JP4040531B2 - Diffusion-supplemented electron source and electronic application device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an electron source used in an electron beam application apparatus such as an electron microscope or an electron beam drawing apparatus, and in particular, a diffusion supply electron source and an electron having high brightness, long life, high stability, and good production yield. It relates to applied devices .
[0002]
[Prior art]
Conventionally, a lanthanum hexaboride thermoelectron source or a W <310> field emission electron source has been used as an electron source of an electron beam application apparatus such as an electron beam drawing apparatus or a scanning electron microscope. However, in recent years, instead of these, electrons called so-called diffusion replenishment type, which has higher brightness than lanthanum hexaboride thermionic sources, is easier to handle than W <310> field emission electron sources, and can obtain stable electron emission. Sources have been used. This is because a replenishment source made of a metal such as zirconium or titanium and oxygen is provided in the electron source itself, and the needle-like tungsten W <100> single crystal tip is replenished by thermal diffusion from the replenishment source to form an adsorption layer. The work function at the tip of the single crystal is reduced (Japanese Patent Laid-Open No. 59-49065, US Pat. No. 3,814,975). As a result, high-luminance and stable electron emission can be obtained. When this electron source is used, an electric field is applied with the W <100> single crystal tip heated to 1000-2000K. Then, thermally excited electrons having higher energy than the potential barrier generated by the mirror image potential of the electrons and the electric field, and electrons passing through the potential barrier are emitted. By the way, as a method for forming a replenishment source of metal or oxygen to be adsorbed on the surface of the single crystal, a hydrogen compound powder is applied in a slurry form with isoamyl acetate, and then heated at a high temperature in an oxygen atmosphere to be baked. There are a method of consolidating and hardening (US Pat. No. 3,814,975, JP-A-6-76731), a method of heating an oxide powder at a high temperature in a vacuum after coating (JP-A-59-49065), and the like.
[0003]
[Problems to be solved by the invention]
However, in such a diffusion replenishment type electron source, for the production of a replenishment source such as metal or oxygen adsorbed on the surface of the needle-like single crystal that emits electrons, application of replenishment source powder and in vacuum Sintering by high temperature heating is necessary. In the above-described replenishment source manufacturing method, isoamyl acetate is generally used as a solvent for applying powder, and water or organic solvents such as thinner are used in other cases. However, these solvents usually have a problem that, when dried, the applied replenishment source becomes brittle and peels off before sintering by high temperature heating. In addition, some organic solvents do not completely evaporate even after high-temperature heating, and there is a problem that the emission of electrons is inhibited by diffusing to the tip of the single crystal.
[0004]
The present invention has been made to solve such a problem, and after application of the replenishment source powder, even if the organic solvent is dried, the powder does not peel off, and is heated by heating at a high temperature. An object of the present invention is to provide a diffusion replenishment type electron source and an electronic application device in which the organic solvent evaporates over time and does not hinder electron emission.
[0005]
[Means for Solving the Problems]
In order to achieve this object, in the present invention, a single crystal wire made of a refractory metal is joined to a tip portion of a filament made of a refractory metal, and at least one of the joined portion of the filament and the single crystal wire. The replenishment source powder is applied in the form of a slurry with an organic solvent containing nitrocellulose, and heated in vacuum to sinter the powder to obtain a replenishment source. At this time, as the filament and the single crystal line, any material of W, Mo or Re is used, and as the replenishment source powder, at least one of Ti, Zr, Hf, Y, Th, Sc, Be and La is used. One kind of metal powder or compound powder thereof 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 powder to be applied.
[0006]
[Action]
In this diffusion replenishment type electron source, when a replenishment source for replenishing replenishment of a metal atom having a low work function is produced at the tip of a needle-like single crystal, the metal powder that forms the replenishment source, or its oxide As a replenishment source powder is applied in a slurry form with an organic solvent containing nitrocellulose, the metal powder and its compound powder as a replenishment source are strongly retained by nitrocellulose even after the organic solvent is dried. The Therefore, the applied powder does not peel off due to mechanical impact. Furthermore, nitrocellulose is a type of explosive that vaporizes explosively at high temperatures. Therefore, carbon, hydrogen, nitrogen, etc. of nitrocellulose contained in the organic solvent are vaporized at that time by high-temperature heating when sintering the replenishment source powder, so those impurities are completely removed after powder sintering. The Therefore, carbon, hydrogen, nitrogen, etc. contained in the organic solvent are diffused and adsorbed on the tip of the single crystal of the electron source, and electron emission is not inhibited.
[0007]
【Example】
The structure of the diffusion supply type electron source according to the present invention and the manufacturing method thereof will be described below based on examples. However, in this embodiment, tungsten is used as the material constituting the electron source, and zirconium and oxygen are used as the replenishment source material. FIG. 1 shows a configuration diagram of a diffusion supply electron source according to the present invention.
[0008]
First, a tungsten polycrystal wire having a diameter of 0.15 mm is formed into a hairpin shape to form a filament 2, a tungsten single crystal wire having an axial orientation <100> is joined to the apex of the central tip portion of the filament 2, and the tip is a NaOH aqueous solution. The single crystal chip 1 is produced by electrolytic polishing in the medium. Next, a slurry of zirconium oxide powder having a low work function mixed with isoamyl acetate in a solvent containing about 10% nitrocellulose is used as a slurry, and the tip of the filament 2, the intermediate portion of the single crystal chip 1, or the single crystal The replenishment source 3 was applied to the base of the chip 1. Here, 4 is a terminal such as stainless steel on which the filament 2 is spot welded, and 5 is a ceramic insulator.
[0009]
Next, zirconium oxide powder, which is a replenishment source powder, was applied by the above-described method, dried naturally in the atmosphere for several hours, 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 replenishment source 3, and the like is attached facing the extraction electrode 10 with the suppressor electrode 20 covered so that only the tip of the single crystal chip 1 protrudes. Yes. The suppressor electrode 20 is an electrode for suppressing unnecessary thermoelectrons emitted from portions other than the tip of the single crystal, and a negative potential is applied to the single crystal chip 1 and the filament 2 by the suppressor power supply 8. It has been. A higher potential than the single crystal chip 1 is applied to the extraction electrode 10 by a high voltage extraction power source 7. 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 supply 7, and the filament 2 can be energized and heated by a heating power supply 6. The electron beam 21 extracted by the extraction electrode 10 is applied to the fluorescent 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 attached 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 start-up of the electron source and the evaluation experiment procedure are shown.
[0010]
First, the filament 2 is energized and heated by the heating power source 6 to sinter the replenishment source 3. At this time, the temperature is first raised to about 1000K over 5 minutes, and then the heating current is slowly increased to about 1800K over 30 minutes. Thereby, sintering of the replenishment source 3 is almost completed. Thereafter, a high voltage is gradually applied to the extraction electrode 10 by the extraction power source 7 and fixed at a voltage of about 2 kV. Then, metal atoms diffuse from the replenishment source to the needle-like single crystal tip, and an adsorption surface with a low work function is formed on the (100) crystal face at the tip. As a result, 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 1 hour. This circular discharge pattern is shown in FIG. The electron flow density of the emitted electron beam has a value 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]
Dozens of electron sources were manufactured by the above operation, but in each case, a normal circular electron emission pattern was obtained within one hour after the replenishment source 3 was sintered, and then the emission electron flow was stable. . For comparison, when zirconium oxide powder was applied using other various solvents, the replenishment source 3 peeled off during setting in the vacuum vessel, and no electrons were emitted. There was a problem that it took more than 48 hours for the electron emission to start 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. In other words, an electron source coated with zirconium oxide replenishment source and left to dry in the atmosphere for several hours is put in a metal case and fixed, dropped from a height of 5 cm onto a concrete floor, and the replenishment source peels off. I experimented. Further, as a reference 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 does not peel off by the drop test when applied with nitrocellulose + isoamyl acetate and nitrocellulose + butyl acetate (the above is commonly referred to as collodion liquid), methyl methacrylate + acetone It was found that this was the case when the coating was applied. On the other hand, it was found that the time from the sintering until normal electron emission was obtained was the shortest in the case of the collodion liquid, and it took a very long time of 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. It has been found that the time until the release starts can be shortened.
[0014]
In the above embodiments, the electron source using zirconium oxide as the supply 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, La can also 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 replenishment type electron source and the electronic application apparatus according to the present invention, the replenishment source powder is applied in the form of a slurry with an organic solvent containing nitrocellulose, thereby applying mechanical shock during the manufacturing process. In addition, a diffusion replenishing type electron source capable of producing a stable electron emission with a high yield and a stable yield was realized.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a diffusion supply electron source according to the present invention.
FIG. 2 is a configuration diagram of an apparatus for manufacturing and characterization of an electron source according to the present invention.
FIG. 3 is a light emission pattern of a fluorescent screen 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 ... Phosphor plate 12 ... Faraday cup 13 ... Current Total 20 ... suppressor electrode 21 ... electron beam

