JPH06295693A - Ion source device - Google Patents

Abstract

PURPOSE:To achieve a long life of a thermal filament by setting a potential of a cover disposed close to as the filament to be the same potential of a minus terminal of a filament. CONSTITUTION:A cover 19 comprising a high-fusing point material of tungsten, tantalum, etc., is disposed close to a thermal filament 5, and a potential of the cover 19 is set to be the same potential of a minus terminal 4 of the filament 5. The potential of the cover 19 is thus set to be lower than the potential at any position in the filament 5, ions in plasma are easy to flow to the cover 19, the ions flowing to the filament 5 are dispersed in the cover 19, and partial consumption of the filament 5 can be reduced, thereby its life can be elongated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion source device using a hot filament.

[0002]

2. Description of the Related Art A conventional ion source device has a structure shown in FIG. In the figure, 1 is a cylindrical housing, 2 is an arc chamber formed in the housing 1, 3 is a cover plate closing one end of the housing 1, 4 is an arc chamber 2 penetrating the cover plate 3.
Two current introducing terminals 5 introduced into the inside are hot filaments whose both ends are attached to the tips of both current introducing terminals 4,
It becomes a thermionic emission source as a cathode. Reference numeral 6 is a filament power supply for heating the filament 5 connected to the bases of both power supply introduction terminals 4, 7 is a cylindrical anode arranged in the arc chamber 2, and 8 is a rare anode such as argon in the arc chamber 2. It is a gas inlet for introducing an ionized gas of gas.

The reference numeral 9 designates a porous electrode system attached to the other end of the housing 1 for extracting an ion beam, and the arc chamber 2
It is composed of a side acceleration electrode 10, a middle deceleration electrode 11, and an outer ground electrode 12.

Reference numeral 13 denotes an arc power supply whose negative pole is connected to the negative pole of the filament power supply 7 and applies an anode voltage to the anode 7. Reference numeral 14 denotes a resistor 15 through a resistor 15.
An acceleration power supply for applying a positive acceleration voltage to 0, and a deceleration power supply for applying a negative voltage to the deceleration electrode 11.

The filament 5 is held at a high temperature by resistance heating by the filament power source 6 and emits thermoelectrons e, and the discharge between the cathode filament 5 and the anode 7 causes the gas inlet 8 to enter the arc chamber 2. Plasma 17 of the ionized gas introduced into the
Plasma 1 is generated by the beam extraction action of the porous electrode system 9.
The ion gas in 7 becomes an ion beam and is extracted.

[0006]

In the case of the above-mentioned conventional apparatus, since the filament 5 serves as the cathode, the plasma 1 is always used.
When the filament atoms are sputtered by the impact of the ions in 7, the filament 5 becomes thin, the resistance value of the thin portion increases, the temperature rises, and the filament 5 melts when it reaches the melting point. In particular, the minus side of the filament 5 is greatly consumed due to the potential difference.

Further, in order to extract an ion beam having a large current density, a high plasma density is required, so that there is a problem that the filament 5 is heavily consumed and the life of the filament 5 is shortened. The present invention has been made in consideration of the above points, and an object of the present invention is to provide an ion source device designed to extend the life of a filament.

[0008]

In order to solve the above-mentioned problems, the ion source device of the present invention is an ion source device using a hot filament, and a cover made of a high melting point material such as tungsten or tantalum is provided in the vicinity of the filament. And the potential of the cover is set to the same potential as the minus terminal of the filament.

[0009]

In the ion source device of the present invention constructed as described above, a cover made of a high melting point material such as tungsten or tantalum is provided in the vicinity of the hot filament, and the potential of the cover is the same as that of the minus terminal of the filament. Therefore, the electric potential of the cover is lower than the electric potential of any position of the filament,
Ions in the plasma can easily flow into the cover, the ions flowing into the filament can be dispersed in the cover, the impact on the filament can be reduced, and the partial wear of the filament can be reduced. The life can be extended.

Further, since the cover is arranged in the vicinity of the filament, the temperature rises due to the heat radiation from the filament and the energy of the inflowing ions, and thermions can be emitted from the cover. Therefore, more thermoelectrons can be emitted with the same filament current than before, plasma with higher density can be generated, filament current can be reduced, and it can be used until the filament wire diameter becomes thinner. Therefore, the life can be extended.

