JP2004006368A - Diffusion replenishment electron source, its manufacturing method, and electron application device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a diffusion replenishment type electron source that is used for an electron beam application device such as an electron microscope or electron beam lithography device or the like, that has a high electron flow density and is actuated stably over a long period, and is highly resistant against any mechanical shock during the fabrication process and also has a high yield rate completing fabrication process in a short time. <P>SOLUTION: A needle-like single crystal wire 1 of a refractory metal such as W, Mo or Re is joined to the tip of a hairpin-shaped filament 2 of a refractory metal such as Mo or Re. Powders of metals such as Ti, Zr, Hf, Y, Th, Sc, Be, which have a lower work function and lower electric negativity than that of the single crystal wire 1, or compound powders of these are made into a slurry by means of an organic solvent in which butyl acetate or isoamyl acetate is added into cellulose nitrate are applied near the joint between the single crystal wire 1 and the filament 2, and they are sintered by heating in a vacuum to prepare the source of replenishment 3. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to an electron source used for an electron beam application device such as an electron microscope or an electron beam lithography device, and in particular, a high-brightness, long-life, high-stable, and diffusion-supply-type electron source with a good production yield, The present invention relates to a manufacturing method and an electronic application device.
[0002]
[Prior art]
Conventionally, a lanthanum hexaboride thermionic electron source or a W <310> field emission electron source has been used as an electron source for an electron beam application apparatus such as an electron beam lithography apparatus and a scanning electron microscope. However, in recent years, instead of these, a so-called diffusion-supply type electron, which has higher luminance than a lanthanum hexaboride thermionic source, is easier to handle than a W <310> field emission electron source, and provides stable electron emission. Sources are being used. That is, a replenishing source made of a metal such as zirconium or titanium and oxygen is provided in the electron source itself, and replenished from the replenishing source to the tip of the needle-like tungsten W <100> single crystal by thermal diffusion to form an adsorption layer. The work function at the tip of the single crystal is reduced (JP-A-59-49065, U.S. Pat. No. 3,814,975). Thereby, high-luminance and stable electron emission can be obtained. When using this electron source, an electric field is applied while the tip of the W <100> single crystal is heated to 1000 to 2000K. Then, thermally excited electrons having higher energy than a potential barrier generated by the mirror potential of the electrons and the electric field, and electrons transmitted through the potential barrier are emitted. By the way, as a method of forming a supply source of metal or oxygen to be adsorbed on the surface of the tip of the single crystal, a hydrogen compound powder is applied in a slurry state with isoamyl acetate, and then heated at a high temperature in an oxygen atmosphere and fired. There is a method of sintering and hardening (U.S. Pat. No. 3,814,975, JP-A-6-76731) and a method of sintering by heating the oxide powder at a high temperature in vacuum after coating (JP-A-59-49065).
[0003]
[Problems to be solved by the invention]
However, in such a diffusion supply type electron source, in order to manufacture a supply source of metal or oxygen to be adsorbed on the surface of the tip of the needle-like single crystal for emitting electrons, application of a supply source powder and vacuum Sintering by high-temperature heating is required. In the above-described method for producing a replenishing source, isoamyl acetate is generally used as a solvent for applying the powder, and other than that, water or an organic solvent such as thinner is used. However, with these solvents, there is a problem that the applied replenishment source is usually brittle when dried, and peels off before sintering at high temperature. In addition, some organic solvents do not completely evaporate even after heating at a high temperature, and disperse at the tip of the single crystal, thereby inhibiting the emission of electrons.
[0004]
The present invention has been made in order to solve such a problem, and after applying a replenishment source powder, the powder does not peel off even when the organic solvent is dried, and is short-circuited by heating at a high temperature. An object of the present invention is to provide a diffusion-supplying electron source which does not hinder electron emission by evaporating an organic solvent in a time, a method of manufacturing the electron source, and an electronic application device.
[0005]
[Means for Solving the Problems]
In order to achieve this object, in the present invention, a single-crystal wire made of a high-melting-point metal is joined to the tip of a filament made of a high-melting-point metal, and a joint between the filament and the single-crystal wire, or at least one of them. The replenishing source powder is applied in a slurry state with an organic solvent containing nitrocellulose, and then heated in a vacuum to sinter the powder to obtain a replenishing source. At this time, any material of W, Mo or Re is used as the filament and the single crystal wire, and at least one of Ti, Zr, Hf, Y, Th, Sc, Be, and La is used as the replenishing source powder. One kind of metal powder or its compound powder is used. As a typical example, a W single crystal line having a <100> crystal orientation is used as a single crystal line, and an oxide of Zr is used as a supply source powder to be applied.
