JPH0578897B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion source having a structure in which a vacuum container and a lining plate are provided inside the lid thereof.

[Conventional technology]

A conventional example of this type of ion source is shown in FIG.

That is, this ion source includes a cylindrical vacuum container 2, and an ion beam 2 is placed near one opening of the container.
Two lead-out electrodes 6 are provided, and the other opening side is covered with a lid 10. 8 is an O-ring for vacuum sealing. Further, a magnet 4 for generating a plasma confinement magnetic field is provided on the outside of the vacuum container 2, and a filament 14 is attached to the inside of the lid 10 via a bushing 12.

There is a first tube inside the vacuum container 2 that covers it.
A second lining plate 16 (also called a heat shield plate; the same applies hereinafter) is provided on the inside of the lid 10, and a second lining plate 18 is provided inside the lid 10 to cover it. 2,
Although it is thermally insulated from the lid 10, it is electrically at the same potential as them. Then, the plasma generation chamber 2 is connected by the electrode 6 and the lining plates 16 and 18.
It constitutes 0.

Note that the electrode 6 also serves as a heat shield plate, and it is preferable to use a nonmagnetic high-melting point metal for the electrode 6 and the lining plates 16 and 18.

The inside of the plasma generation chamber 20 is evacuated and a vapor or gaseous ion source material is introduced therein from an inlet (not shown), the filament 6 is turned on to bring it to a card potential, and the lining plate 16 is brought to an anode potential. When an arc discharge is caused between the ion source materials, the ion source material is turned into plasma and a plasma is generated in the plasma generation chamber 20, from which an ion beam 22 is extracted by the action of an electric field by the electrode 6.

In that case, by providing the lining plates 16 and 18, the ion source material with a low saturated vapor pressure is introduced into the plasma generation chamber 20 because they are heated to a high temperature by the radiant heat from the filament 14 and the heat due to arc discharge. Even if they do, they are less likely to adhere to the lining plates 16 and 18, making it easier to maintain the gas density within the plasma generation chamber 20 and, therefore, to maintain arc discharge.

[Problem to be solved by the invention]

However, in the above-mentioned ion source, the temperature of the inner lining plates 16 and 18 is fixed at a certain temperature if the heating power applied to them from the filament 14 etc. is constant because their surface areas are constant. Therefore, it is not possible to deal with ion source substances having lower saturated vapor pressures, that is, there is a problem that the ion source substances tend to adhere to the lining plates 16 and 18, making it difficult to maintain the gas density in the plasma generation chamber 20. .

Therefore, this invention improves these points and
The main object of the present invention is to provide an ion source that can be used with ion source materials having various saturated vapor pressures.

[Means to solve the problem]

In order to achieve the above object, the ion source of the present invention is sized such that the lid and the second lining plate can be placed inside the first lining plate, and the lid is cooperating with the ion source of the ion source. The lid is attached to an inner cylinder that closes the other opening side of the vacuum container and is large enough to be placed inside the first lining plate, and the inner cylinder is replaceable or movable. Also, the surface area of the portion of the first lining plate constituting the plasma generation chamber is made variable by making the position of the second lining plate variable.

[Effect]

According to the above configuration, by replacing or moving the inner cylinder, the surface area of the portion of the first lining plate that constitutes the plasma generation chamber can be changed, so that the surface area of the portion of the first lining plate that constitutes the plasma generation chamber can be changed. The total surface area of the lining board is variable. As a result, the heating power per unit area entering the first and second lining plates becomes variable, and their temperature can be set to an optimal temperature depending on the saturated vapor pressure of various ion source materials, Therefore, it becomes possible to deal with various ion source materials.

〔Example〕

FIG. 1 is a sectional view showing an ion source according to an embodiment of the present invention. The same reference numerals are given to the same or corresponding parts as in the example of FIG. 3, and the differences from the conventional example will be mainly explained below.

In this embodiment, a lid 10 as described above is used.
and the second lining board 18, the first lining board 1
The size (external dimensions) is such that it can be placed inside the 6.

In addition, an inner cylinder 26 of a size that can be placed inside the lining plate 16 is prepared, and its flange on one end is vacuum-sealed to the end of the vacuum container 2 as described above with an O-ring 8. At the same time, attach the lid 1 to the flange on the other end.
0 is attached in a vacuum-sealed state with an O-ring 24, and the other opening side of the vacuum container 2 is closed by the cooperation of this inner cylinder 26 and the lid 10, and furthermore, this inner cylinder 26 are made interchangeable.

