JPS63228549A - Microwave polyvalent ion source - Google Patents

Abstract

PURPOSE:To make a large current polyvalent ion beam securable by setting up the drawer slit direction installed on a drawer electrode in accord with a plasma confinement area form to be formed by a composite magnetic field between the magnetic field generated in the ion drawing direction and that generated in and around the outer wall of a plasma chamber. CONSTITUTION:A magnetic field impressed on a plasma chamber 3 is generated by a solenoid coil 1 and a permanent magnet 6. A microwave is led into the plasma chamber 3 through an insulator 4, and the plasma generated in the plasma chamber 3 is drawn out of a drawer electrode system 5, and an ion beam 2 is thus secured. On the other hand, if the direction of a drawer electrode slit 8 is determined in accord with a plasma confinement area sectional form where a composite magnetic field between the axial magnetic field made by the solenoid coil 1 and the magnetic field generated in and around the outer wall of the plasma chamber 3, an ion moves along a line of magnetic force of the composite magnetic field, so that the polyvalent ion generated in plasma heads for the drawer electrode slit 8 so efficiently. A large current polyvalent ion can be therefore made securable.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a microwave ion source that can ionize a sample gas into multivalent ions and efficiently obtain an ion beam. The present invention relates to a microwave multi-charged ion source suitable for extracting a multi-charged ion beam.

[Conventional technology]

Regarding the plasma chamber structure of a microwave ion source, Japanese Patent Publications No. 57-4056, No. 11093, No. 11094,
There are coaxial structure and ridge structure as described in Japanese Patent Publication No. 59-8959, etc., and cylindrical structure as described in Japanese Patent Publication No. 53-34461.

On the other hand, although it is slightly different from the microwave ion source mentioned above,
Clear Instruments and Methods in
Physics Research B10/11 (1985) pp. 775-778 (Nucl, Engn5tr, an
d Meth, jn Phys, Res.

B10/11 (1985) PP775-778), in addition to the magnetic field in the ion beam extraction direction by the solenoid coil, by providing an octupole magnetic field on the outer wall of the plasma chamber, the extraction current for multiply charged ions can be significantly increased. I know it will improve. This is called an ECR ion source.

Like the microwave ion source described above, this is an ion source that extracts an ion beam from plasma generated by microwave discharge in a magnetic field.

[Problem that the invention seeks to solve]

Based on the above background, ideas have been made to arrange magnets or the like on the outer peripheral wall of the plasma chamber in microwave ion sources as well, in order to increase the efficiency of multiply charged ion production. However, in an ECR ion source or a microwave ion source with a multipolar magnetic field,
Ion extraction i for large current beam extraction! ! Optimization of pole placement was not devised.

An object of the present invention is to obtain a high-current multiply charged ion beam by providing an ion source with an extraction electrode arrangement suitable for a microwave ion source with a multipolar magnetic field.

[Means for solving problems]

Efficient generation of multiply charged ions in a sample gas using a microwave ion source is achieved by placing something that generates a magnetic field, such as a permanent magnet or an electromagnet, near the outer wall of the plasma chamber.

On the other hand, in order to extract a multicharged ion beam as a large current from the generated plasma, it is necessary to provide an optimal method for attaching electrodes according to the configuration in which a multipolar magnetic field is added. The purpose of this is to arrange the direction of the extraction slit on the extraction electrode in accordance with the shape of the plasma confinement region formed by the combined magnetic field of the magnetic field generated in the ion beam extraction direction and the magnetic field generated near the outer wall of the plasma chamber. This is achieved by

[Effect]

In addition to the solenoid coil that applies a magnetic field in the direction in which the ion beam is extracted, if a device that generates another magnetic field is placed near the outer wall of the plasma chamber, the plasma generated by the microwave discharge can be effectively confined. As the confinement efficiency increases, the lifetime of ions becomes longer, and the number of collisions between these ions and high-speed electrons generated by microwave discharge increases, making it possible to efficiently generate multivalent ions.

