JPS5846542A - Field emission liquid metal aluminum ion gun and its manufacture - Google Patents

Abstract

PURPOSE:To obtain an Al ion beam of high luminance stable for a long time and narrow an energy width further increase angular current density, by constituting a needle-shaped emitter with either conductive boride or conductive compound boride or conductive carbide. CONSTITUTION:A metallic fine wire of diameter 0.15-0.3mm.phi made of Ti, Zr, etc. is spot welded to conductive supporting parts 8, extensibly fixed through an insulating holder 7, to build up the original form of an Al ion gun having a heating support unit and needle-shaped metallic emitter unit. The point end of the needle-shaped metallic emitter unit 10 is formed to a needle shape of radius of curvature 1-10mum by the method of electrolytic sharpening or chemical polishing and the like. And then the metallic wire of Ti, Zr, etc. of the heating support unit 9 and the needle-shaped metallic emitter unit 10 is processed with inversion to obtain a heating support unit 11 and needle-shaped emitter unit 12 inverted into boride and carbide of TiB2, ZrB2, TiC, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a field emission type liquid metal ion gun that emits a high-intensity aluminum (At) ion beam, and a method for manufacturing the same.

A field emission type liquid metal ion gun using a needle-shaped metal emitter is well known as a high-intensity ion gun. 1st
The figure shows a configuration diagram of a field emission type liquid metal ion gun. The needle-shaped metal emitter 1 is a conductive thin wire (~0.2 mmφ
), its tip radius of curvature is 1 to 10μ
It is m. Therefore, when a voltage is applied between the metal emitter 1 and the extraction electrode 2 by the power source 6, a high electric field is applied to the tip of the metal emitter 1. This metal emitter 1 is spot welded to a heating support 4. When the ion emitting metal 5 is melted and adhered to the heating support 4 and the heating support 4 is heated to a high temperature using the heating power source 6, the metal 5 is melted and supplied to the tip of the metal emitter 1. Ru.

At this time, the needle-shaped metal emitter 1 covered with liquid metal 5
When the tip electric field reaches a certain threshold, the electrostatic force applied to the liquid metal surface exceeds the contraction force due to the surface tension of the liquid metal,
The liquid metal has a conical shape called a Taylor cone. At the same time, the liquid metal's evaporation electric field is reached at the tip of the cone, and ion emission begins. However, the needle emitter of the conventional field emission type liquid metal ion gun is W,
It was limited to metal emitters such as Ni and Ni-Cr. Therefore, highly reactive metals such as AL react with existing metal emitters, so a practical field emission type liquid metal At ion gun has not been realized.The present invention aims to eliminate this drawback by using At A field emission type liquid metal ion gun was developed by finding a needle-shaped emitter material that satisfies the conditions necessary for realizing an ion gun. That is, in the present invention, the needle emitter is made of either a conductive boride, a conductive composite boride, or a conductive carbide.

Hereinafter, the present invention will be explained in detail with reference to examples as shown in FIG.
Figs. a), fb) are basic configuration diagrams of an M ion gun according to an embodiment of the present invention, which uses a needle-like emitter manufactured by converting a high-melting point metal wire into boride or carbide. In FIG. 2, 7 is an insulating holder, 8 is a conductive support part, 9 is a heating support part, 10 is a needle-shaped metal emitter part, 11. j2 is a heating support portion and a needle-shaped emitter portion, which are respectively converted into boride or carbonized material. First, as shown in FIG. 2 (al), a thin metal wire such as Ti or Zr with a diameter of 0.15 to 0.5 mm is spot welded to the conductive support part 8 fixed through the insulating holder 7 to form a heating support part. Then, a prototype of a KT ion gun having a needle-shaped metal emitter part is assembled.The tip of the needle-shaped metal emitter part 10 is made into a needle shape with a radius of curvature of 1 to 10 μn1 by electrolytic polishing or chemical polishing. Support part 9 and needle-shaped metal emitter part 1
0 Ti, Zr, etc. metal wires can be converted into TiB2. ZrB2. The heating support part 11 and the needle-shaped emitter part 12 are converted into borides and carbides such as TiC. Conversion methods include a solid-liquid reaction using a liquid as a reaction medium and a solid-gas reaction using a gas. Good (known. For example, as a solid-liquid reaction, N
By melting a2B4O7 and SiC in a crucible and immersing the al heating support part 9 and metal emitter part 10 in the crucible, it is converted into boride.On the other hand, as an example of a solid-gas reaction, The prototype At ion gun shown in FIG. 2(a) is held in a vacuum, and a gas such as Ar or H2 is introduced into it along with BCl2, B2H6, or C2H4,
When a current is passed through the heating support part 9 and the heating support part 9 and the metal emitter part 10 are heated to a high temperature, the heating support part 9
and the metal emitter portion 10 is converted to boride or carbide. Also, as a method similar to the latter, BN and the prototype ion gun shown in FIG. 2 are placed in an electric furnace at the same time and subjected to high-temperature treatment to convert it into boride. In addition, we have described a method of using a material to be converted as the generatrix of the heating support part 9 and the metal emitter part 10, but it is also possible to use Ti, Zr, Cr, etc. on a high melting point and strong core wire (for example, W, Mo, etc.). Needless to say, the ion gun may be constructed by performing the above-mentioned conversion treatment after melt coating.

