JPS58192249A - Liquid metal ion source of high-frequency induction heating type - Google Patents

Abstract

PURPOSE:To increase the life of an ion source, and enable an ionized matter to be efficiently heated and molten by heating an ionized matter reservoir by means of a high-frequency induction heating means. CONSTITUTION:NiB, an ionized matter 1, is contained in a reservoir 4. NiB is molten and supplied to the pointed end of a tip 2 which protrudes from the end of the reservoir 4, and a voltage of over 5kV is applied across the tip 2 and a lead-out electrode 8 so as to draw an NiB ion beam 7 from the pointed end of the tip 2. Here, heat used for melting NiB is supplied from Joule heat produced by a surface current generated on the surface of the reservoir 4 by applying a high frequency to a work coil 9. Since the reservoir 4 is directly heated in high- frequency induction heating, thermal efficiency is improved and the ionized matter 1 having a high melting point (melting point, 110 deg.C) such as NiB can be relatively easily molten compared to current conduction heating.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ionized substance melting means for a solid metal ion source, and more particularly, to an ion source using high frequency induction heating means as the ionized substance melting means.

Conventionally, in liquid metal ion sources, electrical heating means have been used to melt the ionized substance.

FIGS. 1(a) and 1(b) show how ionized substances are melted in an IJ bath by a conventional electrical heating means. FIG. 1(a) shows the structure of a chip portion of a liquid metal ion source which is very simple. In this ion source, the support part 3 of the ion-emitting chip 2 is heated with electricity to melt the ionized substance 1 in a bath. A disadvantage of this ion source is that the ionized material 1 cannot be stored in the device. Further, when attempting to dissolve an ionized substance with a high melting point, it is necessary to flow a large flow of large 'fL through the support part 3, which may cause the support part 3 to break. The diameter of the support part 3 should be increased to prevent breakage, but it would be better to make the support part 3 into a trunk shape, but in that case, a larger current would be required.

FIG. 1(b) shows the cross-sectional configuration of the tip of a liquid metal ion source sold by Dubiliers of England. This ion source is provided with a reservoir 4 for the ionized substance 1 to extend the life of the ion source. In this ion source, the outside of the reservoir 4 is covered with a cylinder 6 made of an insulating material.
A heater 5 is wound around it, and the ionized substance 1 is melted by heating with a W wire. When attempting to melt the ionized substance in a bath using this ion source, a large current is required for the ionized substance having a high melting point. Further, in this ion source, heat is conducted from the heater 5 to the insulating material part 6 and further to the reservoir part 4 to heat the ionized substance 1, and the heating efficiency is not good.

In both of the above-mentioned types of ion sources, the power-conducting heat method requires a large current to melt the ionized substance with a high melting point, and a Electric wires that can handle large currents are required. In addition, the type with the reservoir 4 has a good 710 heat efficiency.

An object of the present invention is to provide a liquid metal ion source with an ionized material reservoir capable of storing a sufficient amount of ionized material, to prolong the life of the ion source, and to efficiently heat and melt the ionized material. It is an object of the present invention to provide a source of molten metal ions that can be used.

In order to achieve the above object, in the present invention, the ionized substance reservoir is heated by one ^1 wave induction heating means. The t￥f tax collection structure of the present invention is as follows:
Since it is high-frequency induction heating, the ionized 1-layer constriction part can be directly heated, and the heating efficiency is high. Therefore, it is possible to easily heat the reservoir, which is larger than the conventional ionized material reservoir, and the life of the ion source can be extended by storing a large amount of ionized material. In addition, conventionally, because the melting point is low,
It is now possible to melt ionized substances in a bath, which was considered difficult to melt in practice because the current required by current heating means was too large.

Hereinafter, the present invention will be explained according to examples.