Claims (6)

A filament made of a refractory metal, a single crystal chip made of a refractory metal formed with a tip that emits electrons bonded to the tip of the filament, a joint between the filament and the single crystal chip , A replenishment source formed at the tip of the filament or at the middle or root of the single crystal chip ,
The replenishment source was prepared by applying a replenishment source material slurried with an organic solvent obtained by adding butyl acetate or isoamyl acetate to nitrocellulose to the replenishment source forming portion of the filament to which the single crystal chip was bonded . after the diffusion supply type electron source, characterized in that it is formed by Rukoto sintered by heating in vacuum. The diffusion supply electron source according to claim 1,
A diffusion-supplemented electron source using a metal containing any one of W, Mo, or Re as the filament and the single crystal chip . The diffusion supply electron source according to claim 1,
The diffusion replenishment type electron source, wherein the replenishment source material is an oxide of at least one kind of metal selected from the group including Ti, Zr, Hf, Y, Th, Sc, Be, and La. The diffusion supply type electron source according to any one of claims 1 to 3,
The single crystal chip includes a single crystal having a W <100> orientation.   An electronic application apparatus using the diffusion supply type electron source according to any one of claims 1 to 4. A filament made of a metal containing W, Mo, or Re, and a single crystal chip made of a metal containing W, Mo, or Re, which is bonded to the tip of the filament and formed with a tip that emits electrons, Having a replenishment source formed at the junction between the filament and the single crystal chip, the tip of the filament or the middle or root of the single crystal chip,
  The replenishment source is made by applying a replenishment raw material containing an oxide of at least one metal of Ti, Zr, Hf, Y, Th, Sc, Be, and La in an organic solvent containing nitrocellulose. After being
  By flowing a heating current through the filament in a vacuum, the temperature is increased to about 1000K over 5 minutes, and then the heating current is gradually increased and heated to about 1800K over 30 minutes, A diffusion-supplemented electron source formed by sintering the slurry.

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