JPS5911175B2 - ion source - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion source capable of obtaining a large-diameter, high-density ion beam.

Recently, with the development of ion implantation methods, it is expected that elements such as aluminum and titanium will be implanted into metal surfaces to improve corrosion resistance and wear resistance.

Needless to say, a dog-caliber, high-output metal ion beam is suitable for such ion implantation.

By the way, there are the following two types of typical ion sources for obtaining conventional metal ion beams.

One of them is an electron impact type ion source, which ionizes vapor obtained by heating and vaporizing a solid in an oven or the like, or gaseous compounds such as metal chlorides by electron impact.

The other is a sputter type ion source, in which a solid (target) is bombarded with ions in the plasma within the ion source, and the sputtered particles are ionized in the plasma.

However, with any of the ion sources, only an ion beam with a small diameter of 10 mm or less can be obtained.

The present invention has been made in view of these points, and includes disposing a plate-shaped or rod-shaped anode in an evacuated chamber having an inert gas supply port, disposing a cathode having an air gap parallel to the anode, A means for forming an electric field between the cathode and the anode and a magnetic field in the air gap of the cathode is provided, the material around the air gap is made of a metal to be ionized, and a large-diameter, high-density ion beam can be obtained. A novel ion source is provided.

FIG. 1 shows an ion source showing an embodiment of the present invention.

In the figure, reference numeral 1 denotes an ion source outer cylinder, and a plate-shaped anode 2 made of a non-magnetic material such as stainless steel is provided approximately in the center of the cylinder and supported by an insulator 3.

A cathode 4 made of pure iron is provided below the anode and parallel to the anode.

The cathode is made up of two upper and lower plates 4 b t 4 c via a connecting body 4 a such as a shaft, just like a reel, and the respective plates are integrated by the shaft to form a magnetic circuit. Approximately ring-shaped gaps 5a, 5b, 6a, and 6b are provided approximately halfway between the center and the ends, and gaps 5a, 5b, 6a, and 6b are provided between the respective ends of the upper plate 4b and the lower plate 4c, for example. A ring-shaped permanent magnet 7 or an electromagnet is sandwiched, with the N (S) pole in contact with the upper plate and the S (N) pole in contact with the lower plate.

Further, the ring-shaped regions 8 and 9 around the gaps 5a and 5b of the upper plate 4b of the cathode are made of a metal material which becomes a source of the ions to be obtained (see FIG. 2).

Incidentally, a ring-shaped metal which is a source of the metal ions to be obtained may be placed on the ring-shaped regions 8 and 9.

Further, the ring-shaped regions 8 and 9 are partially made of non-magnetic material 17A,
They are connected by 17B.

A space surrounded by the cathode and the ion source outer cylinder 1 serves as a plasma generation chamber 10.

11 is an external cylinder for inert gas such as argon gas (
This is a gas leak pipe for introducing the gas into the plasma generation chamber 10 from (not shown), and is provided to penetrate the wall of the ion source outer cylinder 1 from the outside.

Below the lower plate 4c of the cathode 4, there is an extraction electrode 12 having approximately ring-shaped holes 12a and 12b (similar in shape to the holes of the cathode 4) in the middle between the center and the ends.
is provided.

A positive potential is applied to the anode 2 by a power source 13 with respect to the cathode 4, and a positive voltage is applied to the cathode with respect to the extraction electrode 12 by a power source 14.

In such an ion source, an anode 2 and a cathode 4
An electric field plate is formed between the cathode 4 and the gap 5a of the cathode 4.
A magnetic field Bo is generated in 5b by the magnet 7.

That is, an electric field Eo and a magnetic field B exist near the gaps 5a and 5b.

are orthogonal. Since inert gas (argon) is introduced into the plasma generation chamber 10 from the gas leak pipe 11,
Plasma is generated between the anode 2 and cathode 4 in the chamber.

Then, ions in the plasma are transferred to the upper plate 4b of the cathode 4.
collide with

This collision is particularly caused by the gap 5a, - of the upper plate body 4b.
5b, that is, in the ring-shaped areas 8 and 9.

Due to this collision, secondary electrons are generated mainly from the ring-shaped regions 8 and 9, and at the same time, the metal particles forming the ring-shaped regions are ejected into the plasma.

As shown in Figure 3, the secondary electrons are z = A(1-c
osωt), x=A(ω1-sinωtX However, it moves.

This movement is E in the Z direction. and B in the y direction. This is a motion that moves in a cycloidal curve in a direction (X direction) perpendicular to each of the directions.

The cycloidally moving electrons collide with neutral gas particles in the plasma and metal particles ejected from the ring-shaped regions 8 and 9, and ionize the neutral gas particles and metal particles.

The cycloidally moving electrons have a long movement distance,
The probability of collision with the neutral gas particles or metal particles is extremely high, and high-density ions are generated.

The high-density ions generated in the vicinity of the gaps 5a and 5b in this manner are extracted as a beam through the holes 12a>12b of the extraction electrode 12.

Incidentally, as shown in FIG. 4, small holes 1 6 a , 1 6 b , i corresponding to the gaps are formed in the upper plate 4 b of the canard 4 .
6c, 16a, . . . metal 15 may be fitted or placed.

According to the present invention, a high-density ion beam can be extracted.

Furthermore, a large diameter ion beam can be extracted from the shape of the gap.

[Brief explanation of drawings]

Fig. 1 shows an ion source according to an embodiment of the present invention, Fig. 2 shows some details thereof, Fig. 3 shows the trajectory of electrons in the plasma generation chamber of the ion source of the invention, and Fig. FIG. 4 shows another embodiment of the upper plate of the cathode. 2: anode, 4: cathode, 4b: upper plate, 5a,
5b, 6a, 6b=gap, 7: permanent magnet, 8,
9: IJ ring-shaped area, 10: Plasma generation chamber, 11
: Gas leak pipe, 12: Extraction electrode, Eo, Bo
: Electric field magnetic field.

Claims (1)

[Claims] 1. A plate-shaped or rod-shaped anode is arranged in an evacuated chamber having an inert gas supply port, a cathode having an air gap is arranged parallel to the anode, an electric field is formed between the cathode and the anode, and the cathode An ion source comprising means for forming a magnetic field in an air gap, and a material around the air gap is made of a metal to be ionized.