Part 2 r Sub n 1 NIB I/O which is an embodiment of the present invention
This shows the source of the information. NiH, which is an ionized substance, is present in the reservoir 4. This NIB is melted and supplied from the tip of the reservoir 4 to the tip of the hanging chip 2, and a high voltage of 5KV or more is applied between the tip 2 and the extraction electrode 8, and the NIB ion beam is beamed from the tip of the tip 2. Pull out 7. Heat for melting the NIB is supplied from Joule heat generated by a surface current generated on the surface of the reservoir 4 by applying a high frequency to the work coil 9. ^ Frequency induction heating has good thermal efficiency because it directly heats the reservoir 4, and N
Melting of an ionized substance 1 with a high melting point (melting point: 110C) such as IB can be performed relatively easily compared to electric heating. At this time, the contact area of the height-determining ceramic insulator 13 that fixes the cartridge-type reservoir 4 and the MO screw 11 for chip axis alignment with the reservoir 4 is made as small as possible to prevent heat by thermal conduction. I run away less. In addition, the shielding cylinder IO is used to protect the area around the reservoir 4, thereby suppressing the escape of heat due to thermal radiation and preventing a rise in temperature around the ion source. The bottom surface of this shielding cylinder IO was set at the same height as the tip of the tip 2, and was designed to function as a control electrode for finely controlling the ion current. Furthermore, the reservoir 4 and the chip 2 were made of carbon material. This is because when the reservoir 4 and the chip 2 are made of conventional high-melting point metals such as W and MO, NiB, which is the ionized substance 1, reacts with the entire area of these parts, shortening the life of this part. For example, the lifetime Vi of the W chip is within 1 minute. Therefore, a carbon material with low reactivity with NiB was used for this part, but in this ion source, the reservoir part 4 was made by sintering graphite and the feed body was made by sintering, and the tip 2 was made by sintering graphite. Make sure to use one with glassy carbon attached to the body light and electrolytically polished to a radius of curvature of about 1 μm at the tip. With this ion source, effective heating is possible using high-frequency induction heating means, so NiB
The temperature of NiB can be raised to a sufficiently high level above the melting point, and even if the temperature decreases, the NiB can be sealed in the cartridge-type reservoir 4 and the lower end of the reservoir 4 exposed to the outside can be evaporation of NiB due to temperature rise is also reduced. Therefore, this ion source was able to operate at high temperatures and was able to extract the NIB ion beam 7 with good stability.

In order to reduce transmission loss and to avoid consuming more power than necessary, the heating frequency f is generally set at a critical frequency fc.
From the above, it is desirable to choose about 5 times that amount. This critical frequency fC is defined by the following equation.

f c = 12&5-1 (Hz) μat Here, ρ is the specific resistance of the heated object (μΩ-z), μ is the relative magnetic permeability of the heated object, and aF′i is the radius of the heated object (cm ) . Now, the object to be heated is graphite, and ρ=1000/
JΩ(?Fl!% p ” 1 % Also, a =
It is set to 0.25 cm. Then, fc =ZIMH
Becomes z. Therefore, the appropriate heating frequency f is 2MHz −1
The range is 0MHz. However, in order to avoid communication interference, and because a power supply with that specification was commercially available, the heating frequency was set to the industrially allocated frequency of 13.56MHz.
It was used. If the frequency is high, a little more power is required, but the penetration depth of the surface current flowing through the graphite surface remains, and heating efficiency improves, so 13.56 M
Even when HE was used, there was no problem in heating.

According to the present invention, since the ionized substance l can be efficiently heated, the ionized substance l having a melting point of more than tooot:'
It can also be easily heated to a temperature at which the ion beam 7 can be stably extracted, which is effective in improving the stability of the liquid metal ion source. Friend, by making the reservoir 4 of the ionized substance 1 into a cartridge type, when the ionized substance 1 runs out and you want to change to another ionized substance 1, you only need to replace the cartridge type reservoir 4, which makes the work easier. Become. Furthermore, by using a carbon material for the reservoir 4 and the tip 2, ionized substances such as conventional W, MO, etc. have high reactivity with those metals, and it is impossible to extract the ion beam 7'5r. The ion beam 7 can now be extracted from the ion beam, which is effective in expanding the ion species.

[Brief explanation of drawings]

＠Figure 1 shows a heating method using a conventional electrical heating method.
This figure shows a type of liquid metal ion source that melts an ionized substance using a liquid metal ion source. Fig. 2 is a block diagram of a liquid metal ion source using high frequency induction heating means according to the present invention. 1... Ionized substance, 2... Chip, 3... Support part, 4... - Reservoir, 5... Heater, 6... Insulator tube, 7... Ion beam, 8... Extraction electrode, 9... Work coil, lO... Shield cylinder, 1
1...MO screw! 2... Ceramic insulator, 13.
...Ceramic insulator, 14...Ceramic insulator, 15
...Support rod. Agent Patent Attorney Toshiyuki Usuda 1 Cause (α) (b) 2nd Portion Continued from page 1 0 Inventor Kenko Miyauchi, Hitachi, Ltd., Institute of Industrial Science, 292 Yoshida-cho, Totsuka-ku, Yokohama

Claims (1)

[Scope of Claims] 1. A liquid metal ion source comprising an ionized substance reservoir, a heat source for melting the ionized substance, an ion emission chip, and an ion extraction electrode, wherein the heat source for melting the ionized substance comprises high-frequency induction heating means. A high-frequency induction heating liquid metal ion source featuring: 2. The high-frequency induction heating type liquid metal ion source according to claim 1, wherein the chip and the reservoir are provided in a shield that almost completely covers them. 3. The high-frequency induction heating type liquid metal ion source according to claim 1, wherein the ionized substance reservoir is configured in an IJ type. 4. The high frequency induction heating liquid metal ion source according to claim 1, wherein the ionized substance reservoir and the ion emitting tip are made of carbon.