Scanning charged particle beams

• US 8,304,750 B2
• Filed: 12/12/2008
• Issued: 11/06/2012
• Est. Priority Date: 12/17/2007
• Status: Active Grant

• Current Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Inventors: Preikszas, Dirk, Steigerwald, Michael, Ackermann, Joerg
• Primary Examiner(s): NGUYEN, KIET TUAN
• Application Number:
  US12/744,152
• Publication Number:
  US 20100294930A1
• Time in Patent Office: 1,425 Days
• Field of Search: 250/492.22, 250/492.23, 250/398
• US Class Current: 250/492.22
• CPC Class Codes: H01J 2237/004 Charge control of objects or beams
• CPC Class Codes: H01J 2237/022 Avoiding or removing foreign or contaminating particles, debris or deposits on sample or tube
• CPC Class Codes: H01J 2237/0807 Gas field ion sources [GFIS]
• CPC Class Codes: H01J 2237/30488 Raster scan
• CPC Class Codes: H01J 37/026 Means for avoiding or neutralising unwanted electrical charges on tube components
• CPC Class Codes: H01J 37/28 with scanning beams H01J37/268, H01J37/292, H01J37/2955 take precedence
• CPC Class Codes: H01J 37/3026 Patterning strategy

Abstract

Methods are disclosed that include exposing, in direct succession, portions of a surface of a sample to a charged particle beam, the portions of the surface of the sample forming a row in a first direction, the charged particle beam having an average spot size f at the surface of the sample, each portion being spaced from its neighboring portions by a distance of at least d in the first direction, and a ratio d/f being 2 or more.

Claims

1. A method, comprising:

determining a side length F·

√

{square root over (A)} of a smallest square that encloses a region of a sample, wherein A is an area of the region and F is a constant; and

exposing each of M portions of the region of the sample to a charged particle beam, wherein each of the M portions is exposed continuously to the charged particle beam for a time period t₁, a shortest time period between successive exposures of any one of the M portions to the charged particle beam is t₂, and the time periods t₁ and t₂ are selected so that a ratio

2. The method of claim 1, wherein the ratio

3. The method of claim 1, wherein the sample and the charged particle beam are positioned within a common chamber having a gas pressure less than 10⁻

2 Torr, and wherein a plurality of particles leaving the sample are detected by a detector positioned within the common chamber.

4. The method of claim 1, wherein the sample is positioned on a sample mount that permits translation of the sample in a plane orthogonal to a direction of incidence of the charged particle beam, and wherein the mount is configured to permit exchange of the sample for another sample.

5. The method of claim 1, wherein the sample is positioned on a sample mount, and wherein the sample mount is configured to permit adjustment of a distance between the sample and a lens of a charged particle lens system that directs that charged particle beam to be incident on the sample.

6. The method of claim 1, further comprising forming an image of the region based on a plurality of particles leaving the region.

7. The method of claim 6, further comprising displaying the image of the sample to a system operator on an electronic display unit.

8. The method of claim 6, wherein the plurality of particles comprises secondary electrons.

9. The method of claim 6, wherein the plurality of particles comprises at least one member of the group consisting of scattered ions and scattered neutral atoms.

10. The method of claim 6, wherein the plurality of particles comprises photons.

11. The method of claim 1, further comprising exposing the region to an electron source prior to exposing the region to the charged particle beam.

12. The method of claim 1, further comprising exposing the region to an electron source during exposure of the region to the charged particle beam.

13. The method of claim 1, wherein a charged particle current of the charged particle beam is 10 pA or more.

14. The method of claim 13, wherein the charged particle current is 100 pA or more.

15. The method of claim 1, wherein each of the M portions of the region is exposed to the charged particle beam for an exposure time of 100 μ

s or less.

16. The method of claim 1, wherein a charged particle current of the charged particle beam is 1 pA or more, each of the M portions is exposed to the charged particle beam for an exposure time of 100 μ

s or less, and an image of the sample is formed over a total acquisition time of 100 seconds or less.

17. The method of claim 1, wherein the charged particle beam comprises noble gas ions.

18. The method of claim 17, wherein the noble gas ions comprise helium ions.

19. The method of claim 1, wherein the charged particle beam comprises electrons.

20. The method of claim 1, wherein the charged particle beam has an energy spread at the surface of the sample of five eV or less.

21. The method of claim 1, wherein a resolution of the image is three nm or less.

22. The method of claim 1, wherein the charged particle beam is produced by a gas field ion microscope having a quality factor of 0.25 or more.

23. The method of claim 1, wherein each of the M portions comprises multiple image pixels.

24. The method of claim 1, further comprising heating the region during exposure to the charged particle beam.

25. The method of claim 1, wherein the charged particle beam has a reduced brightness at a surface of the sample of 5×

10⁸ A/m²srV or more.

26. The method of claim 1, wherein determining the side length of the smallest square comprises determining a maximum dimension of the region.

27. The method of claim 1, further comprising exposing, in direct succession, a first plurality of the M portions to the charged particle beam, the first plurality of portions forming a row in a first direction, the charged particle beam having an average spot size f at a surface of the sample, each portion of the first plurality of portions being spaced from its neighboring portions by a distance of at least d in the first direction, and a ratio d/f being 2 or more.

28. The method of claim 27, further comprising exposing, in direct succession, a second plurality of the M portions to the charged particle beam, the second plurality of portions forming a row in the first direction parallel to the row formed by the first plurality of portions, each portion of the second plurality of portions being spaced from its neighboring portions in the second plurality of portions by a distance of at least d in the first direction and being spaced from the first plurality of portions by a distance of at least e in a second direction orthogonal to the first direction.

29. The method of claim 28, wherein e is larger than d.

30. The method of claim 28, wherein f is 5 nm or less, d is 10 nm or more, and e is 10 nm or more.