Electron gun and electron beam application apparatus

Patent metadata

Field	Value
Publication number	US-12165828-B2
Application number	US-201917768244-A
Country	US
Kind code	B2
Filing date	Oct 31, 2019
Priority date	Oct 31, 2019
Publication date	Dec 10, 2024
Grant date	Dec 10, 2024

Abstract

An electron beam emitted from a photoexcited electron gun is increased in luminance. An electron gun 15 includes: a photocathode 1 including a substrate 11 and a photoelectric film 10 ; a light source 7 that emits pulsed excitation light; a condenser lens 2 that focuses the pulsed excitation light toward the photocathode; and an extractor electrode 3 that faces the photocathode and that accelerates an electron beam generated from the photoelectric film by focusing the pulsed excitation light by the condenser lens, transmitting the pulsed excitation light through the substrate of the photocathode, and causing the pulsed excitation light to be incident on the photocathode. The pulsed excitation light is condensed at different timings at different positions on the photoelectric film of the photocathode.

First claim

The invention claimed is:

1. An electron gun comprising:
a photocathode including a substrate and a photoelectric film;
a light source that emits a plurality of pulsed excitation lights;
a condenser lens that focuses each of the pulsed excitation lights toward the photocathode; and
an extractor electrode that faces the photocathode and that accelerates an electron beam generated from the photoelectric film by focusing each of the pulsed excitation lights by the condenser lens, transmitting each of the pulsed excitation lights through the substrate of the photocathode, and causing each of the pulsed excitation lights to be incident on the photocathode, wherein
each of the pulsed excitation lights is condensed at a different timing at a different position on the photoelectric film of the photocathode,
each of the plurality of pulsed excitation lights is condensed at one of a plurality of positions on the photoelectric film of the photocathode in a timing sequence according to a predetermined repeated cycle, and
a timing of each of the pulsed excitation lights condensed at the plurality of positions is controlled so as to not overlap with one another.

2. The electron gun according to claim 1 , wherein
the light source includes an angle modulation mechanism that changes an emission angle of the pulsed excitation lights.

3. The electron gun according to claim 2 , wherein
the angle modulation mechanism includes a pulse parallel light source and a spatial light modulator, and
each of the pulsed excitation lights from the pulse parallel light source is modulated by the spatial light modulator, and is emitted to the plurality of positions on the photoelectric film of the photocathode.

4. The electron gun according to claim 1 , further comprising:
a spherical aberration compensation plate disposed between the condenser lens and the photocathode, wherein
in an excitation light converging optical system including the light source, the spherical aberration compensation plate, and the condenser lens, a refractive index and a thickness of the spherical aberration compensation plate are determined such that each of the pulsed excitation lights condensed at each of the plurality of positions is narrowed down to a diffraction limit at a wavelength of the pulsed excitation light.

5. An electron gun comprising:
a photocathode including a substrate and a photoelectric film;
a light source that emits pulsed excitation light;
a condenser lens that focuses the pulsed excitation light toward the photocathode; and
an extractor electrode that faces the photocathode and that accelerates an electron beam generated from the photoelectric film by focusing the pulsed excitation light by the condenser lens, transmitting the pulsed excitation light through the substrate of the photocathode, and causing the pulsed excitation light to be incident on the photocathode, wherein
the pulsed excitation light is condensed at different timings at different positions on the photoelectric film of the photocathode,
the pulsed excitation light is condensed at a plurality of positions on the photoelectric film of the photocathode at a predetermined cycle, and timings of the pulsed excitation light condensed at the plurality of positions are different from each other,
the light source includes an angle modulation mechanism that changes an emission angle of the pulsed excitation light, and
the angle modulation mechanism includes a plurality of laser light sources, a plurality of optical fibers each having one of the plurality of laser light sources provided at a same end thereof, a collimator lens facing the other ends of the plurality of optical fibers, and a pulse power source that drives any one of the plurality of laser light sources.

6. The electron gun according to claim 5 , wherein
in an excitation light converging optical system including the light source and the condenser lens, the plurality of positions on the photoelectric film of the photocathode are set at a distance from a central axis of the excitation light converging optical system such that the pulsed excitation light condensed at each of the plurality of positions is narrowed down to a diffraction limit at a wavelength of the pulsed excitation light.

7. An electron beam application apparatus comprising:
a photoexcited electron gun including an excitation light converging optical system and a photocathode, the excitation light converging optical system including a light source and a condenser lens;
an electron optical system including a deflector that two-dimensionally scans a sample with a pulsed electron beam from the photoexcited electron gun; and
a control unit that controls the excitation light converging optical system to emit the pulsed electron beam from different positions on the photocathode at different timings, wherein
the control unit outputs a deflection control signal for controlling a trajectory of the pulsed electron beam in synchronization with a control signal for controlling emission of the pulsed electron beam such that the pulsed electron beam emitted from a different position on the photocathode is emitted to the same position on the sample.

8. The electron beam application apparatus according to claim 7 , wherein
the electron optical system includes an aligner that deflects the pulsed electron beam, and
the aligner deflects the pulsed electron beam according to the deflection control signal.

9. An electron beam application apparatus comprising:
a photoexcited electron gun including an excitation light converging optical system and a photocathode, the excitation light converging optical system including a light source and a condenser lens;
an electron optical system including a deflector that two-dimensionally scans a sample with a pulsed electron beam from the photoexcited electron gun;
a detector that detects electrons generated by the sample being irradiated with the pulsed electron beam and that outputs a detection signal; and
a control unit that controls the excitation light converging optical system to emit the pulsed electron beam from a plurality of positions on the photocathode at different timings, wherein
the control unit outputs a discrimination signal synchronized with a control signal for controlling emission of the pulsed electron beam, and is capable of discriminating, based on the discrimination signal, which position among the plurality of positions on the photocathode the pulsed electron beam is emitted to the sample from, in order to detect the detection signal output from the detector.

10. The electron beam application apparatus according to claim 9 , wherein
an image forming unit configured to form an image using a detection signal discriminated according to the discrimination signal as a detection signal at a different position on the sample.

11. The electron beam application apparatus according to claim 9 , wherein
the plurality of pulsed electron beams emitted from the plurality of positions of on the photocathode are swept in a first direction by the deflector to draw a trajectory extending in the first direction, and positions at which the plurality of pulsed electron beams are emitted to the sample are adjusted such that distances between the adjacent trajectories are equal to each other.

Assignees

• Hitachi High Tech Corp

Inventors

• Ohshima Takashi
• Morishita Hideo
• Ide Tatsuro
• KOHMU Naohiro
• Enyama Momoyo
• Ose Yoichi
• Agemura Toshihide
• Katane Junichi

Classifications

• H01J2237/06333

  Photo emission · CPC title

• H01J37/285

  Emission microscopes, e.g. field-emission microscopes · CPC title

• H01J37/265

  Controlling the tube; circuit arrangements adapted to a particular application not otherwise provided, e.g. bright-field-dark-field illumination · CPC title

• H01J37/22

  Optical {, image processing} or photographic arrangements associated with the tube · CPC title

• H01J37/1474

  Scanning means · CPC title