FIGS. 3(a)-(cl) show another embodiment of the present invention, in which a field-emission liquid metal kl ion gun using a needle-like emitter made from a matrix of boride, composite boride, or carbide is shown. The basic configuration diagram is shown. In Fig. 3, 16 is a base material, 14 is a matrix for a needle-shaped emitter, 15 is a needle-shaped emitter part with an integrated heating part, and 16 is a connection part. The material of the base material 16 is , TiB2.
Borides such as ZrB and CrB2, T r 82 and M
or a composite boride such as TiC2 and TiC or TiB2 and BN, or a carbide such as TiC. From these base materials 16, the base mold 14 of the needle-shaped emitter part 1 is machined by electrical discharge machining 1.
After cutting by mechanical processing (diamond cutter, etc.) or ultrasonic processing, the tip curvature is polished to 1 to 10 μm K by grinding, electrolytic polishing, etc. 1. , to make a needle-like emitter. Thereafter, the needle-shaped emitter section 15 is connected to the conductive support section 8 penetrated through the insulating holder 7 by the connecting section 16 and at the same time is firmly fixed. In this way, a field emission type liquid metal At ion gun is constructed.

FIG. 2(b) and FIG. 3(c) are ion guns having basically the same configuration, except for the manufacturing method.

The acicular emitter material TiB2 used here. Borides such as ZrB2, composite borides containing Ti82, etc., and carbides such as TiC meet the essential requirements as a needle-shaped emitter of a field emission type liquid metal ion gun, namely (1) that the reaction with molten A/- proceeds. (2) good wettability with molten At, (3) electrical conductivity, (harder to undergo electric field evaporation than 41At, (5) low vapor pressure, (much higher melting point than 61At) , (7) It satisfies the conditions such as being able to be processed into a needle-shaped emitter. Therefore, as mentioned in FIG. 1, in FIG.
After melting and adhering the heating part to the integrated needle-like emitter part 15), the heating support part 11 and the needle-like emitter part 12 (
When the needle emitter section 15) is heated, AL is melted and supplied to the tip of the needle emitter section 12 (15). At this time, if a high voltage (5 to 10 kV) is applied between the extraction electrode 2 and the needle-shaped emitter section 12 (15), a high electric field will be applied to the tip of the needle-shaped emitter section 12 (15), and it will remain stable for a long time. A continuous At ion beam can be obtained.

FIG. 4 shows another embodiment of the present invention, and is a basic configuration diagram of a field emission type liquid metal M ion gun and an explanatory diagram of a method for manufacturing its needle-like emitter. In this example, a molten At metal reservoir is provided to enable long-life operation of an A4" ion gun. Figure 4(a) shows a high melting point metal thin wire (0.15~0.0
．． 3 mmφ) 17 into a boride or carbide acicular emitter 18 by conversion treatment.

That is, after the tip curvature of the thin metal wire 17 is set to 1 to 10 μm by electropolishing or chemical polishing, it is converted into a needle-shaped emitter 18 of boride or carbide by solid-liquid reaction or solid-gas reaction. FIG. 4(b) shows a method of manufacturing a needle-shaped emitter 21 from a base material 19 of boride, composite boride, or carbide. That is, from the base material 19 0.6 to 0.
Electric discharge machining 1 of a 7 mm square or cylindrical rod 20
The rod 20 is cut out by mechanical processing (diamond cutter, etc.), and the radius of curvature at the tip of the cut rod 20 is set to 1 to 10 μm by polishing or electrolytic polishing, thereby producing a needle-shaped emitter 21. Figure 4 fcl, (d) is
A basic configuration diagram of a field emission type liquid metal ion gun using the needle emitter 18 or 21 produced in this manner is shown. In FIG. 4(C), 22 is an At metal reservoir, 23 is a single-needle emitter support 24 is a heating resistance wire, and 25 is an insulating thermal conductor. A hole is provided at the tip of the At metal reservoir 22, and the needle-like emitter 18 or 21 protrudes from the hole through the metal reservoir 22 with a small gap (approximately 0.1 mm). With such a configuration, when At is placed in the At metal reservoir 22 and heated by passing a current through the heating resistance wire 24, the kl in the metal reservoir 22 becomes the insulating thermal conductor 25. is melted through. This molten At
is a needle emitter 18 or 2 protruding from the metal reservoir 22.
1 and is fed to its tip. Therefore, as explained in FIG.
If a high voltage is applied between
A high electric field is applied to the tip of 1, and an ion beam is emitted.

Since the needle emitter 18 or 21 does not react with At and moreover, A is stored in the metal reservoir 22, A
A stable At ion beam can be obtained for a long time until t disappears.

