JPH01241798A - Microwave plasma device - Google Patents

Abstract

PURPOSE:To easily control a state of discharge with simple constitution by arranging a conductor an inner conductor and an outer conductor of a discharge chamber. CONSTITUTION:A conductor 19 is arranged between an inner conductor 6 and an outer conductor 7 of a discharge chamber 8. The conductor 19 is rod-shaped while having the same shape with a Langmuir probe and being able to generate high density discharge in a low magnetic field by using the conductor 19. Further, the discharge state can be adjusted and controlled by changing its insertion length automatically or manually. Accordingly, discharge in a weak magnetic field becomes able and a solenoid can be made small-sized, further, power supply for the solenoid can be of small capacity so as to have small power consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a microwave plasma apparatus for thin film processing used in film formation, etching, ion implantation, and the like.

BACKGROUND OF THE INVENTION In recent years, plasma apparatuses using microwave discharge have been developed in order to improve the processability and processing speed of thin films. An example of this is a microwave ion source using a coaxial tube type discharge chamber (for example, "Rev.

Nissii, NTSrlmj
(Rev, Sci, xnstrum, , 57(8
), Pl 526 (1986)) is shown in FIG.

In Fig. 6, reference numeral 1 denotes a 2.45 GHz micropower oscillator, and the microwave generated by this is transmitted through a rectangular waveguide 2, and a coaxial tube 6 consisting of an inner conductor 3 and an outer conductor 4.
The inner conductor 6 and outer conductor 7 connected to this coaxial pipe 6
A plasma 9 is generated by being supplied into a discharge chamber 8 consisting of.

A ceramic window 1o with low dielectric loss for vacuum sealing is provided between the coaxial tube 5 and the discharge chamber 8.
and the vacuum chamber 11 are electrode systems 12-IL, 12-b, for extracting ions from the plasma 9.
12-0. 13, 14, 15, and 16 are parts of the microwave transmission circuit, which are an isolator, a power monitor, a choke flange, and a movable shorting plate, respectively.

Further, 17-&, 17-b, and 17-c are solenoids for generating electric discharge. This solenoid 17
-IL~17-C, on the central axis of the discharge tube 8, the maximum part is about 2000 Gauss and the lowest part is about 10 Gauss.

A mirror magnetic field of Gaussian magnitude is created to increase the absorption of microwaves into the plasma, thereby increasing the density of the plasma.

This microwave ion source can extract ions with a large current and uses a coaxial tube type discharge chamber.
It has the excellent feature that the diameter can be designed to any size.

Problems to be Solved by the Invention However, the conventional configuration described above requires a strong magnetic field of about 2000 Gauss, making the solenoid large in size, and also requiring a large capacity power supply for the solenoid. There was a problem that power consumption increased.

Furthermore, in the conventional plasma apparatus described above, it is relatively difficult to control the discharge state to a constant level, and a simple control method has been desired.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a microwave plasma device that has a simple configuration and can easily control the discharge state.

Means for Solving the Problems In order to solve the above problems, in the present invention, a rod-shaped or plate-shaped conductor is arranged between the inner conductor and the outer conductor of the coaxial tube type discharge chamber, parallel to or perpendicular to the outer conductor of the discharge chamber. do.

Operation The present invention allows discharge in a very low magnetic field due to the above-mentioned configuration, and furthermore, the discharge state can be changed by changing the length of the arranged conductor.

EXAMPLE Before explaining the present invention in detail, first, the background to the invention will be explained.

The present inventors have developed an ion source having a large-diameter coaxial tube type discharge chamber using a prototype machine shown in FIG.

, @Figure 6 omits the parts of the microwave oscillator and microwave transmission circuit, and only shows the discharge chamber rotation, but these parts are connected as in the conventional example shown in Figure 6. . In FIG. 6, the same components as in FIG. 6 are given the same numbers.

The rectangular waveguide 2 for the 2,45 GHz band shown in the conventional example in FIG. 6 has a cross-sectional dimension of 109.2 ff.
1m x 64.6III) Coaxial pipe 6 is 109.
Since it is necessary to connect to a surface of 2 mm, the inner diameter of the coaxial tube 5 must be 109,2 (1 m or less) in diameter.

Therefore, the inner diameter of the outer conductor of the discharge chamber 8 is set to 109.2 m in diameter.
In order to make the diameter larger than m, the impedance of each of the coaxial tube 6 and the discharge chamber 8 must be matched, and a part of the taper with a length of about an integral multiple of 1/4 wavelength must be provided between the inner conductor and the outer conductor. It is necessary to gradually change the diameter of the conductor.

However, from the standpoint of miniaturizing the device, it is not preferable to provide a tapered part, and the inventors have proposed that the coaxial space be 5 as shown in FIG.
and the discharge chamber 8 are directly connected.

In FIG. 6, 1B is a Langmuir probe for measuring plasma characteristics, and it is constructed by covering a tungsten wire with a thickness of 0.21 with glass, and as shown in the figure, it is placed parallel to the outer conductor of the discharge chamber 8. The tip is bent at right angles to the outer conductor 7 and directed toward the center.

In this ion source, when the Langmuir probe 18 is inserted, plasma is generated when the central magnetic field of the solenoid 17 is about 700 to 1000 Gauss, and this plasma absorbs microwaves with almost no reflection and emits ions with a large current. When you take it out, it will form a hole.

