Focusing a charged particle system

Patent metadata

Field	Value
Publication number	US-9530613-B2
Application number	US-201214000213-A
Country	US
Kind code	B2
Filing date	Feb 17, 2012
Priority date	Feb 18, 2011
Publication date	Dec 27, 2016
Grant date	Dec 27, 2016

Abstract

A charged particle beam focusing apparatus includes a charged particle beam generator configured to project simultaneously at least one non-astigmatic charged particle beam and at least one astigmatic charged particle beam onto locations on a surface of a specimen, thereby causing released electrons to be emitted from the locations. The apparatus also includes an imaging detector configured to receive the released electrons from the locations and to form images of the locations from the released electrons. A processor analyzes the image produced by the at least one astigmatic charged particle beam and in response thereto adjusts a focus of the at least one non-astigmatic charged particle beam.

First claim

What is claimed is:

1. A method comprising:
producing simultaneously at least one non-astigmatic charged particle beam and at least one astigmatic charged particle beam;
forming, from the at least one non-astigmatic charged particle beam, a corresponding set of images of a surface;
forming, from the at least one astigmatic charged particle beam, a corresponding set of images of the surface; and
focusing, by a processor, the at least one non-astigmatic charged particle beam using the set of images that correspond to the at least one astigmatic charged particle beam.

2. The method of claim 1 , wherein producing simultaneously the at least one non-astigmatic charged particle beam and the at least one astigmatic charged particle beam comprises:
projecting a plurality of charged particle beams through a set of apertures in the multi-aperture array to produce the at least one astigmatic charged particle beam; and
projecting the plurality of charged particle beams through another set of apertures in the multi-aperture array to produce the at least one non-astigmatic charged particle beam, wherein the set of apertures to produce the at least one astigmatic charged particle beam are in a position further from an optical axis than the other set of apertures to produce the at least one non-astigmatic charged particle beam.

3. The method of claim 1 , wherein producing simultaneously the at least one non-astigmatic charged particle beam and the at least one astigmatic charged particle beam comprises:
projecting a plurality of charged particle beams through a set of apertures in the multi-aperture array to produce the at least one astigmatic charged particle beam; and projecting the plurality of charged particle beams through another set of apertures in the multi-aperture array to produce the at least one non-astigmatic charged particle beam, wherein the set of apertures to produce the at least one astigmatic charged particle beam are at a radial distance that is 2 to 3 times further from an optical axis than a radial distance of at least some of the other set of apertures to produce the at least one non-astigmatic charged particle beam.

4. A method comprising:
producing simultaneously a plurality of non-astigmatic charged particle beams and a plurality of astigmatic charged particle beams;
applying different potentials by a defocus multi-aperture array to reduce a number of astigmatic charged particle beams in the plurality of astigmatic charged particle beams;
forming, from the plurality of non-astigmatic charged particle beams, a corresponding set of images of a surface;
forming, from the reduced number of astigmatic charged particle beams, a corresponding set of images of the surface; and
focusing, by a processor, the plurality of non-astigmatic charged particle beams using the set of images that correspond to the reduced number of astigmatic charged particle beams.

5. The method according to claim 4 , wherein the different potentials comprise a potential different than that of a multi-aperture array.

6. The method of claim 4 , wherein focusing the set of images that correspond to the plurality of non-astigmatic charged particle beams comprises:
varying amounts of defocus on the reduced number of astigmatic charged particle beams to gather focus information for the varying amounts of defocus.

7. The method of claim 4 , wherein producing simultaneously a plurality of non-astigmatic charged particle beams and a plurality of astigmatic charged particle beams comprises:
limiting a beam current via apertures in a pre-multi-aperture array element.

8. A beam source for an imaging system, comprising:
a charged particle source; and
a multi-aperture array coupled to the charged particle source and positioned to receive a plurality of charged particle beams produced by the charged particle source to simultaneously produce at least one non-astigmatic charged particle beam and at least one astigmatic charged particle beam, the at least one non-astigmatic charged particle beam forming a corresponding set of images of a surface and the at least one astigmatic charged particle beam forming a corresponding set of images of the surface, wherein the imaging system is configured so that the set of images that correspond to the at least one astigmatic charged particle beam is used to focus the at least one non-astigmatic charged particle beam.

9. The beam source for the imaging system of claim 8 , wherein the multi-aperture array comprises apertures to produce the at least one astigmatic charged particle beam and apertures to produce the at least one non-astigmatic charged particle beam, the apertures to produce the at least one astigmatic charged particle beam being in a position further from an optical axis than the apertures to produce the at least one non-astigmatic charged particle beam.

10. The beam source for the imaging system of claim 8 , wherein the multi-aperture array comprises apertures to produce the at least one astigmatic charged particle beam and apertures to produce the at least one non-astigmatic charged particle beam, the apertures to produce the at least one astigmatic charged particle beam being in a position at a radial distance that is 2 to 3 times further from the optical axis than a radial distance of at least some of the apertures in the multi-aperture array used to produce the at least one non-astigmatic charged particle beam.

11. The beam source for the imaging system of claim 8 , wherein the multi-aperture array comprises apertures to produce the at least one astigmatic charged particle beam and apertures to produce the at least one non-astigmatic charged particle beam, the apertures to produce the at least one astigmatic charged particle beam being larger than the apertures in the multi-aperture array used to produce the at least one non-astigmatic charged particle beam.

12. The beam source for the imaging system of claim 11 , further comprising a pre-multi-aperture array element positioned between the charged particle source and the multi-aperture array, the pre-multi-aperture array element comprising apertures that smaller than the apertures in the multi-aperture array which are used to produce the at least one astigmatic charged particle beam.

13. The beam source for the imaging system of claim 12 , wherein the pre-multi-aperture array element further comprises apertures that are smaller than the apertures in the multi-aperture array which are used to produce the at least one non-astigmatic charged particle beam.

14. A beam source for an imaging system, comprising:
a charged particle source;
a multi-aperture array coupled to the charged particle source and positioned to receive a plurality of charged particle beams produced by the charged particle source to simultaneously produce a plurality of non-astigmatic charged particle beams and a plurality of astigmatic charged particle beams and
a dynamic defocus multi-aperture array coupled to the multi-aperture array to reduce a number of astigmatic charged particle beams in the plurality of astigmatic charged particle beams, the plurality of non-astigmatic charged particle beams resulting in a corresponding set of images of a surface and the reduced number of astigmatic charged particle beams resulting in a corresponding set of images of the surface, wherein the imaging system is configured so that the set of images that correspond to the reduced number of astigmatic charged particle beams is used to focus the plurality of non-astigmatic charged particle beams.

15. The beam source for an imaging system of claim 14 , wherein the dynamic defocus multi-apertu

Assignees

• Rogers Steven R
• Knippelmeyer Rainer K
• Kemen Thomas
• Schubert Stefan
• Elmaliah Nissim
• Applied Materials Israel Ltd
• Zeiss Carl Microscopy Gmbh

Inventors

• Rogers Steven R
• Knippelmeyer Rainer K
• Kemen Thomas
• Schubert Stefan
• Elmaliah Nissim

Classifications

• H01J37/222

  Image processing arrangements associated with the tube · CPC title

• H01J2237/0453

  multiple apertures · CPC title

• H01J2237/2817

  Pattern inspection · CPC title

• H01J37/244

  Detectors; Associated components or circuits therefor · CPC title

• H01J37/22

  Optical {, image processing} or photographic arrangements associated with the tube · CPC title