JPS632237A - Plasma generating device - Google Patents

Abstract

PURPOSE:To realize lightness and smallness of coils and besides the whole device, by installing a plasma generating chamber which is formed by narrowing down a rectangular waveguide at its end part in the electric field direction of microwaves so that the cross section is shaped into a slender rectangle, and then disposing magnetic field generators on both sides of the plasma generating chamber. CONSTITUTION:A waveguide 14 is formed so that its width in the electric-field direction (shown in an arrow E) of microwaves is equal to that of a rectangular guidewave 11. As the waveguide is extended from the part of the waveguide 15 to the part of a plasma generating chamber 16, it is narrowed down in steps so that the cross section of the plasma generating chamber 16 along the plane orthogonal to the advancing direction of the microwaves has a slender rectangular shape. Besides, an electromagnet 18 comprising a coil 18a and an iron core 18b, and another electromagnet 19 comprising a coil 19a and an iron core 19b, are disposed in symmetry to each other on both of the plasma generating chamber 16. Hence, the magnetic field can be applied effectively only to the plasma generating chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plasma generation device, and particularly to a microwave ion source using electron cyclotron resonance, that is, an ECR (Electron Cyclotron Resonance).
sonance) ion source.

[Traditional technique]

Figure 4 is an exploded perspective view of a conventional microwave ion source for an ion implanter. In the same figure, there is a ridge 1a on the inside.
What is the waveguide 1 and discharge box 2 that have the following?

They are connected across a dielectric window 3 for vacuum sealing.

The discharge box 2 has two discharge electrodes 4a and 4b provided near the center and spaced apart from each other, and these electrodes 4a and 4b.
It has dielectric windows 5a and 5b provided to sandwich it from above and below, and the central part surrounded by these serves as a plasma generation chamber. Furthermore.

A large coil 6 surrounds the discharge box 2.

A strong magnetic field is applied in the axial direction of the figure.

In the above device, microwaves generated by a microwave generation source (not shown) such as a magnetron are transmitted through the waveguide 1.
and is introduced into the discharge box 2 through the dielectric window 3. This microwave.

A strong microwave electric field is generated in a plasma generation chamber formed between discharge electrodes 4a and 4b. The magnetic field by the coil 6 is applied in a direction perpendicular to this electric field. To generate plasma in the plasma generation chamber, gas is introduced into the plasma generation chamber via a gas pipe (not shown). Then, in the plasma generation room.

High-density plasma is generated by the interaction of microwave electric and magnetic fields. Ions in this plasma can be extracted to the outside as an ion beam 9 by applying an appropriate voltage to the ion extraction electrode system 8.

[Problem that the invention seeks to solve]

In the conventional device described above, as is clear from FIG.

Because the coil 6 surrounds the entire structure, the magnetic resistance is very large, and in order to provide a strong magnetic field inside the plasma generation chamber, the cross section of the coil 6 must be made considerably large. As the size increases, there is a problem in that the entire device must also become larger.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional drawbacks, it is an object of the present invention to provide a plasma generating device that can reduce the weight and size of the coil, and further reduce the weight and size of the entire device.

[Means for solving problems]

In order to achieve the above object, the present invention provides a portion whose width is narrowed in the direction of the microwave electric field at the end of the rectangular waveguide and whose cross-sectional shape is an elongated rectangle, and this portion is used as a plasma generation chamber. A further feature is that magnetic field generators made of coils, permanent magnets, etc. are arranged on both sides of the plane of the plasma generation chamber orthogonal to the electric field direction, so that a magnetic field is applied from both sides.

[For production]

The microwave is guided to the plasma generation chamber by a rectangular waveguide. Since the plasma generation chamber is shaped like a rectangular waveguide whose width is narrowed in the direction of the electric field, the electric field of the microwaves guided therein becomes extremely strong.

Therefore, a strong plasma is generated by introducing gas into this plasma generation chamber, which has an elongated rectangular cross section, and applying an appropriate magnetic field from at least both sides.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to one drawing.

FIG. 1 is an exploded perspective view showing one embodiment of the present invention, and FIG. 2 is a cross-sectional view when assembled. In the figure, a rectangular waveguide 11 is connected to a waveguide 14 via a vacuum-sealing dielectric window 12 made of SiO2 or alumina, etc., and an O-ring 13 made of rubber. Furthermore, the waveguide 14
is connected to a plasma generation chamber 16 via a waveguide 15. Here, the waveguide 14 has the same length in the microwave electric field direction (arrow E) as the rectangular waveguide 11;
As it extends from the waveguide 15 to the plasma generation chamber 16, its length is narrowed in one step.

The cross-sectional shape of the plasma generation chamber 16 along a plane perpendicular to the direction of propagation of microwaves is an elongated rectangle. For example, rectangular waveguide 11.14 has an aspect ratio of 2:1, and waveguides 14, 15 . The width of the plasma generation chamber 16 is, for example, 55 mm and 23 mm.

It is narrowed down to lQu+. Furthermore, the length of the microwave in the direction of propagation is λ/4. The plasma generation chamber 16 is λ/2.

Further, on both sides of the plasma generation chamber 16, there are electromagnets 18 consisting of a coil 18a and an iron core 18b.

