JPH07272657A - Ion source device - Google Patents

Abstract

PURPOSE:To lengthen the life of a filament within a high density plasma by disposing a specified auxiliary body in the vicinity of the filament and specifying the potential of this auxiliary body in an ion source device using a thermal filament. CONSTITUTION:In an ion source device using a thermal filament 3, an auxiliary body 9 made of a high melting point material such as W, Ta and the like is disposed in the vicinity of the filament 3 and the potential of the auxiliary body 9 is made lower than that of the filament 3. Thus, ions within plasma are caused to easily flow into the auxiliary body 9, impacts on the filament 3 are reduced, wearing of the filament is reduced realizing a long life.

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 which uses a hot filament to extend the life of the filament.

[0002]

2. Description of the Related Art A conventional ion source device is shown in FIG. In the figure, 1 is an arc chamber, 2
Is two current introducing terminals introduced into the arc chamber 1,
3 is a thermal filament made of W or the like, which is provided inside the arc chamber 1 and has both ends connected to both current introducing terminals 2, and 4 is a filament which is provided outside the arc chamber 1 and has both ends connected to both current introducing terminals 2. The power source 5 is an arc power source whose positive pole is connected to the arc chamber 1 and whose negative pole is connected to the negative pole of the filament power source 4, 6 is an ion extraction electrode, and 7 is plasma.

A filament heating current is supplied to the filament 3 by the filament power source 4, an arc voltage is applied by the arc power source 5, the thermoelectrons emitted from the filament 3 are accelerated, and the gas in the arc chamber is ionized. Plasma 7 is generated.

[0004]

In the case of the above-mentioned conventional device, since the filament serves as the cathode, the filament is
The filaments are constantly sputtered by the impact of the ions in the plasma, the filaments become thin, and when the filaments become thin, the resistance value of that portion increases, the temperature rises, and when the filament reaches the melting point, it melts. In particular, the negative side of the filament is greatly consumed due to the potential difference, and the life of the filament is shortened.

On the other hand, when extracting an ion beam having a large current density, a high plasma density is required. For that purpose, it is necessary to increase the arc voltage or the filament current. Now, when the arc voltage is increased, the energy of the thermoelectrons accelerated by the arc voltage increases. Moreover, when the filament current is increased, the temperature of the filament is increased, and more thermoelectrons are emitted. for that reason,
In either case, higher density plasma can be generated.

However, when the arc voltage is increased, the ions collide with the filament with energy equivalent to the arc voltage, so that the filament is more consumed by sputtering. In addition, if the operating temperature of the filament is increased, the filament is apt to melt when it is consumed. That is, in any case, when trying to obtain a high-density plasma, there is a problem that the filament is heavily consumed and the life of the filament 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 in which the life of a filament in a high density plasma is extended.

[0007]

In order to solve the above problems, the present invention provides an ion source device using a hot filament, in which an auxiliary body made of a high melting point material such as W or Ta is arranged in the vicinity of the filament. However, the electric potential of the auxiliary body is lower than the electric potential of the filament.

[0008]

In the ion source device of the present invention configured as described above, the auxiliary body made of a high melting point material is arranged in the vicinity of the filament, and the potential thereof is lower than the electric potential of the filament. It is easier for the filaments to flow into one direction, the impact on the filaments is reduced, the filaments are less consumed, and the life is extended.

Further, since the auxiliary body is 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 the auxiliary body also emits thermoelectrons. Therefore, more electrons will be emitted with the same filament current, and a higher density plasma can be generated. Therefore, the filament current can be reduced, and the filament current can be reduced until the filament wire diameter becomes thinner. Can be done and the life is extended. further,
The electrons emitted from the auxiliary body have energy of the difference between the plasma potential and the potential of the cover. Therefore, by lowering the potential of the auxiliary body, electrons with larger energy are emitted. Therefore, since the number of ions that can be ionized by the collision of these electrons increases, high-density plasma can be generated, and the filament life is extended for the same reason as above.

[0010]

EXAMPLES Examples will be described with reference to FIGS. 1 and 2. In these figures, the same reference numerals as those in FIG. 3 indicate the same or corresponding ones. (Embodiment 1) In FIG. 1 showing Embodiment 1, the following is added to FIG. Reference numeral 8 is a terminal for an auxiliary body introduced into the arc chamber 1 between both current introduction terminals 2, 9 is an auxiliary body made of a high melting point material such as W or Ta provided near the filament 3 in the arc chamber 1. Is auxiliary body 9
A screw fixing the base portion of the auxiliary body terminal 8 to the auxiliary body terminal, 11 is an auxiliary body power source, the negative pole is connected to the auxiliary body terminal 8,
The positive pole is connected to the negative pole of the filament electrode 4, and the potential of the auxiliary body 9 is lower than the potential of any part of the filament 3.

The auxiliary body 9 is shown in the vicinity of the U-shaped filament 3, that is, between the U-shaped portions of the filament 3, but it may be located at the side of the filament 3 and the filament 3 and the ion. It is desirable that it is not between the extraction electrode 6. The auxiliary body 9 may have any suitable shape such as a linear shape, a rod shape, a ribbon shape, or a plate shape.

(Embodiment 2) FIG. 2 showing Embodiment 2 is different from FIG. 1 in that there is no auxiliary body power source 11, the auxiliary body terminal 8 is connected to the negative pole of the arc power source 5, and the filament power source is used. 4 is the point where the first resistor 12 and the second resistor 13 are respectively connected between the negative pole of the arc power source 5 and the positive pole and the negative pole of the arc power source 5, and the potential of the auxiliary body 9 is as shown in FIG.
As in the case of, the potential of any part of the filament 3 is lower.

[0013]

Since the present invention is configured as described above, it has the following effects. In the ion source device of the present invention, the auxiliary body 9 made of a high melting point material is arranged in the vicinity of the filament 3 and the electric potential thereof is lower than the electric potential of the filament 3, so that the ions in the plasma easily flow into the auxiliary body 9. The impact on the filament 3 is reduced, the consumption of the filament 3 is reduced, the life of the filament 3 can be extended, and high-density plasma can be generated while suppressing the consumption of the filament 3.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a conventional example.

[Explanation of symbols]

 3 filament 9 auxiliary body

Claims (1)

[Claims] 1. An ion source device using a hot filament, wherein an auxiliary body made of a high melting point material such as W or Ta is arranged in the vicinity of the filament, and the potential of the auxiliary body is made lower than the potential of the filament. Source device.