[0011]

EXAMPLES Examples will be described with reference to FIGS. 1 to 5. In these figures, the same symbols as those in FIG. 6 indicate the same or corresponding ones. First, FIG. 1 showing the first embodiment.
In FIG. 2, 18 is a screw hole formed on the tip end surface of the current introducing terminal 4, 19 is a band-shaped cover made of high melting point metal such as tungsten or tantalum and bent at a right angle, and 20 is a base part of the cover 19. The formed through hole, 21 is a spacer, and 22 is a screw, which is inserted through the trapezoidal portion at one end of the filament 5, the spacer 21, and the through hole 20 and is screwed into the screw hole 18 of the terminal 4 on the minus side, 4, the filament 5 and the cover 19 are mounted, the cover 19 is set to the same potential as the negative side terminal 4, the cover 19 is located inside the filament 5, and the tip of the cover 19 is placed between the folded portions of the filament 5. It is arranged so that it can be inserted into.

It should be noted that the spacer 21 is interposed between the filament 5 and the cover 19, and the cover 19 serves as the filament 5.
It prevents contact with the middle part of the. Further, the screw 22 of the positive side terminal 4 is inserted into the bowl-shaped portion at the other end of the filament 5 and screwed into the screw hole 18 of the positive side terminal 4.

Next, referring to FIG. 3 showing the second embodiment,
1 and 2, the cover 19 is disposed outside the filament 5 and the screw 22 is provided in the insertion hole 2 of the cover 19.
0, through the spacer 21 and inserted into the dough-like portion of the filament 5.

Next, in FIG. 4 showing the third embodiment, the shape of the cover 19 is drastically different, and a horizontal portion is formed by bending the base portion of the inverted L-shaped plate located in the vertical direction. 23
Is formed, and the insertion hole 20 is formed in the horizontal portion 23,
A cover 19 is arranged on the side of the filament 5.

Next, in FIG. 5 showing the fourth embodiment, a step is formed in the cover 19 without using the spacer 21 and the cover 19 is formed.
This prevents contact between the filament 5 and the intermediate portion of the filament 5. A step may be formed on the filament 5 as shown by the one-dot chain line.

Further, in the above embodiment, the cover 19 is screwed to the terminal 4 together with the filament 5, but the present invention is not limited to this, and the cover 19 may be supported by another means so as to have the same potential as the minus terminal 4. Good. Furthermore, the cover 19 may have a linear shape instead of a plate shape.

Further, by disposing the cover 19 near the minus side of the filament 5, the inflow of ions into the minus side of the filament 5 can be reduced.
Since the amount of ions flowing in can be adjusted by the area of the cover 19, the amount of ions flowing into the plus side and minus side of the filament 5 can be adjusted to the same degree. Therefore, the entire filament 5 can be consumed almost uniformly, and the partial temperature rise due to the partial consumption of the filament 5 can be avoided,
The life of the filament 5 can be extended.

[0018]

Since the present invention is constructed as described above, it has the following effects. In the ion source device of the present invention, the cover 19 made of a high melting point material such as tungsten or tantalum is provided in the vicinity of the hot filament 5, and the potential of the cover 19 is set to the same potential as the minus terminal 4 of the filament 5. Is lower than the electric potential at any position of the filament 5, ions in the plasma can easily flow into the cover 19, and the ions flowing into the filament 5 can be dispersed in the cover 19, and the impact on the filament 5 Is reduced, filament 5
It is possible to reduce the partial consumption of, and to prolong the service life.

Further, since the cover 19 is arranged in the vicinity of the filament 5, the temperature rises due to the heat radiation from the filament 5 and the energy of the inflowing ions,
Thermal electrons can also be emitted from the cover 19. Therefore, more thermoelectrons can be emitted with the same filament current as compared with the conventional one, a higher density plasma 17 can be generated, the filament current can be reduced, and it can be used until the filament wire diameter becomes thinner. It becomes possible and the life can be extended.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment of the present invention.

FIG. 2 is a partially cutaway front view of FIG.

FIG. 3 is a partial cutaway front view of a second embodiment of the present invention.

FIG. 4 is a partial cutaway front view of a third embodiment of the present invention.

FIG. 5 is a partial cutaway front view of Embodiment 4 of the present invention.

FIG. 6 is a schematic configuration diagram of an ion source device.

[Explanation of symbols]

 4 terminal 5 filament 19 cover

Claims (1)

[Claims] 1. An ion source device using a hot filament, wherein a cover made of a high melting point material such as tungsten or tantalum is provided in the vicinity of the filament, and the potential of the cover is set to the same potential as the negative terminal of the filament. Ion source device.