Twin beam charged particle column and method of operating thereof

• US 8,378,299 B2
• Filed: 03/10/2011
• Issued: 02/19/2013
• Est. Priority Date: 03/10/2010
• Status: Active Grant

• Current Assignee: ICT Integrated Circuit Testing Gesellschaft Fur Halbleiterpruftechnik mbH
• Original Assignee: ICT Integrated Circuit Testing Gesellschaft Fur Halbleiterpruftechnik mbH
• Inventors: Frosien, Jrgen
• Primary Examiner(s): Vanore, David A
• Application Number:
  US13/045,068
• Publication Number:
  US 20110220795A1
• Time in Patent Office: 712 Days
• Field of Search: 250/309, 250/310, 250/311
• US Class Current: 250/311
• CPC Class Codes: H01J 2237/0453 multiple apertures
• CPC Class Codes: H01J 2237/04756 with electrostatic means
• CPC Class Codes: H01J 2237/1514 Prisms
• CPC Class Codes: H01J 2237/153 Correcting image defects, e.g. stigmators
• CPC Class Codes: H01J 2237/24465 Sectored detectors, e.g. quadrants
• CPC Class Codes: H01J 2237/24592 Inspection and quality control of devices
• CPC Class Codes: H01J 2237/2817 Pattern inspection
• CPC Class Codes: H01J 37/147 Arrangements for directing or deflecting the discharge along a desired path H01J37/045 take precedence; lenses H01J37/10
• CPC Class Codes: H01J 37/1471 for centering, aligning or positioning of ray or beam
• CPC Class Codes: H01J 37/244 Detectors; Associated components or circuits therefor
• CPC Class Codes: H01J 37/28 with scanning beams H01J37/268, H01J37/292, H01J37/2955 take precedence

Abstract

A column for a charged particle beam device is described. The column includes a charged particle emitter for emitting a primary charged particle beam as one source of the primary charged particle beam; a biprism adapted for acting on the primary charged particle beam so that two virtual sources are generated; and a charged particle beam optics adapted to focus the charged particle beam simultaneously on two positions of a specimen corresponding to images of the two virtual sources.

Claims

1. A column for a charged particle beam device, said column comprising:

a charged particle emitter for emitting a primary charged particle beam as one source of the primary charged particle beam;

a biprism adapted for acting on the primary charged particle beam so that two virtual sources are generated;

a charged particle beam optics adapted to focus the charged particle beam simultaneously on two positions of a specimen corresponding to images of the two virtual sources;

a beam separator for separating the primary charged particle beam and particles selected from the group consisting of secondary particles coming from the specimen, backscattered particles coming from the specimen, and secondary particles and backscattered particles coming from the specimen; and

at least one detector for measuring the particles selected from the group consisting of secondary particles coming from the specimen, backscattered particles coming from the specimen, and secondary particles and backscattered particles coming from the specimen.

2. The column according to claim 1, further comprising:

an aperture plate having at least two apertures to produce at least two sub-beams of the primary charged particle beam.

3. The column according to claim 1, wherein the biprism comprises a wire or rod.

4. The column according to claim 3, wherein the wire or rod:

is disposed between a pair of electrostatic plates,

extends substantially cylindrically in one direction, or

is disposed between a pair of electrostatic plates and extends substantially cylindrically in one direction.

5. The column according to claim 1,

wherein the detector is positioned between the emitter and an objective lens of the charged particle beam optics and comprises at least one opening to let the beams of charged particles pass through.

6. The column according to claim 5, wherein the objective lens is adapted to guide the particles selected from the group consisting of:

secondary particles, backscattered particles; and

secondary particles and backscattered particles;

onto the detector.

7. The column according to claim 6, wherein the objective lens comprises a magnetic lens and an electrostatic lens.

8. The column according to claim 1, wherein the detector is subdivided into two or more segments.

9. The column according to claim 1, wherein a first electrode and means for applying a first potential to said first electrode are provided and wherein a second electrode and means for applying a second potential to said second electrode are provided to generate an electrical field in said charged particle beam optics so that the particle beams in said electrical field are decelerated from a first energy to a second lower energy.

10. The column according to claim 9, wherein the column is configured for the second lower energy being 5 kV or below.

11. The column according to claim 1, wherein, by the combined action of the biprism and the charged particle optics, the beams are tilted and hit the specimen with predetermined angles of incidence.

12. The column according to claim 1, wherein the column comprises at least one aberration correction unit adapted to correct one or more types of aberrations selected from the group consisting of:

spherical and chromatic aberrations.

13. The column according to claim 1, further comprising:

a biprism configured for increasing the beam separation of bundles of signal electrons.

14. A charged particle beam device, comprising:

a charged particle beam column wherein the charged particle beam device is an electron inspection tool, and wherein said column comprises;

a charged particle emitter for emitting a primary charged particle beam as one source of the primary charged particle beam;

a biprism adapted for acting on the primary charged particle beam so that two virtual sources are generated;

a charged particle beam optics adapted to focus the charged particle beam simultaneously on two positions of a specimen corresponding to images of the two virtual sources;

a beam separator for separating the primary charged particle beam and particles selected from the group consisting of secondary particles coming from the specimen, backscattered particles coming from the specimen, and secondary particles and backscattered particles coming from the specimen; and

at least one detector for measuring the particles selected from the group consisting of secondary particles coming from the specimen, backscattered particles coming from the specimen, and secondary particles and backscattered particles coming from the specimen.

15. A method of operating a charged particle beam column, the method comprising:

emitting a charged particle beam from one source;

generating two sub-beams with a biprism;

focusing the two sub-beams on two positions of a specimen such that images of two virtual sources are generated;

separating, by a beam separator, the primary charged particle beam and particles selected from the group consisting of secondary particles coming from the specimen, backscattered particles coming from the specimen, and secondary particles and backscattered particles coming from the specimen; and

measuring the particles selected from the group consisting of secondary particles coming from the specimen, backscattered particles coming from the specimen, and secondary particles and backscattered particles coming from the specimen with at least one detector.

16. The method according to claim 15, wherein the biprism comprises a wire or rod extending in a first direction and the virtual sources are generated to be located in a plane perpendicular to the first direction.