JPH10106464A - Electron source and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize application to a needle-like cathode by applying specific metallic oxide powder and an applying solvent to the needle-like cathode joined to a heating filament. SOLUTION: A heating filament 2 composed of a W-made wire rod molded in a hair pin shape is welded to a stainless steel terminal 4 embedded and installed in a ceramic insulating insulator 5, and a W single crystal wire rod 1 is welded to the center of its heating filament 2. Preferably, application, heating and sintering are performed on this needle-like cathode 1 by using an applying solvent composed of metallic oxide powder composed of a zirconium oxide, a titanium oxide, a scandium oxide or a hafnium oxide and a solvent containing an acetic ester. Preferably, when the zirconium oxide, the titanium oxide, the scandium oxide or the hafnium oxide are formed in a delivery quantity of 10×10<-6> g to 100×10<-6> g, application of zirconium or the like to the needle-like cathode can be uniformized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron source used for an electron beam irradiation apparatus such as an electron microscope and an electron beam drawing apparatus, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, as a new electron source, for example, zirconium (hereinafter referred to as Zr) has been formed on the surface of a single crystal needle-like material of a high temperature resistant metal material such as tungsten (hereinafter referred to as W) or molybdenum.
A surface diffusion type electron source in which titanium, hafnium, and the like and oxygen atoms (hereinafter, referred to as O) are adsorbed as a single atomic layer has been put to practical use. As a general configuration, a W single-crystal needle having a certain crystal orientation is joined to the apex of a hairpin-shaped W filament, and the tip of the single-crystal needle is sharpened by electric field polishing. Then, a hydride powder such as hydrogenated Zr is attached to the needle-shaped W single crystal having a sharpened tip, and heat treatment is performed in a vacuum atmosphere having an oxygen partial pressure to promote diffusion of Zr or the like. It forms an adsorbed layer of Zr and oxygen on a specific crystal face at the tip of a single crystal needle (for example, see US Pat.
No. 76731).

A case where such an electron source is used in a weak electric field intensity region where electric field discharge does not occur is particularly called Schottky emission.
r / O / W has been put to practical use (Journal of Vacuum Science Technology. B3 (1), 1
985, 220 (J. Va. Sci. Technol., B3 (1), 1)
985, p220)).

[0004]

JP-A-6-76731 discloses a method for manufacturing an electron source in which zirconium hydride is slurried with an organic solvent comprising isoamyl acetate, and the slurry is applied with a brush. Have been.

[0005] However, this slurry has a high evaporation rate, and it is difficult to apply the slurry uniformly on the needle cathode. As an adverse effect when it is not possible to apply uniformly around the needle cathode,
There is deformation of the acicular cathode during sintering of the acicular cathode. This is because the bias of the coating material on the needle-shaped cathode causes the needle-shaped electrode to bend in the direction of excessive application during sintering.

[0006] In addition, in the conventional brush application, it is difficult to keep the application amount constant, the life of the electron source varies, and the accuracy of the application position is low. There were problems such as getting up.

Further, in the conventional brush application, the coating material dries at the coating position and does not spread over the entire circumference of the needle cathode in one operation because of the rapid evaporation of the coating solvent. An operation has been performed in which a solvent is applied to one side and the other, which has not been completely applied by the application, is further applied. However, in this method, in a state where drying of the coated material previously applied has progressed to some extent,
Since the second application is performed, the two do not mix and have an uneven shape.

In view of the above-mentioned problems, the present invention provides a method of manufacturing an electron source that enables uniform application of zirconium or the like to a needle-shaped cathode by appropriate selection of a coating solvent, and enables uniform application. And to provide an electron source.

[0009]

A feature of the present invention is that a needle-shaped cathode bonded to a heating filament contains a metal oxide powder composed of zirconium oxide, titanium oxide, scandium oxide or hafnium oxide, and an acetate ester. An object of the present invention is to apply a coating solvent composed of a solvent and heat and sinter in a vacuum. According to this configuration, the use of a coating solvent containing an acetate ester can suppress rapid evaporation of the solvent, so that zirconium or the like can be uniformly coated on the needle-shaped cathode.