However, if the Langmuir probe 18 is removed, no plasma is generated. Moreover, even if the Langmuir probe 18 is attached, the strength of the discharge will vary depending on the insertion depth.

The cause of this is currently unknown, but if this phenomenon is used, high-density plasma can be generated without the need for a strong magnetic field of 2,000 Gauss as in the conventional example, and ions can be generated with a large current. I can put it out.

The present invention has been made in view of the above phenomenon, and by arranging a conductor such as the Langmuir probe 18 between the inner conductor 6 and outer conductor 7 of the discharge chamber 8, it is possible to achieve high density in a low magnetic field. The aim is to enable a wide range of discharge, and to adjust the state of the discharge by changing the length of the conductor.

A first embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows only the main parts of the present invention, e) is a sectional view, and ('b) is a bottom view seen from the bottom. 6 and the same components as in FIG. 6 are given the same numbers.

In FIG. 1, 19 is the inner conductor 6 and outer conductor 7 of the discharge chamber 8.
A conductor placed between the In this embodiment, the conductor 19 is a bar with a shape similar to that of the above-mentioned Langmuir probe, and by using the conductor 19, a high-density discharge can be generated in a low magnetic field, and furthermore, the insertion length can be adjusted automatically or The discharge condition can be adjusted and controlled by changing it manually.

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

Similar to FIG. 1, (&) and ('b) in FIG. 2 are a sectional view and a spinal view, respectively, and the same components as in FIG. 1 are given the same numbers.

In FIG. 2, 191L is a conductor placed between the inner conductor 6 and outer conductor 7 of the discharge chamber 8.

The conductor 191L is inserted parallel to the outer conductor 7 like the Langmuir probe 18 in FIG. It is placed.

By using this conductor 19a, a high-density discharge can be generated in a low magnetic field, and further, by changing the insertion length by an automatic mechanism (not shown) or manually, the discharge state can be adjusted and controlled.

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

Similar to FIG. 1, FIGS. 3(a) and 3(b) are a sectional view and a bottom view, respectively, and the same components as in FIG. 1 are given the same numbers.

In FIG. 3, 19b is a conductor placed between the inner conductor 6 and outer conductor 7 of the discharge chamber 8. The conductor 19b is inserted at right angles to the outer conductor 7 like the tip of the Langmuir probe 18 in FIG. 6, and in this embodiment, a plurality of conductors are arranged.

By using this conductor 1sb, a high-density discharge can be generated in a low magnetic field, and further, by changing its insertion length, the discharge state can be adjusted and controlled.

Further, a fourth embodiment of the present invention is shown in FIG.

Similar to FIG. 1, FIGS. 4(&) and (b) are a sectional view and a bottom view, respectively, and the same components as in FIG. 1 are given the same numbers.

In FIG. 4, ff90 is a conductor placed between the inner conductor 6 and outer conductor 7 of the discharge chamber 8.

The conductor 19Q is the same as the conductor 19 shown in FIG.
' are arranged symmetrically.

By using this conductor 190, high-density discharge can be generated in a low magnetic field, and further, by changing the insertion length, the discharge state can be adjusted and controlled.

In this embodiment, a rod-shaped conductor is used as the conductor disposed between the inner conductor and the outer conductor of the discharge chamber, but the conductor is not limited to a rod shape, and may be a plate-shaped conductor.

Effects of the Invention By using the present invention, it is possible to discharge in a weak magnetic field, the solenoid can be made smaller, and the power supply for the solenoid can also be of small capacity, resulting in less power consumption. Can be done.

Furthermore, according to the present invention, it is possible to obtain the effect that the state of discharge can be easily controlled.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a microwave plasma apparatus according to a first embodiment of the present invention, FIG. 2 is a schematic diagram of a second embodiment of the present invention,
FIG. 3 is a schematic diagram of a third embodiment of the present invention, FIG. 4 is a schematic diagram of a fourth embodiment of the present invention, and FIG. 6 is a configuration diagram of a conventional example.
FIG. 6 is a schematic diagram of the discharge chamber. 3... Inner conductor of coaxial tube, 4... Outer conductor of coaxial tube, 6... Coaxial tube, 6... Inner conductor of discharge chamber, T ...Outer conductor of the discharge chamber, 8...
...Discharge chamber, 19,191L. 19b, 190... Conductor. (b) Figure 2 (α2 (wa) Figure 4 (and 2. (b) Figure 5 Figure 6

Claims (3)

[Claims] (1) Consists of a coaxial tube configured with an inner conductor and an outer conductor for transmitting microwave power, and a coaxial tube-type discharge chamber configured with an inner conductor and an outer conductor connected to the coaxial tube. A microwave plasma device with a conductor placed between the inner and outer conductors. (2) The microwave plasma device according to claim 1, wherein the conductor disposed between the inner conductor and the outer conductor of the discharge chamber has a rod-like or plate-like shape located parallel to or at right angles to the outer conductor of the discharge chamber. (3) The microwave plasma device according to claim 1, wherein the discharge state is controlled by changing the length of a conductor placed between the inner conductor and the outer conductor of the discharge chamber.