Particle source with selectable beam current and energy spread

• US 20050178982A1
• Filed: 02/15/2005
• Published: 08/18/2005
• Est. Priority Date: 02/17/2004
• Status: Active Grant

• Current Assignee: FEI Company (Thermo Fisher Scientific Incorporated)
• Original Assignee: FEI Company (Thermo Fisher Scientific Incorporated)
• Inventors: Henstra, Alexander, Chmelik, Jaroslav
• Granted Patent: US 7,034,315 B2
• Time in Patent Office: Days
• US Class Current: 250/492.220
• CPC Class Codes: H01J 37/05 Electron or ion-optical arrangements for separating electrons or ions according to their energy or massparticle separator tubes H01J49/00
• CPC Class Codes: H01J 37/09 Diaphragms; Shields associated with electron or ion-optical arrangements; Compensation of disturbing fields
• CPC Class Codes: H01J 37/153 Electron-optical or ion-optical arrangements for the correction of image defects, e.g. stigmators
• CPC Class Codes: H01J 37/26 Electron or ion microscopes; Electron or ion diffraction tubes

Abstract

The invention describes a particle source in which energy selection occurs. The energy selection occurs by sending a beam of electrically charged particles 13 eccentrically through a lens 6. As a result of this, energy dispersion will occur in an image 15 formed by the lens 6. By projecting this image 15 onto a diaphragm 7, it is possible to only allow particles in a limited portion of the energy spectrum to pass. Consequently, the passed beam 16 will have a reduced energy spread. By adding a deflection unit 10, this particle beam 16 can be deflected toward the optical axis 2. One can also elect to deflect a beam 12 going through the middle of the lens 6—and having, for example, greater current—toward the optical axis.

Claims

1. A particle-optical apparatus equipped with a particle source, which particle source is embodied to generate at least one beam of electrically charged particles (16) and which particle source is provided with:

a particle-emitting surface for emission of the electrically charged particles;

a lens for formation of an image of the particle-emitting surface;

a beam-limiting diaphragm for limitation of said beam of particles, and;

an energy-selecting diaphragm at the location of the image, characterized in that

the beam-limiting diaphragm is embodied in such a way that said beam is a beam that goes through the lens eccentrically.

2. A particle-optical apparatus according to claim 1, in which the beam-limiting diaphragm is also embodied to allow a beam going through the middle of the lens to pass.

3. A particle-optical apparatus according to claim 1, provided with a deflection unit, which deflection unit is embodied to deflect one of the beams of electrically charged particles toward an optical axis, in such a manner than this beam further propagates about the optical axis.

4. A particle-optical apparatus according to claim 1, in which the particle-emitting surface has the form of several, non-juxtaposed, particle-emitting constituent surfaces.

6. A particle-optical apparatus according to claim 2, provided with a deflection unit, which deflection unit is embodied to deflect one of the beams of electrically charged particles toward an optical axis, in such a manner than this beam further propagates about the optical axis.

7. A particle-optical apparatus according to claim 2, in which the particle-emitting surface has the form of several, non-juxtaposed, particle-emitting constituent surfaces.

8. A particle-optical apparatus according to claim 3, in which the particle-emitting surface has the form of several, non-juxtaposed, particle-emitting constituent surfaces.

9. A particle-optical apparatus according to claim 6, in which the particle-emitting surface has the form of several, non-juxtaposed, particle-emitting constituent surfaces.

5. A particle source for use in a particle-optical apparatus, the particle source configured to generate at least one beam of electrically charged particles, the particle source comprising:

a particle-emitting surface for emission of the electrically charged particles;

a lens for formation of an image of the particle-emitting surface;

a beam-limiting diaphragm for limitation of said beam of particles, the beam-limiting diaphragm is embodied in such a way that said beam is a beam that goes through the lens eccentrically; and

an energy-selecting diaphragm at the location of the image.

10. A particle-optical source according to claim 5, in which the beam-limiting diaphragm is also embodied to allow a beam going through the middle of the lens to pass.

11. A particle-optical source according to claim 5, provided with a deflection unit, which deflection unit is embodied to deflect one of the beams of electrically charged particles toward an optical axis, in such a manner than this beam further propagates about the optical axis.

12. A particle-optical source according to claim 10, provided with a deflection unit, which deflection unit is embodied to deflect one of the beams of electrically charged particles toward an optical axis, in such a manner than this beam further propagates about the optical axis.

13. A particle-optical source according to claim 5, in which the particle-emitting surface has the form of several, non-juxtaposed, particle-emitting constituent surfaces.

14. A particle-optical source according to claim 10, in which the particle-emitting surface has the form of several, non-juxtaposed, particle-emitting constituent surfaces.

15. A particle-optical source according to claim 11, in which the particle-emitting surface has the form of several, non-juxtaposed, particle-emitting constituent surfaces.

16. A particle-optical source according to claim 12, in which the particle-emitting surface has the form of several, non-juxtaposed, particle-emitting constituent surfaces.