Therefore, according to this structure, by replacing the inner cylinder 26 and changing its length, the positions of the lid 10, the lining plate 18, etc. within the lining plate 16 can be changed, and thereby the lining plate 16 The surface area of the parts constituting the plasma generation chamber 20 can be changed.

As a result, for example, assuming that the heating power to the lining plates 16 and 18 due to radiant heat from the filament 14 or heat from arc discharge is constant, the plasma generation chamber 20 of the lining plate 16 can be opened by inserting the lid 10, the lining plate 18, etc. inside. The smaller the surface area of the constituent parts, the smaller the lining plate 16 constituting the plasma generation chamber 20.
The total surface area of lining plates 16 and 18 also becomes smaller, and as a result, the heating power per unit area entering them becomes larger, and the inner lining plates 16 and 18 are heated to a higher temperature, so that they can also accommodate ion source materials with lower saturated vapor pressures. You will be able to do this. That is, it becomes possible to reduce the adhesion of the ion source material to the lining plates 16 and 18 and increase the gas density within the plasma generation chamber 20.

In that case, the ion generation efficiency in the plasma generation chamber 20 is generally better when the volume of the plasma generation chamber 20 is large and the gas density therein is high. Although there is a contradictory relationship between reducing the surface area of the plates 16 and 18 and increasing their temperature to increase the gas density and increasing the volume of the plasma generation chamber 20, it is possible to appropriately select the length of the inner cylinder 26. For example, it is possible to select conditions that are compatible with both conditions, thereby making it possible to optimize the ion production efficiency for ion source materials with various saturated vapor pressures.

In other words, according to the above structure, it is possible to deal with ion source materials of various saturated vapor pressures without changing the vacuum container 2 or the magnet 4, and it is possible to minimize the ion generation efficiency. You will also be able to do

FIG. 2 is a sectional view showing an ion source according to another embodiment of the invention. To explain the difference from the embodiment shown in FIG. 1, in this embodiment, the inner cylinder 26 is movable. That is, the inner cylinder 26 is supported by the vacuum container 2 so as to be movable back and forth using an adjustment bolt 32, a guide rod 36, etc., and is attached to the end of the vacuum container 2 in a vacuum-sealed state with an O-ring 8. A bellows 30 is provided between the flange 28 and the flange portion of the inner cylinder 26, thereby providing a vacuum seal between the inner cylinder 26 and the vacuum container 2.

The adjustment bolt 32 is screwed into a female threaded portion 34 provided on the outside of the vacuum container 2.
By rotating the inner cylinder 26, the inner cylinder 26 can be moved as shown by the arrow, and the positions of the lid 10, the lining plate 18, etc. attached thereto can be changed within the lining plate 16.

Therefore, if we compare the previous example and this example,
The former has a simple mechanism and is low cost, whereas the latter does not require replacing the inner cylinder 26, so it is labor-intensive and does not require breaking the vacuum in the plasma generation chamber 20. There is a characteristic that.

〔Effect of the invention〕

As described above, according to the present invention, the temperature of the first and second lining plates can be set to the optimum temperature according to the saturated vapor pressure of various ion source materials, and as a result, various ion source materials can be used. It becomes possible to correspond to the ion source material.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an ion source according to an embodiment of the present invention. FIG. 2 is a sectional view showing an ion source according to another embodiment of the invention. Third
The figure is a cross-sectional view showing an example of a conventional ion source. 2... Vacuum container, 6... Electrode, 10... Lid, 1
6...First lining plate, 18...Second lining plate, 10...Plasma generation chamber, 26...Inner cylinder.

Claims (1)

[Claims] 1. A first lining plate provided inside the cylindrical vacuum container at the same potential as the vacuum container and thermally insulated therefrom;
An electrode for extracting the ion beam is provided near one opening of this vacuum container, and an electrode is provided inside a lid for closing the other opening of this vacuum container at the same potential and thermally insulated from it. In an ion source in which a plasma generation chamber is configured by a second lining plate, the lid and the second lining plate are sized so that they can be placed inside the first lining plate,
and this lid is attached to an inner cylinder that cooperates with the lid to close the other opening side of the vacuum container and is large enough to be placed inside the first lining plate, and this inner cylinder is replaceable or movable;
An ion source characterized in that the positions of the lid and the second lining plate are thereby made variable, thereby making the surface area of the portion of the first lining plate that constitutes the plasma generation chamber variable.