JPS6273530A - ion source - 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 [Field of Application of the Invention] The present invention provides an ion source, in particular, a permanent magnet is disposed on the outer wall of a plasma chamber into which a gas or the like is introduced and the gas is turned into plasma. This invention relates to a type of ion source in which the ion source is confined by a caps magnetic field.

[Background of the invention]

This type of ion source is disclosed in, for example, Japanese Patent Application Laid-Open No. 57-78800.
The one described in the publication number is known. Moreover, in conventional ion sources, arc discharge occurs between the filament and the inner wall of the plasma chamber, but the heat generated by this arc discharge is generated by the permanent magnet placed on the outer wall of the plasma chamber. A phenomenon occurs in which the permanent magnet is heated. When a permanent magnet is heated above a certain level (TL (150G)), a so-called demagnetization phenomenon occurs, which also has the disadvantage of not being able to return to its original magnetic field.

Therefore, normally, a water-cooled tube is placed in the ion source near the permanent magnet to prevent the permanent magnet from reaching a temperature above a certain value.

However, even if the water-cooled tubes were arranged, the degree of freedom in their arrangement was hindered by the permanent magnets or their current introduction terminals. As a result, there are areas where it is difficult to arrange the water-cooled tubes, cooling of the permanent magnets in these areas cannot be achieved, and no consideration has been given to reliable prevention of the demagnetization phenomenon of the permanent magnets.

[Purpose of the invention]

The object of the present invention has been made based on the above circumstances, and is to provide a nine ion source that can reliably prevent the demagnetization phenomenon of a permanent magnet due to heat.

[Summary of the invention]

In order to achieve this objective, the present invention provides a plasma chamber in which a permanent magnet is disposed on the outer wall of a plasma chamber into which gas or the like is introduced and the gas is turned into plasma, and the permanent magnet is used to confine the plasma by a Kags magnetic field. In the ion source, an inner chamber with good thermal conductivity is arranged along the inner surface of the plasma chamber, and a heat escape means is provided between the inner chamber and the plasma chamber.

[Embodiments of the invention]

FIG. 1 is a sectional view showing an embodiment of an ion source according to the present invention. First, there is a plasma chamber 1.
A pair of current introduction terminals 3 are fixedly installed on the upper part of the plasma chamber 1, and a filament 2 is disposed extending from the current introduction terminals 3 into the plasma chamber 1, respectively. Further, a gas introduction port 4 is arranged approximately at the center of each of the current introduction terminals 3, and a predetermined gas can be introduced into the plasma chamber 1 through this gas introduction port 4. In addition, permanent magnets 6 for forming a caps magnetic field in the plasma chamber 1 are arranged on the upper outer side and the outer wall of the nine-plasma case 1, which is equipped with such a current introduction terminal 3 and a gas introduction port 4. ing. The permanent magnets 6 disposed in the upper part of the plasma chamber 1 are arranged concentrically around the gas inlet 4t and have a polycyclic shape. Further, on the outer wall of the plasma chamber 1, rod-shaped magnets are arranged in parallel along the circumference of the outer wall along the central axis of the plasma chamber 1, and are arranged radially as a whole as shown in the plan view of FIG. It has become something like this. Further, an electrode 7 is arranged at the bottom of the plasma chamber 1.

Further, an inner chamber 5 is disposed on the inner wall of the plasma chamber 1, having a slight gap with the inner wall surface, extending along the circumferential direction of the inner wall, and having an overall cylindrical shape. . This chamber is made of, for example, stainless steel or molybdenum. This inner chamber 5
The upper end portion and the lower end portion are each formed to have a slightly thicker wall thickness, so that they are in contact with the inner wall of the plasma chamber 1, and at this contact portion, the plasma chamber 1
and is fixed by bolt 8.

Further, a disk-shaped inner chamber 5 is disposed on the upper inner wall of the plasma chamber 1 with a slight gap between the upper inner wall surface and the upper inner wall surface. The peripheral part of this inner chamber 5 is formed to have a slightly thicker wall thickness, so that it comes into contact with the upper inner wall of the plasma chamber 1, and at this contact part,
It is fixed to the plasma chamber 1 with bolts 8.

The ion source configured in this manner causes arc discharge to occur during this period by passing a current through the inner chamber 5 as an anode and the filament 2 as a cathode. This arc discharge ionizes the gas within the plasma chamber 1 to generate plasma. This plasma is placed outside the plasma chamber 1 and is confined within the plasma chamber 1 by a Cassis magnetic field produced by nine permanent magnets 6.

At this time, the inner chamber 5 is heated by the arc discharge, but since there is a gap between the inner chamber 5 and the inner wall surface of the plasma chamber 1, the bolts 8 fixed to the upper and lower ends of the plasma chamber 1 are inserted. Heat will be dissipated through.

Therefore, heat is not directly conducted to the wall surface of the plasma chamber 1 where the permanent magnets 6 are arranged. Therefore, the heating of the permanent magnet 6 of 1000 or more can be completely suppressed, and the demagnetization phenomenon of the permanent magnet 6 can be reliably prevented.

In the embodiment described above, the inner chamber 5 is arranged with a slight gap formed between it and the inner wall of the plasma chamber 1. However, as shown in FIG.

The inner channel (5) may be brought into contact with the inner wall of the plasma chamber 1 without forming the gap.

Even in this case, the contact portion is connected to the inner chamber 5.
Since a minute gap layer is formed due to the surface roughness of the inner wall of the plasma chamber 1, a sufficient effect can be achieved in terms of thermal conductivity. FIG. 3 shows a cross-sectional view taken along the line AA in FIG. 2, and shows that the inner chamber 5 and the inner wall of the plasma chamber 1 are in contact with each other.

〔Effect of the invention〕

As is clear from the above explanation, according to the ion source according to the present invention, it becomes possible to reliably prevent the demagnetization phenomenon due to heat of the permanent magnet.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the ion source according to the present invention, FIG. 2 is a cross-sectional view showing another embodiment of the ion source according to the present invention, and FIG. FIG. 1... plasma chamber, 2... filament, 5...
Inner chamber, 6... permanent magnet.

Claims (1)

[Claims] 1. In an ion source in which a permanent magnet is arranged on the outer wall of a plasma chamber where gas, etc. is introduced and the gas is turned into plasma, and the permanent magnet confines the plasma by a cupped magnetic field, a permanent magnet is placed on the inner surface of the plasma chamber. An ion source characterized in that an inner chamber with good thermal conductivity is arranged along the plasma chamber, and a heat escape means is provided between the inner chamber and the plasma chamber.