# US 2014/0197336 A1 · Electron gun and charged particle beam device

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- Number: US 2014/0197336 A1
- Document ID: US20140197336A1
- Status: Published application
- Kind: A1
- Application number: 14/240,333
- Filed: 2012-05-22
- Published: 2014-07-17
- Earliest claimed: 2011-08-22
- Assignees: Hitachi High-Technologies Corporation
- Inventors: Shun-ichi Watanabe; Takashi Onishi; Yoichi Ose; Kuniyasu Nakamura; Masaru Moriyama; Tomonori Suzuki
- Web page: https://patentgrep.com/patent/US20140197336A1

## CPC

- H01J 37/065: Construction of guns or parts thereof (H01J37/067 - H01J37/077 take precedence)
- H01J 2237/0206: Extinguishing, preventing or controlling unwanted discharges
- H01J 2237/0213: Avoiding deleterious effects due to interactions between particles and tube elements
- H01J 2237/026: Shields
- H01J 2237/045: Diaphragms
- H01J 2237/06316: Schottky emission
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## Abstract

The objective of the present application is to suppress the occurrence of flares and to reduce the amount of secondary electrons arising at an aperture provided to the lead-out electrode of an electron gun. By coating a thin film having a low rate of secondary electron emission such as carbon onto the aperture of a lead-out electrode closest to an electron source in an electron gun, it is possible to reduce the amount of secondary electrons arising. Secondary electrons arising at the lead-out electrode, are reduced, and so as a result, flare is reduced. By incorporating two apertures to the lead-out electrode, and applying to the two apertures a potential that is equipotential to the lead-out electrode, it is possible to eliminate an electric field from seeping from under to over the lead-out electrode. Secondary electrons arising when an electron beam impacts the lead-out electrode cease to incur force in the direction of passage from the lead-out electrode, and consequently there is a reduction in flares.

## Claims

### Claim 1

An electron gun comprising:
an electron source;
an extracting electrode configured to apply an electric field to the electron source for extracting electrons from the electron source, the extracting electrode including an aperture configured to pass a part of electrons from the electron source; and
an accelerating electrode configured to accelerate electrons extracted using the extracting electrode at a predetermined accelerating voltage, wherein:
one or more of the apertures are provided; and
a surface of a base material of at least an aperture closest to the electron source is coated with a material having a secondary electron emission rate of 0.6 or less when irradiation energy of primary electrons colliding against the aperture ranges from 2 to 3 kV.

### Claim 2 (depends on 1)

The electron gun according to claim 1, wherein the coating material applied to the surface of the base material of the aperture is carbon or boron.

### Claim 3 (depends on 1)

The electron gun according to claim 1, wherein the electron gun is a Schottky electron gun or a field emission electron gun.

### Claim 4 (depends on 1)

The electron gun according to claim 1,
wherein the extracting electrode is provided with two upper and lower apertures; and
a potential of these apertures is made equal to a potential of the extracting electrode.

### Claim 5 (depends on 4)

The electron gun according to claim 4, wherein in the apertures provided on the extracting electrode, an inner diameter of the lower aperture is greater than an inner diameter of the upper aperture.

### Claim 6 (depends on 5)

The electron gun according to claim 5,
wherein the electron gun is a Schottky electron gun, and
a distance between the two apertures provided on the extracting electrode is one time the inner diameter of the lower aperture or more.

### Claim 7 (depends on 5)

The electron gun according to claim 5,
wherein the electron gun is a field emission electron gun, and
a distance between the two apertures provided on the extracting electrode is twice the inner diameter of the lower aperture or more.

### Claim 8 (depends on 1)

A charged particle beam device comprising:
a main body including the electron gun according to claim 1;
a power supply configured to supply a voltage or an electric current for driving the main body, and
a controller configured to control the main body by controlling an output of the power supply.