[0006]
[Action]
In this method of manufacturing a diffusion-supplying electron source, when manufacturing a supply source for diffusing and supplying metal atoms having a low work function to the tip of a needle-like single crystal, a metal powder forming the supply source, or The replenishing source powder such as oxides is applied in a slurry form with an organic solvent containing nitrocellulose, so even after the organic solvent is dried, the replenishing source metal powder and its compound powder can be strongly used by the nitrocellulose. Is held. Therefore, the applied powder does not peel off due to mechanical impact. In addition, nitrocellulose is a type of explosive and vaporizes explosively at high temperatures. Therefore, the carbon, hydrogen, nitrogen, etc. of the nitrocellulose contained in the organic solvent are vaporized at that time due to high temperature heating when sintering the replenishment source powder, so that after the powder sintering, those impurities are completely removed. You. Therefore, carbon, hydrogen, nitrogen, and the like contained in the organic solvent are not diffused and adsorbed at the tip of the single crystal of the electron source, thereby preventing the emission of electrons.
[0007]
【Example】
The structure of a diffusion-supplying electron source according to the present invention and a method of manufacturing the same will be described below based on examples. However, in this embodiment, tungsten is used as a material of the electron source, and zirconium and oxygen are used as materials of the replenishment source. FIG. 1 shows a configuration diagram of a diffusion supply type electron source according to the present invention.
[0008]
First, a polycrystalline tungsten wire having a diameter of 0.15 mm is molded into a hairpin type to form a filament 2. A tungsten single crystal wire having an axial orientation of <100> is joined to the apex of the center tip of the filament 2, and the tip is a NaOH aqueous solution. The single crystal chip 1 is formed by electrolytic polishing in the inside. Next, a slurry of zirconium oxide powder having a low work function in the form of a slurry with a solvent obtained by mixing about 10% of nitrocellulose in isoamyl acetate is used as the tip of the filament 2, the middle of the single crystal chip 1, or the single crystal. It was applied to the base of the chip 1 to form a supply source 3. Here, 4 is a terminal made of stainless steel or the like to which the filament 2 is spot-welded, and 5 is a ceramic insulator.
[0009]
Next, a zirconium oxide powder as a replenishment source powder was applied by the above-described method, air-dried for several hours in the air, and then placed in a high vacuum container as shown in FIG. FIG. 2 shows an apparatus configuration for manufacturing and evaluating an electron source. The electron source including the single crystal chip 1, the filament 2, the replenishing source 3, and the like is attached to the extraction electrode 10 in a state where the suppressor electrode 20 is covered so that only the tip of the single crystal chip 1 protrudes. I have. The suppressor electrode 20 is an electrode for suppressing unnecessary thermoelectrons emitted from portions other than the tip of the single crystal. A negative potential is applied to the single crystal chip 1 and the filament 2 by the power supply 8 for the suppressor. Have been. A higher potential than the single crystal chip 1 is applied to the extraction electrode 10 by the extraction power supply 7 of a high voltage. An ammeter 9 for measuring the total current of electrons emitted from the single crystal chip 1 is connected in series to an extraction power source 7, and the filament 2 can be energized and heated by a heating power source 6. The electron beam 21 extracted by the extraction electrode 10 is applied to the phosphor plate 11 coated with a phosphor. The fluorescent plate 11 has a small hole in the center, and a Faraday cup 12 for measuring the current intensity of the electron beam is mounted below the small hole. The electron beam 21 that has passed through the small hole at the center of the fluorescent plate 11 enters the Faraday cup 12 and is measured by the ammeter 13. Next, the startup of the electron source and the procedure of the evaluation experiment will be described.
[0010]
First, the filament 2 is energized and heated by the heating power source 6 to sinter the supply source 3. At this time, the temperature is first raised to about 1000 K in 5 minutes or more, and then the heating current is slowly increased to about 1800 K in 30 minutes or more. Thereby, the sintering of the supply source 3 is almost completed. Thereafter, a high voltage is gradually applied between the extraction electrode 10 and the extraction power source 7 and the voltage is fixed at about 2 kV. Then, metal atoms are diffused from the replenishment source to the tip of the needle-like single crystal, and an adsorption surface having a low work function is formed on the (100) crystal face at the tip. Thus, electron emission starts, and the total current of the emitted electrons measured by the ammeter 9 gradually increases. Then, a circular electron emission pattern appears on the fluorescent screen 11 within about one hour. This circular emission pattern is shown in FIG. The electron flow density of the emitted electron beam was in the range of 0.05 to 1 mA / sr, depending on the radius of curvature of the tip of the single crystal chip.
[0011]
Although several tens of electron sources were manufactured by the above operation, a normal circular electron emission pattern was obtained within one hour after sintering of the replenishment source 3, and thereafter, the emitted electron current was stable. . For comparison, when the zirconium oxide powder was applied using various other solvents, the replenishing source 3 was peeled off while being set in the vacuum container, and an electron was not released. Problems such as 48 hours or more are required until electron emission starts later.
