JPS61214330A - Liquid metal ion source - Google Patents

Abstract

PURPOSE:To reduce the evaporation rate of an ionization substance so as to improve the ionic radiation of a liquid metal ion source by using an ionization substance reservoir which consists of a pipe fixed to a current-feeding-type heater and using an emitter which penetrates the reservoir. CONSTITUTION:In an ion source for an ion microbeam device or a similar device, an ionization substance 1 is heated and molten by a heater 2 to supply molten substance to the pointed end of an emitter 3 and then a lead-out electrode 4 is used to produce an ion beam 5 from the molten substance. A reservoir 12 for the ionized substance 1 consists of a funnel-like pipe made of tantalum or similar material and is fixed to a current-feeding-type heater 2 by means of an aluminum powder 13 containing a binder. The ion beam 5 is discharged from the pointed end of the emitter 3 which penetrates the reservoir 12. Since molten ionization substance contained in the reservoir 12 evaporates only from the end surfaces, it is possible to produce ions for a long time by reducing the evaporation rate of the molten ionization substance.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is an ion source for an ion microbeam device used for fine ion implantation, ion exposure, ion processing, etc. Relating to liquid metal ion sources.

[Background of the invention]

An example of the basic configuration of a conventional liquid metal ion source is published in the journal Vacuum Science and Technology (J
, Vac, Sci, Technol, ) AZ (198
2) It is as described in 1365, which is shown in FIG. 1, and the principle of operation will be explained. A substance 1 to be ionized is heated and melted by a heater 2 and supplied to the tip of an emitter 3. A high voltage of several kV is applied between the emitter 3 and the extraction electrode 4, a strong electric field is applied to the tip of the emitter, and the substance to be ionized is extracted from there as ions 5 by field evaporation. It is important to be able to stably extract the desired ion beam.

In this conventional example, when the vapor pressure of the molten ionized substance is high, the proportion of the exposed surface area of the ionized substance is large;
The ion source life is shortened due to the evaporation of ionized substances from the ion source, and the electrical insulation deteriorates due to the evaporated substances depositing on the insulator between the electrodes that make up the ion source. There were problems such as the instability of the beam.

[Purpose of the invention]

An object of the present invention is to provide a highly reliable liquid metal ion source with extremely stable ion emission characteristics.

[Summary of the invention]

In order to achieve the above object, the present invention includes a reservoir section that melts and holds a substance to be ionized, and a reservoir section that is arranged so as to emit ions of the molten ionized substance supplied from the reservoir section from its tip. In a liquid metal ion source consisting of an emitter and an extraction electrode that applies a high electric field between the emitter and extracts ions from the emitter tip, the needle-shaped emitter passes through a pipe that is a reservoir of ionized substances. The pipe is characterized in that it is fixed in contact with an electrical heating type heater.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. The ionizable substance in this example is gold.

The melting point of gold is 1063℃, and the vapor pressure at that temperature is approximately 2×1
0-''Pa.The emitter 3 is made into a needle-shaped tungsten wire with a diameter of 0.4 am, and the radius of curvature of the needle-like part at the tip is several μm.
2 is made of a tantalum pipe with an outer diameter of 1.5 amφ, a wall thickness of 50 um, and a length of 5 mm. A slit of 2 mm in length and 4 parts is cut into the end face on the base side of the emitter, and that part is a funnel. It is expanded into a shape. This funnel-shaped extension is provided to facilitate the replenishment of 0.3 to 1 ml of bulk ionized material. The pipe-shaped reservoir 12 is fixed in contact with the electrical heating type heater 2 with alumina powder 13 containing a binder. In this embodiment, the heater 2 is a plate-shaped heater made of carbon material and having a length of about 0.5 mm and a width of 2.5 mm. By applying power of about 60 W to the heater 2 from the heating power source 9 in a vacuum, the reservoir 12 can be heated to about 1100° C., and the ionized substance 1 can be kept in a molten state. From the emitter tip sufficiently wetted with the molten ionized substance, a negative potential of -5 to -9k is applied to the emitter 3 from the extraction power source 10 to the extraction electrode 4.
By applying V, the ion beam 5 can be extracted.

The pipe-shaped reservoir 12 is fixed in contact with the heater 2 by heaping up alumina powder 13 containing a binder.
This is to allow the conduction to occur.

In this embodiment, the evaporation surface of the molten ionized substance 1 is limited to both end surfaces of the pool in the pipe-shaped reservoir 12, and is smaller than that of the conventional ion source (see FIG. 1) to about 115.

Therefore, the amount of evaporation is small, and the life of the ion source is about 4 to 5 times longer than when the same amount of ionized material is loaded. Furthermore, the amount of evaporated substances deposited on the insulator between the electrodes is reduced, and the deterioration of electrical insulation caused by this can be greatly reduced, making it possible to emit stable emitted ion current for a long time.

〔Effect of the invention〕

According to the present invention, ions can be extracted stably for a long time, and the performance and reliability of the ion source can be improved.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of a conventional liquid metal ion source, and FIG. 2 is a diagram showing a liquid metal ion source which is an embodiment of the present invention. 1...Ionized substance, 2...Heater, 3...Emitter.

Claims (1)

[Claims] 1. A reservoir that melts and holds the substance to be ionized;
an emitter arranged to emit ions of the molten ionized substance supplied from the reservoir from its tip; and an extraction electrode that applies a high electric field between the emitter and extracts ions from the emitter tip. A liquid metal ion source configured, wherein the emitter passes through a pipe that is the reservoir of ionized substance,
A liquid metal ion source characterized in that the pipe is fixed in contact with an electrical heating type heater.