Notched magnetic lens for improved sample access in an SEM

Patent metadata

Field	Value
Publication number	US-9443693-B2
Application number	US-201514738632-A
Country	US
Kind code	B2
Filing date	Jun 12, 2015
Priority date	Sep 23, 2013
Publication date	Sep 13, 2016
Grant date	Sep 13, 2016

Abstract

A magnetic immersion lens apparatus includes an outer pole piece and an inner pole piece with a gap therebetween. The outer pole piece has an opening that permits energetic particles from a target in front of the immersion lens to pass through the outer pole piece to an external detector. The outer or inner pole piece has one or more notches near the gap. This abstract is provided to comply with rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

First claim

What is claimed is:

1. A system, comprising:
a charged particle optical column configured to generate a primary beam of charged particles and focus the primary beam onto a target, the charged particle optical column including a magnetic immersion lens, the magnetic immersion lens having an outer pole piece and an inner pole piece with a gap therebetween, the outer pole piece having an opening that permits energetic particles from the target to pass through the outer pole piece to an external detector, wherein the inner or outer pole piece has one or more notches proximate the gap.

2. The system of claim 1 , wherein the one or more notches include two or more notches arranged in an axially symmetric pattern with respect to the axis of the charged particle column.

3. The system of claim 1 , wherein the one or more notches include three or more notches arranged in an axially symmetric pattern with respect to the axis of the charged particle column.

4. The system of claim 1 , wherein the one or more notches include four or more notches arranged in an axially symmetric pattern with respect to the axis of the charged particle column.

5. The system of claim 1 , wherein the notches are large enough to provide a desired access for the detector to the target without increasing power needed to drive the immersion lens by more than 1%.

6. The system of claim 1 , wherein the outer pole piece has a number of notches proximate the gap.

7. The system of claim 1 , wherein the inner pole piece has a number of notches proximate the gap.

8. The system of claim 1 , wherein both the inner pole piece and the outer pole piece have a number of notches proximate the gap.

9. The system of claim 1 , wherein the gap is a radial gap.

10. The system of claim 1 , wherein the gap is an axial gap.

11. The system of claim 1 , further comprising the external detector.

12. The system of claim 11 , wherein the external detector is an X-ray detector.

13. The system of claim 12 , wherein the charged particle optical column is configured to generate a primary beam of electrons and focus the primary beam of electrons onto the target.

14. A magnetic immersion lens apparatus, comprising:
an outer pole piece and an inner pole piece with a gap therebetween, the outer pole piece having an opening that permits energetic particles from a target in front of the immersion lens to pass through the outer pole piece to an external detector, wherein the outer or inner pole piece has one or more notches proximate the gap.

15. The apparatus of claim 14 , wherein the one or more notches include two or more notches arranged in an axially symmetric pattern with respect to an axis of a charged particle column.

16. The apparatus of claim 14 , wherein the one or more notches include four or more notches arranged in an axially symmetric pattern with respect to an axis of a charged particle column.

17. The apparatus of claim 14 , wherein the notches are large enough to provide a desired access for the detector to the target without increasing power needed to drive the immersion lens by more than 1%.

18. The apparatus of claim 14 , wherein the outer pole piece has a number of notches proximate the gap.

19. The apparatus of claim 14 , wherein the inner pole piece has a number of notches proximate the gap.

20. The apparatus of claim 14 , wherein both the inner pole piece and the outer pole piece have a number of notches proximate the gap.

21. The apparatus of claim 14 , wherein the gap is a radial gap.

22. The apparatus of claim 14 , wherein the gap is an axial gap.

23. An outer pole piece for a magnetic immersion lens, the outer pole piece having an opening that permits energetic particles from a target in front of the immersion lens to pass through the outer pole piece to an external detector, wherein the outer pole piece has one or more notches proximate a central aperture.

Assignees

• Kla Tencor Corp

Inventors

• Sears Christopher M

Classifications

• H01J2237/1415

  Bores or yokes, i.e. magnetic circuit in general · CPC title

• H01J2237/1405

  Constructional details · CPC title

• H01J37/28

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

• H01J2237/2807

  X-rays · CPC title

• H01J37/141 Primary

  Electromagnetic lenses · CPC title