[0012]
FIG. 4 is a table summarizing the above results. The strength of the evaluation items shown in FIG. 4 was evaluated by the following test. That is, an electron source coated with a zirconium oxide replenishing source, left to stand in the air for several hours, and dried is placed in a metal case, fixed, dropped on a concrete floor from a height of 5 cm, and the replenishing source is peeled off. Experimented to see if there is any. In addition, as a criterion for determining that normal electron emission was obtained, a circular electron emission pattern as shown in FIG. 3 was obtained. According to the above results, the replenishment source did not peel off in the drop test when it was coated with nitrocellulose + isoamyl acetate and nitrocellulose + butyl acetate (these are generally called collodion solution), and when methyl methacrylate + acetone It was found that this was the case with the application. On the other hand, it was found that the time required for normal electron emission after sintering was the shortest in the case of the collodion solution, and it took 48 hours or more in the case of methyl methacrylate + acetone.
[0013]
As described above, when zirconium oxide powder is applied with a so-called collodion solution containing nitrocellulose in an organic solvent, the strength before sintering is dramatically improved, and after sintering, the electron beam is irradiated. It was found that the time required for the release to begin was short.
[0014]
In the above embodiment, an electron source using zirconium oxide as a replenishing source has been described. However, the present invention is not limited to this, and an electron source coated with a compound powder of Ti, Zr, Hf, Y, Th, Sc, Be, and La may be used. The same strength effect as in the case of zirconium oxide was obtained, and electron emission was also confirmed.
[0015]
【The invention's effect】
As described above, in the diffusion supply type electron source according to the present invention, the method of manufacturing the same, and the electronic application apparatus, the supply source powder is applied in a slurry state with an organic solvent containing nitrocellulose, and is applied during the manufacturing process. A diffusion-supply type electron source that is resistant to mechanical shock, completes the manufacturing process in a short time, and has a good yield and stable electron emission is realized.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a diffusion supply type electron source according to the present invention.
FIG. 2 is a configuration diagram of an apparatus for manufacturing and evaluating characteristics of an electron source according to the present invention.
FIG. 3 is a light emission pattern of a fluorescent plate when normal electron emission is obtained from an electron source.
FIG. 4 is a table comparing the strength of a replenishment source manufactured using various solvents and the time required for electron emission.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Single crystal chip 2 ... Filament 3 ... Supply source 4 ... Terminal 5 ... Ceramic insulator 6 ... Heating power supply 7 ... Extraction power supply 8 ... Suppressor power supply 9 ... Ammeter 10 ... Extraction electrode 11 ... Fluorescent plate 12 ... Faraday cup 13 ... Electric current Total 20: suppressor electrode 21: electron beam

Claims (9)

A filament made of a high melting point metal, a single crystal line made of a high melting point metal joined to the tip of the filament, and a replenishment source formed at a joint or at least one of the filament and the single crystal line. Have
The replenishment source is formed by applying a replenishment source material in the form of a slurry with an organic solvent obtained by adding butyl acetate or isoamyl acetate to nitrocellulose, and then applying the slurry in a vacuum to form a replenishment source. Type electron source. The diffusion-supplying electron source according to claim 1,
A diffusion-supplying electron source, wherein a metal containing any of W, Mo, and Re is used as the filament and the single crystal wire. The diffusion-supplying electron source according to claim 1,
A diffusion supply electron source, wherein the supply source material is an oxide of at least one metal selected from the group including Ti, Zr, Hf, Y, Th, Sc, Be, and La. The diffusion supply electron source according to any one of claims 1 to 3,
The single crystal line contains a single crystal having a W <100> orientation. An electronic application device using the diffusion supply type electron source according to any one of claims 1 to 4. A single crystal wire made of high melting point metal is joined to the tip of a filament made of high melting point metal,
A supply source material is applied in a slurry form with an organic solvent obtained by adding butyl acetate or isoamyl acetate to nitrocellulose, at a joint or at least one of the filament and the single crystal wire,
A method for manufacturing an electron source, comprising forming a replenishing source by sintering the slurry by heating the joint in a vacuum. The method for manufacturing an electron source according to claim 6,
A method for manufacturing an electron source, characterized in that an oxide of at least one metal selected from the group including Ti, Zr, Hf, Y, Th, Sc, Be, and La is used as the supply source material. The method for manufacturing an electron source according to claim 6,
A method of manufacturing an electron source, wherein a metal containing any of W, Mo, and Re is used as the filament and the single crystal wire. The method for manufacturing an electron source according to claim 6,
A method of manufacturing an electron source, wherein a single crystal having a W <100> orientation is used as the single crystal line.

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