Electromagnets 19 made up of a coil 19a and an iron core 19b are arranged symmetrically to each other. Iron core 18b.

19b passes through the coils 18a and 19a, respectively, and is bent until both ends approach the plasma generation chamber 16, thereby making the magnetic resistance extremely small. With this positional configuration, it is possible to effectively apply a magnetic field (shown by a broken line in FIG. 2) whose axis is the same as the direction of microwave propagation and which has an ECR strength inside the plasma generation chamber 16.

In the above configuration, microwaves generated by a microwave generation source (not shown) such as a magnetron are propagated in the TEI mode by the rectangular waveguide 11.

The light passes through the dielectric window 12 and is guided into the waveguide 14 .

Here, the dielectric window 12 prevents unnecessary gas from entering the plasma generation chamber 16 from the rectangular waveguide 11 by separating the rectangular waveguide 11 and the plasma generation chamber 16. The microwave guided to the waveguide 14 is transferred to the waveguide 1
5, the microwaves reach the plasma generation chamber 16 through the waveguide 15 and the plasma generation chamber 1.
It is reflected at each entrance of 6. However, the length of the waveguide 15 is λ
/4, these reflected waves intersect with each other with a phase difference of 180 degrees. In other words, these reflected waves cancel each other out, thereby increasing the microwave transmittance. About this.

Since the length of the waveguide 14 is also set to λ/4, the same can be said about the reflection at each entrance of the dielectric window 12 and the waveguide 15. Furthermore, since the plasma generation chamber 16 has a narrow width in the microwave electric field direction (arrow E), the electric field of the microwave guided therein becomes extremely strong. In this state, when gas is introduced into the plasma generation chamber 16 via a gas pipe (not shown), a discharge occurs. Here, when the above-mentioned magnetic field is applied within the plasma generation chamber 16 by the electromagnets 18 and 19, an ECR discharge occurs due to the interaction between the above-mentioned electric field and this magnetic field, and a strong plasma is generated. Ions in this plasma can be extracted to the outside as an ion beam by applying an appropriate voltage to a two-ion beam extraction electrode system (not shown).

In this embodiment, the dielectric window 12 is provided at a position away from the magnetic field, so that the dielectric window 12 is not exposed to plasma and becomes contaminated.

In addition, in the above embodiment, two electromagnets 1 are used as the magnetic field generator.
8.19 are placed on both sides of the plasma generation chamber 16, but as shown in FIG.
0, and iron cores 21 and 22 may be arranged on both sides thereof. In this way, the magnetic resistance can be reduced by the iron cores 21 and 22, and the plasma generation chamber 1
6 can be effectively applied with a magnetic field.

〔Effect of the invention〕

As explained above, according to the present invention, a plasma generation chamber is created by narrowing the width in the electric field direction at the end of the microwave waveguide, and magnetic field generators are provided on both sides of this plasma generation chamber, so that the magnetic field can be used to generate plasma. It can only be given effectively to the room. Therefore, the magnetomotive force required for the magnetic field generator can also be very small, as there is no need for a coil to surround the entire device.

It is possible to reduce the weight and size of the coil and the like, and also to reduce the weight and size of the entire device.

Furthermore, since the magnetic field can be intensively applied to the plasma generation chamber, it is easy to provide a dielectric window outside the magnetic field. In this way, it is possible to prevent the dielectric window from being exposed to plasma and becoming dirty, and to extend its lifespan.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view showing one embodiment of the present invention. FIG. 2 is a cross-sectional view of the above embodiment. FIG. 3 is a cross-sectional view showing the main parts of another embodiment of the present invention. FIG. 4 is an exploded perspective view showing a conventional plasma generator. 11... Rectangular waveguide. 12...Dielectric window. 13...0-ring. 14.15... Waveguide. 16...Plasma generation chamber. 18.19...Electromagnet. 18a, 19a, 20...coil. 18b, 19b, 21.22... Iron core. Patent applicant Fujitsu Ltd. Same as above
Elionix Co., Ltd. Figure 3

Claims (3)

[Claims] (1) A rectangular waveguide for propagating microwaves, which is installed at the end of the rectangular waveguide, and generates plasma by absorbing the energy of the microwave propagated by the rectangular waveguide into a gas body. a magnetic field generator that applies a magnetic field having the same axis as the traveling direction of the microwave and having an ECR strength to the plasma generation chamber; and a magnetic field generator provided between the rectangular waveguide and the plasma generation chamber. and a dielectric window for vacuum-sealing the plasma generation chamber, the width of the rectangular waveguide being narrowed in the direction of the electric field of the microwave and perpendicular to the direction of propagation of the microwave. A portion having an elongated rectangular cross-sectional shape along the surface is provided, and the portion is used as the plasma generation chamber, and the magnetic field generator is placed outside at least one of the surfaces of the plasma generation chamber perpendicular to the electric field direction. A plasma generating device characterized by: (2) The plasma generating device according to claim 1, wherein the dielectric window is provided outside the magnetic field. (3) The plasma generating device according to claim 1, wherein the magnetic field generator is comprised of first and second magnetic field generating members that are separate from each other.