A further feature of the present invention is that a sphere is formed by a surface tension effect using a coating solvent containing zirconium oxide, titanium oxide, scandium oxide or hafnium oxide, and the needle-shaped cathode is rotated on the sphere. The object is to apply the solvent for application to the needle-shaped cathode by contact, and to heat and sinter in a vacuum. By employing such a manufacturing method, it is possible to form uniform zirconium or the like over the entire circumference of the acicular cathode. Further, by providing these manufacturing methods, it becomes possible to appropriately form a desired amount of Zr or the like.

Further, by providing these manufacturing methods, zirconium oxide, titanium oxide, scandium oxide or hafnium oxide is added to the needle-shaped electrode in an amount of more than 10 × 10 ⁻⁶ g and 100 × 10 ⁻⁶ g or less. It became possible to form.

The larger the amount of zirconium oxide or the like formed on the needle-shaped cathode, the longer the life of the electron source, and the easier it is to control the irradiation of electron beams when employed in an electron beam irradiation apparatus. Here, by providing the manufacturing method of the present invention, it becomes possible to form zirconium oxide or the like having a weight that cannot be realized by the conventional manufacturing method.

On the other hand, the upper limit of 100 × 10 ⁻⁶ g or less is a value based on the limit temperature (heat resistance limit) of the heating filament. That is, as the capacity of zirconium oxide or the like increases,
The heat capacity required for the sintering increases, and the sintering temperature increases accordingly. It is necessary to set the sintering temperature below the heat resistance limit of the heating filament.
^-6 g is a value satisfying such a condition.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing the structure of an electron source according to an embodiment of the present invention. FIG. 2 is a conceptual view showing a means for applying and coating a Zr oxide coating on the electron source shown in FIG. is there. In the electron source shown in FIG. 1, a heating filament 2 made of a W-shaped wire formed in a hairpin shape is welded to a stainless steel terminal 4 embedded and mounted in a ceramic insulator 5, and a long wire is provided at the center of the heating filament 2. A W single crystal wire having a thickness of 4 mm and a crystal axis orientation of (100) is welded. Then, the tip of the W single crystal wire is immersed in an aqueous solution of sodium hydroxide and worked by electropolishing so that the length a from the welding joint point to the tip is 1.3 mm, and the tip is conical-topped. Conical shape with an angle of 6 ° to 10 ° and a tip radius of curvature of 0.3μ
After obtaining the needle-shaped material 1 having a m-0.5 μm, the nitrogen content is 11.5% to 12.2% and the average molecular weight is 24,400 to 30,00.
2 to 4 mol% of a solution obtained by adding a solution obtained by moistening a polyhydric alcohol ester of nitric acid with isopropyl alcohol to 2-ethylbutyl acetate so that the weight content of the polyhydric alcohol ester of nitric acid becomes 10%. Zr oxide powder containing yttrium and stabilized as a cubic crystal and having a particle size of 1 μm or less was mixed at a weight mixing ratio of [solvent]: [Zr oxide
Powder] = 1.0: 1.2 and stirred to form a mixed solution.

The effects of including the polyhydric alcohol nitrate in the solution include binding the Zr oxide powder until sintering and improving the combustion efficiency. Further, nitric acid polyhydric alcohol ester has a function of self-combustion by heating in vacuum and does not remain as carbon, so that it is suitable as a combustion medium and a binding medium for Zr oxide.

Next, this mixed liquid is supplied to the discharge hole 11 shown in FIG. 2, and the discharge amount is set to 35 × 10 ⁻⁶ g by a supply pressure control means (not shown) and a supply time control means (not shown). Discharge from a discharge hole 11 equipped with three micrometers (not shown) and fixed to a holder (not shown) capable of finely moving the position three-dimensionally, and discharging by the surface tension of the mixed liquid A droplet 12 of the mixed liquid is formed in the hole 11, and one of the three axes of the three-dimensional movement is held and fixed so that the axis in the longitudinal direction of the needle-shaped object 1 is parallel. The needle-shaped object 1 is rotated about the axis in the length direction as a rotation center, the discharge hole 11 is moved in parallel with the rotation axis of the rotating needle-shaped object 1 and held at a desired position. The droplet 12 is brought into contact with the rotating needle 1 by moving the ejection hole 11 in the orthogonal direction, and the droplet 12 is moved to the needle 1 After applying the transfer to shape spheroidal, to move the discharge hole 11 away from the needles 1, and stops the rotation of the needles 1.

