Method and system for aberration correction in an electron beam system

Patent metadata

Field	Value
Publication number	US-10090131-B2
Application number	US-201615371557-A
Country	US
Kind code	B2
Filing date	Dec 7, 2016
Priority date	Dec 7, 2016
Publication date	Oct 2, 2018
Grant date	Oct 2, 2018

Abstract

An electron-optical system for performing electron microscopy is disclosed. The system includes an electron beam source configured to generate a primary electron beam. The system includes a source lens, a condenser lens and an objective lens disposed along an optical axis. The system includes a first Wien filter disposed along the optical axis and a second Wien filter disposed along the optical axis. The first Wien filter and the second Wien filter are disposed between the source lens and the objective lens. The first Wien filter is configured to correct chromatic aberration in the primary beam. The system also includes a detector assembly configured to detect electrons emanating from the surface of the sample.

First claim

What is claimed:

1. An electron-optical system comprising:
an electron beam source configured to generate a primary electron beam;
a sample stage configured to secure a sample;
a set of electron-optical elements configured to direct at least a portion of the primary electron beam onto a portion of the sample, the set of electron-optical elements comprising:
a source lens disposed along an optical axis;
a condenser lens disposed along the optical axis;
an objective lens disposed along the optical axis;
a first deflector assembly disposed along the optical axis; and
a second deflector assembly disposed along the optical axis, the first deflector assembly and the second deflector assembly are disposed between the source lens and the objective lens, wherein the first deflector assembly is configured to correct chromatic aberration in the primary beam, wherein at least one of the first deflector assembly or the second deflector assembly comprises a Wien filter; and

a detector assembly configured to detect electrons emanating from the surface of the sample.

2. The apparatus of claim 1 , wherein the first deflector assembly and the second deflector assembly are disposed between the condenser lens and the objective lens.

3. The apparatus of claim 1 , wherein the first deflector assembly is disposed between the source lens and the condenser lens and the second deflector assembly is disposed between the condenser lens and the objective lens.

4. The apparatus of claim 1 , wherein the first deflector assembly is configured to correct chromatic aberration in the primary beam caused by one or more portions of the set of electron-optical elements.

5. The apparatus of claim 1 , wherein the second deflector assembly is configured to direct electrons emanating from the sample to the detector assembly.

6. The apparatus of claim 5 , wherein the second deflector assembly is configured to direct secondary electrons emanating from the sample to the detector assembly.

7. The apparatus of claim 1 , wherein the primary electron beam comprises:
a telecentric electron beam.

8. The apparatus of claim 7 , wherein the strength of the first deflector assembly is equal to the strength of the second deflector assembly.

9. The apparatus of claim 8 , wherein the polarity of the first deflector assembly is reversed relative to the polarity of the second deflector assembly.

10. The apparatus of claim 1 , wherein the primary electron beam comprises:
a divergent electron beam.

11. The apparatus of claim 10 , wherein the strength of the first deflector assembly is larger than the strength of the second deflector assembly.

12. The apparatus of claim 11 , wherein the polarity of the first deflector assembly is reversed relative to the polarity of the second deflector assembly.

13. The apparatus of claim 1 , wherein the primary electron beam comprises:
a convergent electron beam.

14. The apparatus of claim 13 , wherein the strength of the first deflector assembly is smaller than the strength of the second deflector assembly.

15. The apparatus of claim 14 , wherein the polarity of the first deflector assembly is reversed relative to the polarity of the second deflector assembly.

16. The apparatus of claim 1 , wherein the primary electron beam comprises:
a cross-over electron beam.

17. The apparatus of claim 16 , wherein the polarity of the first deflector assembly is the same as the polarity of the second deflector assembly.

18. The apparatus of claim 17 , wherein the strength of the first deflector assembly is equal to the strength of the second deflector assembly.

19. The apparatus of claim 17 , wherein the strength of the first deflector assembly is larger than the strength of the second deflector assembly.

20. The apparatus of claim 17 , wherein the strength of the first deflector assembly is smaller than the strength of the second deflector assembly.

21. The apparatus of claim 1 , wherein the electron beam source comprises:
one or more electron guns.

22. The apparatus of claim 1 , wherein the detector assembly comprises:
one or more secondary electron detectors.

23. An electron-optical system comprising:
an electron beam source configured to generate a primary electron beam;
a source lens disposed along an optical axis;
a condenser lens disposed along the optical axis;
an objective lens disposed along the optical axis;
a first Wien filter disposed along the optical axis;
a second Wien filter disposed along the optical axis, the first Wien filter and the second Wien filter are disposed between the source lens and the objective lens, wherein the first Wien filter is configured to correct chromatic aberration in the primary beam; and
a detector assembly configured to detect electrons emanating from the surface of the sample.

24. The apparatus of claim 23 , wherein the first Wien filter and the second Wien filter are disposed between the condenser lens and the objective lens.

25. The apparatus of claim 23 , wherein the first Wien filter is disposed between the source lens and the condenser lens and the second Wien filter is disposed between the condenser lens and the objective lens.

26. The apparatus of claim 23 , wherein the first Wien filter is configured to correct chromatic aberration in the primary beam caused by one or more portions of the set of electron-optical elements.

27. The apparatus of claim 23 , wherein the second Wien filter is configured to direct secondary electrons emanating from the sample to a detector assembly.

28. The apparatus of claim 23 , wherein the primary electron beam comprises:
a telecentric electron beam.

29. The apparatus of claim 28 , wherein the strength of the first Wien filter is equal to the strength of the second Wien filter.

30. The apparatus of claim 29 , wherein the polarity of the first Wien filter is reversed relative to the polarity of the second Wien filter.

31. The apparatus of claim 23 , wherein the primary electron beam comprises:
a divergent electron beam.

32. The apparatus of claim 31 , wherein the strength of the first Wien filter is larger than the strength of the second Wien filter.

33. The apparatus of claim 32 , wherein the polarity of the first Wien filter is reversed relative to the polarity of the second Wien filter.

34. The apparatus of claim 23 , wherein the primary electron beam comprises:
a convergent electron beam.

35. The apparatus of claim 34 , wherein the strength of the first Wien filter is smaller than the strength of the second Wien filter.

36. The apparatus of claim 35 , wherein the polarity of the first Wien filter is reversed relative to the polarity of the second Wien filter.

37. The apparatus of claim 23 , wherein the primary electron beam comprises:
a cross-over electron beam.

38. The apparatus of claim 37 , wherein the polarity of the first deflector assembly is the same as the polarity of the second deflector assembly.

39. The apparatus of claim 38 , wherein the strength of the first Wien filter is equal to the strength of the second Wien filter.

40. The apparatus of claim 38 , wherein the strength of the first Wien filter is larger th

Assignees

• Kla Tencor Corp

Inventors

• Jiang Xinrong
• Sears Christopher

Classifications

• H01J37/28 Primary

  with scanning beams {(H01J37/268, H01J37/292, H01J37/2955 take precedence)} · CPC title

• H01J37/05

  Electron or ion-optical arrangements for separating electrons or ions according to their energy {or mass}(particle separator tubes H01J49/00) · CPC title

• H01J37/153 Primary

  Electron-optical or ion-optical arrangements for the correction of image defects, e.g. stigmators · CPC title

• H01J2237/28

  Scanning microscopes · CPC title

• H01J37/10

  Lenses · CPC title