On the other hand, if the direction of the extraction electrode slit is determined according to the cross-sectional shape of the plasma confinement region formed by the composite magnetic field of the axial magnetic field by the Lunoid coil and the magnetic field generated near the outer wall of the plasma chamber, ions will follow the lines of magnetic force of the composite magnetic field. Because of this movement, the multivalent ions generated in the plasma efficiently move toward the extraction electrode slit. Therefore, it becomes possible to efficiently obtain a large current multiply charged ion beam.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. The magnetic field applied to the plasma chamber 3 is generated by the solenoid coil 1 and the permanent magnet 6. Microwaves are introduced into the plasma chamber 3 through the insulator 4. plasma chamber 3
The plasma generated is extracted from an extraction electrode system 5 to obtain an ion beam 2. An experiment was conducted using the arrangement of peripheral magnets shown in FIG. 2, and it was experimentally found that the plasma confinement shape in which many plasma particles exist is the shape shown by 7. For this reason, the direction of the extraction electrode slit 8 was arranged in the direction of the opposing south pole magnet in this embodiment. Note that when the arrangement is the same and only the direction of the current flowing through the solenoid coil is changed, the shape shown by diagonal lines in FIG. 2 becomes a plasma confinement shape that is inclined by 45 degrees, and becomes a plasma confinement shape that becomes elongated in the north pole direction. In this case, the direction of the slit 8 was arranged to match the direction of the opposing north pole.

Furthermore, for the plasma confinement shape 7 shown in FIG.
When the ion beam current extracted by rotating the slit 8 was measured, the maximum value was obtained with the arrangement shown in FIG. 2.

In addition, the plasma chamber inner diameter in the embodiment shown in FIG. 1 is approximately 92 mm in diameter.
mm, and the length is 200 mm. Furthermore, a 2.45 GHz microwave was used. The magnetic field strength generated by the solenoid coil is 0.5 to 1.5 kilogauss, and the permanent magnet is made of samarium cobalt.
Its surface magnetic flux density is 9 kilogauss. When an extraction voltage of 3 kV was applied to the electrode in the arrangement shown in Figure 2, a voltage of 2 mm
Unprecedented 1 mA for a slit size of ×40 mm
A high extraction current density of /cm2 or more was obtained. According to the present invention, it is possible to efficiently extract a large current beam from a microwave multiply charged ion source. [Effects of the Invention] According to the present invention, multiply charged ions of a sample gas can be generated by microwave discharge. Since it is possible to efficiently extract the generated multivalent ions as an ion beam, there is a significant effect in improving the performance of an ion source for a high-energy ion implantation device when put into practical use.

By implanting ions with high energy, material modification deep into the surface and three-dimensional surface modification are possible. On the other hand, the fact that the necessary ions 1 can be implanted into the material in a short time means that
This means that productivity will improve, which will also lead to lower costs.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a basic embodiment of the present invention, and FIG.
The figure is a conceptual cross-sectional view of FIG. 1. 1...Solenoid coil, 2...Ion beam, 3
... plasma chamber, 4... insulator, 5... extraction electrode system, 6... permanent magnet, 7... plasma region, 8...
・Extractor electrode slit

Claims (1)

[Claims] 1. A plasma chamber that supplies microwaves to generate plasma of sample gas, a solenoid coil that generates a magnetic field in the plasma chamber, a plurality of permanent magnets or electromagnets installed near the outer wall of the plasma chamber, and a plasma chamber. In a microwave ion source consisting of an extraction electrode system for extracting an ion beam from a plasma confinement region, the plasma confinement region is formed by a composite magnetic field of a magnetic field created by the solenoid coil and a magnetic field created by the permanent magnet or electromagnet. A microwave multivalent ion source characterized in that the direction of the extraction electrode slit is aligned with the direction of the slit of the extraction electrode. 2. Two or more permanent magnets or electromagnets placed near the outer wall of the plasma chamber are arranged in a line along the ion beam extraction direction, and the polarity of each group is the same, and such a group is The microwave multivalent ion source according to claim 1, wherein the microwave multivalent ion source is arranged along the circumferential direction of an outdoor wall. 3. The microwave multiply charged ion source according to claim 1, wherein the permanent magnets or electromagnets provided in the circumferential direction of the outer wall of the plasma chamber are arranged so that the polarity of the magnetic field is alternated.