High resolution electron beam apparatus with dual-aperture schemes

Patent metadata

Field	Value
Publication number	US-11508591-B2
Application number	US-202117170871-A
Country	US
Kind code	B2
Filing date	Feb 8, 2021
Priority date	Feb 8, 2021
Publication date	Nov 22, 2022
Grant date	Nov 22, 2022

Abstract

An electron source emits an electron beam. The electron beam is received by a beam limiting assembly. The beam limiting assembly has a first beam limiting aperture with a first diameter and a second beam limiting aperture with a second diameter larger than the first diameter. The first beam limiting aperture receives the electron beam. This beam limiting assembly reduces the influence of Coulomb interactions.

First claim

What is claimed is:

1. A system comprising:
an electron source configured to emit an electron beam;
a suppression electrode disposed proximate the electron source;
an extraction electrode disposed proximate the electron source;
a beam limiting assembly defining a first beam limiting aperture with a first diameter, a second beam limiting aperture with a second diameter, and a channel between the first beam limiting aperture and the second beam limiting aperture, wherein the channel has a third diameter larger than that of the first diameter of the first beam limiting aperture and the second diameter of the second beam limiting aperture, wherein the beam limiting assembly is positioned to receive the electron beam in the first beam limiting aperture, and wherein the first diameter is from 1.5 to 5.0 times larger than the second diameter; and
at least one pole piece disposed adjacent the beam limiting assembly.

2. The system of claim 1 , wherein the beam limiting assembly includes a flange on a surface of the beam limiting assembly that receives the electron beam from the electron source, wherein the flange is disposed between the electron source and the at least one pole piece.

3. The system of claim 1 , wherein the first beam limiting aperture is disposed closer to the electron source than the second beam limiting aperture.

4. The system of claim 1 , wherein the beam limiting aperture further includes a transition region between the first beam limiting aperture and the channel, wherein the transition region has a diameter that increases from the first diameter to the third diameter, and wherein the transition region has a length along the direction of the electron beam that is from 1 mm to 10 mm.

5. The system of claim 4 , wherein the third diameter is configured to stop a majority of the secondary electrons without clipping the primary electrons.

6. The system of claim 1 , further comprising an objective lens, an aperture disposed in a path of the electron beam between the beam limiting assembly and the objective lens, and a condenser lens disposed in the path of the electron beam between the aperture and the beam limiting assembly.

7. The system of claim 1 , further comprising an objective lens, an aperture disposed in a path of the electron beam between the beam limiting assembly and the objective lens, and a condenser lens disposed in the path of the electron beam between the aperture and the objective lens.

8. The system of claim 1 , wherein the beam limiting assembly defines a recess on the surface that receives the electron beam from the electron source, wherein the first beam limiting aperture is disposed in a base of the recess, and wherein the recess has a fourth diameter that is larger than the first diameter and the second diameter.

9. The system of claim 1 , wherein the second beam limiting aperture is spaced apart from the first beam limiting aperture from 5 mm to 10 mm along a path of the electron beam.

10. The system of claim 1 , wherein the third diameter is approximately 1 mm in diameter and a length of the channel is from 6 mm to 12 mm.

11. A method comprising:
forming an electron beam; and
directing the electron beam through a beam limiting assembly, wherein the beam limiting assembly defines a first beam limiting aperture with a first diameter, a second beam limiting aperture with a second diameter, and a channel between the first beam limiting aperture and the second beam limiting aperture, wherein the channel has a third diameter larger than that of the first diameter of the first beam limiting aperture and the second diameter of the second beam limiting aperture, wherein the beam limiting assembly is positioned to receive the electron beam in the first beam limiting aperture, and wherein the first diameter is from 1.5 to 5.0 times larger than the second diameter.

12. The method of claim 11 , further comprising focusing the electron beam to form a crossover after the electron beam exits the beam limiting assembly.

13. The method of claim 11 , further comprising defocusing the electron beam after the electron beam exits the beam limiting assembly.

14. The method of claim 11 , wherein a beam current of the electron beam is from 1 nA to 100 nA.

15. The method of claim 11 , further comprising directing the electron beam through a condenser lens that is activated and disposed downstream along a path of the electron beam from the beam limiting assembly, an aperture disposed downstream along the path of the electron beam from the condenser lens, and an objective lens disposed downstream along the path of the electron beam from the aperture.

16. The method of claim 15 , wherein a beam current of the electron beam is from 0.1 nA to 20 nA or from 60 nA to 500 nA.

17. The method of claim 11 , further comprising directing the electron beam through an aperture disposed downstream along a path of the electron beam from the beam limiting assembly, a condenser lens that is activated and disposed downstream along the path of the electron beam from the aperture, and an objective lens disposed downstream along the path of the electron beam from the condenser lens.

18. The method of claim 17 , wherein a beam current of the electron beam is from 20 nA to 60 nA.

19. The method of claim 11 , further comprising directing the electron beam to a surface of a semiconductor wafer, wherein a beam current selected by the second beam limiting aperture is equal to a beam current at the surface of the semiconductor wafer.

20. The method of claim 11 , further comprising directing the electron beam through a recess on a surface of the beam limiting assembly that receives the electron beam from the electron source, wherein the first beam limiting aperture is disposed in a base of the recess, and wherein the recess has a fourth diameter that is larger than the first diameter and the second diameter.

21. The method of claim 11 , wherein the electron beam passes through the channel, and wherein the third diameter is configured to stop a majority of secondary electrons without clipping primary electrons.

Assignees

• Kla Corp

Inventors

• Jiang Xinrong
• Sears Christopher
• Chubun Nikolai
• Grella Luca

Classifications

• H10P72/0616 Primary

  Monitoring of warpages, curvatures, damages, defects or the like · CPC title

• G01N2223/6116

  semiconductor wafer · CPC title

• H01J37/147

  Arrangements for directing or deflecting the discharge along a desired path ({H01J37/045 take precedence;} lenses H01J37/10) · CPC title

• H01J2237/083

  Beam forming · CPC title

• H01J37/063 Primary

  Geometrical arrangement of electrodes for beam-forming · CPC title