In FIG. 4(d), 26 is an At metal reservoir, and 27 is a conductive column 2.
B is a resistance heating plate, 29 is an emitter support part, and the needle-like emitter 18 or 21 supported by the emitter support part 29 is A4.
It penetrates the metal reservoir 26 and the resistance heating plate 28 and projects outward. At this time, a slight gap is left between each penetrating portion so that molten At can be supplied to the tip of the needle emitter 18 or 21. As the resistance heating plate 28, a composite boride made of carbon BNKTiB2 which does not react with At can be used. With this configuration, if At is placed in the metal reservoir 26 and a current is passed through the conductive column 27, the resistance heating plate 28 will be heated, and the needle emitter 18 or 21 and the metal reservoir 26 will be heated. The heated At in the metal reservoir 26 is melted and supplied to the tip of the needle emitter 18 or 21. Therefore, Fig. 4 (cl
In the same way as in case 2, an M ion beam that is stable for a long time can be obtained.

FIG. 5 shows the ion beam emission characteristics of the At ion gun of the present invention. The At ion gun uses FIG.
After cutting out, a needle-shaped emitter 21 having a tip curvature of ~5 μm was produced by boring. This needle-shaped emitter 21 was inserted into a carbon resistance heating plate 28 to construct an At ion gun. The emitted ion current was measured at a location 16 mm away from the ion gun using a Faraday cannob with an aperture of 5 mmφ.

As shown in FIG. 5, the ion beam started to be emitted at around 87 kV, a large angular current density was obtained, and the device operated stably for a long time. No reaction between the emitter and A/ was observed, and the characteristics did not change during operation. In addition,
The threshold voltage for ion emission is lowered by reducing the curvature of the emitter tip.

As explained above, the acicular emitter of the 5-field emission type liquid metal ion gun uses a material that does not easily react with molten M, so it has the advantage of being able to obtain a high-intensity M ion beam that is stable for a long time. There is. Furthermore, this M ion beam is a Ga ion beam obtained using a conventional field emission type liquid metal ion gun.

Since it has a smaller mass number than In, Au, etc., it has a narrow energy width and a large angular current density. That is, the beam diameter of the focused ion beam can be reduced and the current density can be increased with the same electron optical system performance. Therefore, since At has good compatibility with LSI processes, it can be applied to various patterning (exposure, etc.), ion implantation, microetching, microadhesion, and ion beam microanalysis IJ system.

Although the field emission type liquid metal ion gun of the present invention was developed to obtain an M ion beam, it can also be used when generating an ion beam of metals other than M (for example, Ga, In, 8n, Au, etc.). Needless to say, it is also used.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional field emission type liquid metal ion gun.
Figures 2 (al to (b)), Figures 3 (a) to (c), and Figures 4 (al to (d)) are the field emission type liquid metal A and aAt ion gun configuration diagrams of the present invention and their respective configuration diagrams. Fig. 5 is an explanatory diagram of the method for manufacturing a needle-shaped emitter, and is a diagram showing the ion beam emission characteristics of the A/= ion gun of the present invention. 1... needle-shaped metal emitter 2... extraction electrode 3... Power supply -4...
Heating support °5...Metal for ion extraction 6...
Heating power source 7... Insulating holder 8... Conductive support part 9... Heating support part 10... Acicular metal emitter part 11... Heating converted into boride or carbide Support part 12...acicular emitter part 13 converted into boride or carbide...base material 14...acicular emitter matrix 15...acicular emitter part 16 with integrated heating part・・・
・Connection part 17...High melting point metal thin wire 18...
・Acicular emitter of converted boride or carbide 19...Base material 20...Rod 21...
・Needle-torture emitter 22...kA Metal reservoir 26...
・Support part 24 of needle-shaped transmitter 24... Heating resistance wire 25... Insulating heat conductor 26... At metal reservoir 27... Conductive column 2
8... Resistance heating plate 29... Emitter support portion Patent applicant Junnosuke Nakamura, patent attorney representing Nippon Telegraph and Telephone Public Corporation

Claims (1)

[Scope of Claims] (1) A field emission type liquid metal ion gun, characterized in that the needle-like emitter is composed of a conductive boride, a conductive composite boride, or a conductive carbide. Ejection type liquid metal aluminum ion gun. (2) Ti boride as the conductive boride; a composite boride containing Ti boride in BN as the conductive composite boride;
The field emission type liquid metal aluminum ion gun according to claim 1, characterized in that a carbide of Ti is used as the conductive carbide. (6) The needle-shaped emitter of the field emission type liquid metal ion gun,
A method for manufacturing a field emission type liquid metal aluminum ion gun, characterized in that it is manufactured by converting a high melting point metal bus bar into a boride or carbide by solid-gas or solid-liquid reaction. (4) The needle-shaped emitter of the field emission type liquid metal ion gun,
A process of cutting out an emitter matrix from an emitter base material made of conductive boride, conductive composite boride, or conductive carbide by electrical discharge machining, machining, or ultrasonic machining, and chemically processing the cut-out matrix. 1. A method for manufacturing a field emission type liquid metal aluminum ion gun, comprising the step of making the tip sharp by polishing or electrolytic polishing.