Focusing electrode for cathode arrangement, electron gun, and lithography system comprising such electron gun

Patent metadata

Field	Value
Publication number	US-10622188-B2
Application number	US-201615203888-A
Country	US
Kind code	B2
Filing date	Jul 7, 2016
Priority date	Dec 30, 2013
Publication date	Apr 14, 2020
Grant date	Apr 14, 2020

Abstract

The invention relates to a cathode arrangement comprising:
a thermionic cathode comprising an emission portion provided with an emission surface for emitting electrons, and a reservoir for holding a material, wherein the material, when heated, releases work function lowering particles that diffuse towards the emission portion and emanate at the emission surface at a first evaporation rate; a focusing electrode comprising a focusing surface for focusing the electrons emitted from the emission surface of the cathode; and an adjustable heat source configured for keeping the focusing surface at a temperature at which accumulation of work function lowering particles on the focusing surface is prevented.

First claim

The invention claimed is:

1. A cathode arrangement comprising a
focusing electrode, wherein the focusing electrode comprises:
a cylindrical shell defining a cavity for accommodating a cathode body,
a front cover provided with a circular electron transmission aperture and a focusing surface, wherein the front cover further comprises an inner electrode surface arranged for supporting the cathode body, and
a support structure comprising a confining arrangement,
wherein the cylindrical shell is mounted in or to the support structure, and wherein the cylindrical shell is provided with slits or cut-outs forming angular interspacings accommodating the confining arrangement, the confining arrangement comprising:
a main body located outside of the cylindrical shell, and
one or more features radially inwardly protruding from the main body through said slits or cut-outs into said cylindrical shell, whereby the one or more features of the confining arrangement:
i) confines movement of the cathode body with respect to the focusing electrode and/or with respect to the support structure, and
ii) confines movement of the focusing electrode with respect to the support structure, while allowing for thermal expansion of said cathode body and said focusing electrode.

2. The cathode arrangement according to claim 1 , wherein the focusing surface is oriented at an angle to the inner electrode surface of the front cover, whereby the focusing surface and the inner electrode surface converge at the transmission aperture.

3. The cathode arrangement according to claim 1 , provided with three spacing structures on the inner electrode surface for providing a spacing between the focusing electrode and an emission portion of the cathode body.

4. The cathode arrangement according to claim 1 , wherein the inner electrode surface is arranged to support the cathode body such that the cathode body is resting on the inner electrode surface by means of gravity.

5. The cathode arrangement according to claim 1 , wherein radial spacers are provided for providing a radial interspacing between the inner surface of the cylindrical shell and the cathode body.

6. The cathode arrangement according to claim 1 , wherein a heat trapping surface is provided on an inner surface of the cylindrical shell, the heat trapping surface being arranged for receiving heat radiation emitted by the cathode body during use and/or wherein the inner electrode surface is provided with a heat trapping surface.

7. The cathode arrangement according to claim 1 , arranged for moveably accommodating the cathode body.

8. The cathode arrangement according to claim 1 , wherein the cylindrical shell is provided with support elements extending from the cylindrical shell for supporting the focusing electrode on the support structure.

9. The cathode arrangement according to claim 1 wherein the support structure comprises or forms part of a support electrode.

10. A cathode arrangement comprising:
a focusing electrode comprising:
a cylindrical shell defining a cavity for accommodating a cathode body, and
a front cover provided with a circular electron transmission aperture and a focusing surface, wherein the front cover further comprises an inner electrode surface, arranged for supporting the cathode body, and
a support structure provided with a confining arrangement for confining the focusing electrode and/or the cathode body with respect to the support structure, wherein the cylindrical shell comprises angular interspacings formed as slits or cut-outs in the cylindrical shell for accommodating the confining arrangement, and
wherein the confining arrangement comprises one or more end stops, the end stops having surface areas facing, but arranged at a distance from, one or more surface areas of the cathode body and/or focusing electrode, such that physical contact between the confining arrangement and the cathode arrangement is avoided.

11. The cathode arrangement according to claim 10 , wherein the cylindrical shell is provided with support elements extending from the cylindrical shell, and configured such that the focusing electrode rests, by means of gravity, on the support structure via three substantially point contacts formed between three support elements and the support structure.

12. The cathode arrangement according to claim 11 , further comprising:
a thermionic cathode having an emission portion provided with an emission surface for emitting electrons and a reservoir for holding a material, which, when heated, releases work function lowering particles that diffuse towards the emission portion and emanate at the emission surface at a first evaporation rate; wherein the thermionic cathode is arranged within said cylindrical shell of the focusing electrode, and
an adjustable heat source configured for keeping the focusing surface of the focusing electrode at a temperature at which accumulation of work function lowering particles on the focusing surface is prevented, or at least minimized.

13. The cathode arrangement according to claim 12 , wherein the thermionic cathode further comprises a cathode body housing the emission portion and the reservoir, wherein the heat trapping surface is in thermal communication with the focusing surface, and wherein the focusing electrode is heated mainly by thermal radiation emitted by the cathode body.

14. The cathode arrangement according to claim 12 , wherein the adjustable heat source is configured for heating the cathode body.

15. The cathode arrangement according to claim 12 , wherein the focusing electrode comprises a transmission aperture having a transmission perimeter defining an area which is smaller than the emission surface area.

16. The cathode arrangement according to claim 12 , wherein the thermionic cathode and the focusing electrode are arranged such that thermal conduction from the cathode to the focusing electrode is avoided or at least minimized.

17. The cathode arrangement according to claim 12 , wherein the emission portion is provided with a non-emission surface surrounding the emission surface, wherein the focusing electrode comprises an inner electrode surface facing the emission portion, and wherein at least one of the inner electrode surface and the non-emission surface is provided with three spacing structures for providing a spacing between the focusing electrode and the emission portion.

18. An electron gun for generating an electron beam, the electron gun comprising:
a cathode arrangement according to claim 1 or claim 10 comprising a thermionic cathode having an emission portion provided with an emission surface for emitting electrons for generating a plurality of electrons; and
at least one shaping electrode for shaping the generated electrons into the electron beam.

19. An electron beam lithography system for exposing a target using at least one electron beamlet, the system comprising:
a beamlet generator for generating the at least one electron beamlet;
a beamlet modulator for patterning the at least one electron beamlet to form at least one modulated beamlet;
a beamlet projector for projecting the at least one modulated beamlet onto a surface of the target;
wherein the beamlet generator comprises an electron gun according to claim 18 .

20. The cathode arrangement according to claim 10 , wherein a heat trapping surface is provided on an inner surface of the cylindrical shell, the heat trapping surface being arranged for receiving heat radiation emitted by the cathode body during use.

Assignees

• Asml Netherlands Bv

Inventors

• Dinu-Gürtler Laura
• Hogervorst Eric Petrus

Classifications

• H01J1/15 Primary

  Cathodes heated directly by an electric current · CPC title

• H01J37/075

  Electron guns using thermionic emission from cathodes heated by particle bombardment or by irradiation, e.g. by laser · CPC title

• H01J2229/481

  Focusing electrodes · CPC title

• H01J3/027

  Construction of the gun or parts thereof (H01J3/021 - H01J3/025, H01J3/026 and H01J3/028 take precedence) · CPC title

• H01J37/3174 Primary

  Particle-beam lithography, e.g. electron beam lithography · CPC title