Apparatus and methods for aberration correction in electron beam based system

Patent metadata

Field	Value
Publication number	US-9607802-B2
Application number	US-201414567785-A
Country	US
Kind code	B2
Filing date	Dec 11, 2014
Priority date	Nov 2, 2011
Publication date	Mar 28, 2017
Grant date	Mar 28, 2017

Abstract

One embodiment relates to an apparatus for aberration correction in an electron beam lithography system. An inner electrode surrounds a pattern generating device, and there is at least one outer electrode around the inner electrode. Each of the inner and outer electrodes has a planar surface in a plane of the pattern generating device. Circuitry is configured to apply an inner voltage level to the inner electrode and at least one outer voltage level to the at least one outer electrode. The voltage levels may be set to correct a curvature of field in the electron beam lithography system. Another embodiment relates to an apparatus for aberration correction used in an electron based system, such as an electron beam inspection, or review, or metrology system. Other embodiments, aspects and features are also disclosed.

First claim

What is claimed is:

1. An apparatus for aberration correction in electron-optics of an electron beam system, the apparatus comprising:
an inner electrode surrounding an opening in the electron-optics, the inner electrode having a continuous annular planar surface extending unbroken from a circular inner perimeter to a circular outer perimeter in a plane of the opening;
at least one outer electrode around the inner electrode, the at least one outer electrode having a planar surface in the plane of the opening;
circuitry configured to apply an inner voltage level to the inner electrode and at least one outer voltage level to the at least one outer electrode; and
a blanker array within the opening which receives an incident electron beam and generates multiple beamlets of electrons,
wherein the inner voltage level and the at least one outer voltage levels, as applied to said electrodes, each causes an electric field that influences both electrons of the incident electron beam that are incident to the opening and the multiple beamlets of electrons outgoing from the opening.

2. The apparatus of claim 1 , wherein each of the inner voltage level and the at least one outer voltage level are controlled individually.

3. The apparatus of claim 2 , wherein the inner voltage level and the at least one outer voltage level are set to correct a curvature of field in the electron-optics.

4. The apparatus of claim 1 , wherein the inner electrode is centered on an optical axis of the electron-optics.

5. The apparatus of claim 1 , wherein the at least one outer electrode is a single outer electrode which is centered on an optical axis.

6. The apparatus of claim 1 , wherein the at least one outer electrode comprises a plurality of outer electrodes.

7. The apparatus of claim 1 , wherein the at least one outer electrode comprises four electrodes which are arranged in quadrants around the inner electrode.

8. The apparatus of claim 7 , wherein the inner voltage level and the at least one outer voltage level are set to correct a curvature of field and higher-order aberrations in the electron-optics.

9. The apparatus of claim 1 , wherein the planar surfaces of the inner electrode and the at least one outer electrode are in an image plane of the electron-optics.

10. The apparatus of claim 1 , wherein the planar surfaces of the inner electrode and the at least one outer electrode are in a pupil plane of the electron-optics.

11. A method of correcting aberration in electron-optics of an electron beam system, the method comprising:
adjusting an inner voltage level applied to an inner electrode surrounding an opening, the inner electrode having a continuous annular planar surface extending unbroken from an inner circumference to an outer circumference in a plane of the opening; and
adjusting at least one outer voltage level which is applied to at least one outer electrode around the inner electrode, the at least one outer electrode having a planar surface in the plane of the opening,
wherein the inner voltage level and the at least one outer voltage levels, as applied to said electrodes, each causes an electric field that influences both a beam of electrons incident to the opening and multiple beamlets of electrons outgoing from a blanker array in the opening.

12. The method of claim 11 , wherein the inner electrode has an annular planar surface with circular inner and outer perimeters.

13. The method of claim 11 , wherein the inner voltage level and the at least one outer voltage level are set to correct a curvature of field in the electron-optics.

14. The method of claim 11 , wherein the at least one outer electrodes comprises a plurality of outer electrodes arranged around the inner electrode.

15. The method of claim 14 , wherein the plurality of outer electrodes comprises four electrodes which are arranged in quadrants around the inner electrode.

16. The method of claim 15 , wherein inner voltage level and the at least one outer voltage level are set to correct a curvature of field and higher-order aberrations in the electron-optics.

17. An electron beam column comprising:
an electron source for generating an electron beam that travels along an optical axis of the electron beam column;
condenser electron-optics in the electron beam column for focusing and collimating the electron beam;
an inner electrode in the electron beam column that is positioned in a pupil plane of the electron beam column and has a continuous annular shape surrounding an opening through which the electron beam is transmitted and extending unbroken from an inner circumference to an outer circumference, wherein the optical axis is normal to the pupil plane;
at least one outer electrode positioned in the pupil plane so as to surround the inner electrode;
a two-dimensional array positioned in the pupil plane within the opening of the inner electrode so as to receive the electron beam, wherein the two-dimensional array comprises a blanker array having pixels that are separately controlled to allow or block transmission of electron beamlets so as to form a patterned electron beam; and
circuitry configured to apply an inner voltage level to the inner electrode and at least one outer voltage level to the at least one outer electrode.

18. The electron beam column of claim 17 , further comprising:
projection-electron optics which projects and de-magnifies the electron beam onto a surface of a target substrate.

Assignees

• Kla Tencor Corp

Inventors

• Bevis Christopher F

Classifications

• H01J2237/3175

  Lithography · CPC title

• H01J2237/31789

  Reflection mask · CPC title

• H01J2237/0435

  Multi-aperture · CPC title

• H01J2237/31788

  through mask · CPC title

• H01J37/3007

  Electron or ion-optical systems · CPC title