Next, the electron source precursor having the needle-shaped material 1 coated with the droplet 12 is mounted in a vacuum vessel having a power supply terminal for heating, and is rotated using a rotary pump and a diffusion pump / ion pump. While reducing the pressure in the vacuum vessel to 10 ^-6 Pa, the filament 2 was energized through the terminal 4 and heated for 15 minutes to a maximum temperature of 1773K.

By providing such a manufacturing method, it becomes possible to uniformly apply Zr oxide to the needle-shaped cathode.

[0020]

As described above in detail, according to the present invention, Z
An r / O supply source can be formed uniformly, and a supply source of a desired amount of Zr or the like can be appropriately formed.

Further, since the Zr / O supply source can be formed at a predetermined position and at a predetermined position, an electron source having a stable emission electron current, a long life and an excellent performance can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an electron source according to an embodiment of the present invention.

FIG. 2 is a conceptual view showing a means for applying a Zr oxide coating to the electron source of FIG. 1;

FIG. 3 is a cross-sectional view showing a configuration of a conventional electron source.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Needle of tungsten single crystal, 2 ... Heating filament, 3 ... Zr / O supply source, 4 ... Terminal, 5 ... Ceramic insulator, 6 ... Suppressor electrode, 7 ... Extraction electrode, 11
... ejection holes, 12 ... droplets.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01J 37/073 H01J 37/073 (72) Inventor Go Tsuyoshi Matsumoto 882-Chair, Oaza, Hitachinaka-shi, Ibaraki Prefecture Measuring Instruments Business, Hitachi, Ltd. Inside

Claims (8)

[Claims] 1. An electron source comprising a heating filament, a needle-like cathode joined to the heating filament, and an extraction electrode for extracting an electron beam from the needle-like electrode. A fixed substance made of zirconium, titanium oxide, scandium oxide or hafnium oxide is formed, and the weight of the fixed substance is more than 10 × 10 ⁻⁶ g and 100 × 10 ⁻⁶ g or less. Electron source. 2. An electron source according to claim 1, wherein said fixed substance is formed symmetrically with respect to said needle-shaped cathode. 3. A metal oxide powder made of zirconium oxide, titanium oxide, scandium oxide or hafnium oxide is provided on a needle-like cathode bonded to a heating filament.
Apply a coating solvent consisting of a solvent containing acetic ester,
A method for producing an electron source, comprising sintering in a vacuum. 4. The method according to claim 3, wherein the acetic acid ester is
A method for producing an electron source, which is any one of 2-ethylbutyl acetate, n-hexyl acetate, cyclohexyl acetate, ethylene glycol diacetate, n-butoxyethyl acetate, phenyl acetate, 2-ethylhexyl acetate, and benzyl acetate. 5. The method for producing an electron source according to claim 3, wherein the solvent contains a nitric acid ester of a polyhydric alcohol. 6. A sphere formed by a surface tension action using a coating solvent containing zirconium oxide, titanium oxide, scandium oxide or hafnium oxide, and the sphere is brought into contact with the needle-shaped cathode while rotating the needle-shaped cathode. Is applied to the needle-shaped cathode and heated and sintered in a vacuum. 7. The method according to claim 6, wherein the acetic acid ester contained in the coating solvent is 2-ethylbutyl acetate, n-hexyl acetate, cyclohexyl acetate, ethylene glycol diacetate, n-butoxyethyl acetate, phenyl acetate, acetic acid acetic acid. -A method for producing an electron source, wherein the electron source is any of ethylhexyl and benzyl acetate. 8. The method for manufacturing an electron source according to claim 6, wherein said coating solvent contains a nitric acid ester of a polyhydric alcohol.