the above-mentioned conventional techniques can generate high-density plasma and improve the processing speed of thin films, higher speeds are desired from the viewpoint of productivity. As a method of satisfying this requirement, there is a means of increasing the microwave power supplied to the discharge chamber 2 to generate higher density plasma.

However, when a conventional microwave plasma device is operated for a long time with high-power microwaves applied, cracks 13 occur in the microwave window 8 in the circumferential and diametrical directions, as illustrated in FIG. Therefore, there was a problem that the vacuum inside the discharge chamber 2 could not be maintained.

The reason why such cracks 13 occur in the microwave window 8 is considered to be as follows.

That is, the inner conductor 3 is cooled by the cooling water 12 and is therefore at about room temperature, but the microwave window 8 cannot be cooled and is therefore heated to a high temperature by the plasma 1o. On the other hand, alumina or the like used for the microwave window 8 has extremely low thermal conductivity.

Therefore, as schematically illustrated in FIG. 7, the temperature distribution in the radial direction of the microwave window 8 is low at the portion in contact with the cooled inner conductor 3, and rapidly increases with the radius. Therefore, it is thought that distortion occurs in the microwave window 8 due to the difference in thermal expansion caused by this temperature difference, and cracks 13 as shown in FIG. 6 occur. In other words, the reason why the microwave window 8 cracks is because the cooled inner conductor 3 penetrates the microwave window 8 .

Means for Solving the Problems In order to solve the above problems, the present invention provides a microwave window made of a dielectric material that transmits microwave power and seals a vacuum.
The present invention is characterized in that a rod-shaped or plate-shaped conductor is disposed between the waveguide and the discharge chamber, and the conductor is disposed within the discharge chamber without touching the microwave window.

With the configuration described in "Operation" (2), microwave power can be supplied into the discharge chamber without passing through the inner conductor of the coaxial tube or the like to the microwave window. As a result, the temperature distribution of the microwave window becomes uniform,
It can solve the problem of cracks.

Embodiment A first embodiment of the present invention will be described with reference to FIG. In this embodiment, the same components as in the conventional example shown in FIG. 5 are designated by the same numbers.

In FIG. 1, reference numeral 14 denotes a circular waveguide having a microwave window 15 made of alumina that transmits the microwave power 1 and seals the vacuum, and is connected to the discharge chamber 2. A coaxial tube 16 transmits the microwave power 1 to the circular waveguide 14, and is composed of an inner conductor 17 and an outer conductor 18. The length can be adjusted in the direction of arrow a in order to adjust the amount. The length of the inner conductor 17 can be adjusted from the position where the tip of the inner conductor 17 is in contact with the microwave window 15 to the position shown in the figure.

With this configuration, the microwave power 1 is transmitted from the coaxial tube 16 to the circular waveguide 14, transmitted through the microwave window 15, and supplied to the discharge chamber 2.

In addition, a rod-shaped conductor 19 is placed inside the microwave window 1 in the discharge chamber 2.
It is placed without touching 5. This conductor 19 is the fifth
Like the conventional antenna 3a shown in the figure, it functions as an antenna that radiates microwaves into the discharge chamber 2, and plasma 10 is generated by the radiated microwaves. Note that the conductor 19
In this embodiment, two ceramic rods 20 are fixed to the discharge chamber 2.

In this embodiment, the inner conductor 17 of the coaxial tube 16 does not pass through the microwave window 15 as in the conventional example. Therefore, the microwave window 15 is heated by the plasma 10, but as shown in FIG. 6 of the conventional example, the microwave window 8 is cooled by the cooling water 12 flowing through the inner conductor 3, causing a rapid temperature distribution in the microwave window 8. It never occurs. That is, microwave window 1
Since the temperature of the microwave window 5 is almost uniform, distortion due to thermal expansion is slight, and the problem of cracking of the microwave window 15 does not occur.

Next, a second embodiment of the present invention is shown in FIG.

This embodiment is an example in which the coaxial tube 16 of the first embodiment is removed and a microwave window 15 is provided at the end of the circular waveguide 14.

Furthermore, a third embodiment of the present invention is shown in FIGS. 3 and 4. This embodiment is an example in which the conductor 19 of the first embodiment is shaped like 21 in order to radiate microwaves more uniformly into the discharge chamber 2.

In the second embodiment, the conductor 19 is placed inside the discharge chamber 2.
Although 21 has a rod shape, the present invention is not limited to a rod shape, and may be a plate shape or the like. Also, the microwave window 15
The waveguide having this is not limited to a circular waveguide, but may be a rectangular waveguide or the like.

In addition, in each of the embodiments mentioned above, the case where the present invention was used as a plasma source was explained, but the present invention is not only used as a plasma source, but also can be used as an ion source by providing an electrode for extracting ions, etc. It can also be applied in cases.

Furthermore, the frequency of the microwave and the strength of the magnetic field are each 2.
The present invention is not limited to 45 GHz and 875 G, nor is the generated plasma limited to electron cyclotron resonance plasma.

Effects of the Invention According to the present invention, since the problem of cracking of the microwave window does not occur, it is possible to obtain a plasma generation device that can input high-power microwaves and improve the processing speed of thin films.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a microwave plasma generator according to a first embodiment of the present invention, FIG. 2 is a longitudinal cross-sectional view of a microwave plasma generator according to a second embodiment of the present invention, and FIG. A vertical cross-sectional view of a microwave plasma generator according to a third embodiment of the present invention, FIG. 4 is a cross-sectional view thereof, FIG. 5 is a vertical cross-sectional view of a conventional example, and FIG. FIG. 7 is an explanatory diagram of the temperature distribution that occurs in a conventional microwave window. 2. Bottle Φ discharge chamber, 14 --- waveguide, 15... microwave window, 19.21... fist conductor. Name of agent: Patent attorney Shigetaka Awano (1 person) Figure 7 Figure 1?

Claims (3)

[Claims] (1) A microwave window made of a dielectric material that transmits microwave power and seals the vacuum is placed between the waveguide and the discharge chamber, a rod-shaped or plate-shaped conductor is placed inside the discharge chamber, and the conductor A microwave plasma generator characterized in that the microwave plasma generator is arranged without contacting the microwave window. (2) The microwave plasma generator according to claim 1, wherein the microwave transmission circuit that supplies microwave power to the waveguide is a coaxial tube. (3) The microwave plasma generator according to claim 2, wherein the length of the inner conductor of the coaxial tube that supplies microwave power to the waveguide is adjustable.