On-axis illumination and alignment for charge control during charged particle beam inspection

• US 10,168,614 B1
• Filed: 07/06/2017
• Issued: 01/01/2019
• Est. Priority Date: 06/14/2017
• Status: Active Grant

• Current Assignee: Applied Materials Israel Limited (Applied Materials Incorporated), ICT Integrated Circuit Testing Gesellschaft Fur Halbleiterpruftechnik mbH
• Original Assignee: Applied Materials Israel Limited (Applied Materials Incorporated), ICT Integrated Circuit Testing Gesellschaft Fur Halbleiterpruftechnik mbH
• Inventors: Goldenshtein, Alex, Lanio, Stefan
• Primary Examiner(s): Osenbaugh-Stewart, Eliza
• Application Number:
  US15/643,271
• Publication Number:
  US 20180364564A1
• Time in Patent Office: 544 Days
• CPC Class Codes: G03F 1/86 by charged particle beam [CPB]
• CPC Class Codes: G03F 9/7073 Alignment marks and their environment marks specific to masks G03F1/42; marks specific to molds or stamps G03F7/0002; overlay marks G03F7/70633; marks applied to semiconductor devices H01L23/544
• CPC Class Codes: H01J 2237/0047 using electromagnetic radiations, e.g. UV, X-rays, light
• CPC Class Codes: H01J 2237/063 Electron sources
• CPC Class Codes: H01J 2237/30433 System calibration
• CPC Class Codes: H01J 37/026 Means for avoiding or neutralising unwanted electrical charges on tube components
• CPC Class Codes: H01J 37/222 Image processing arrangements associated with the tube
• CPC Class Codes: H01J 37/228 whereby illumination or light collection take place in the same area of the discharge
• CPC Class Codes: H01J 37/28 with scanning beams H01J37/268, H01J37/292, H01J37/2955 take precedence
• CPC Class Codes: H01J 37/3007 Electron or ion-optical systems
• CPC Class Codes: H01J 37/3045 Object or beam position registration
• CPC Class Codes: H01J 37/3174 Particle-beam lithography, e.g. electron beam lithography

Abstract

A charged particle beam apparatus includes a charged particle source configured to generate charged particles, an electrode configured to accelerate the charged particles to form a charged particle beam, a bender unit configured to adjust a path of the charged particle beam, and an objective lens configured to focus the charged particle beam onto a spot on a sample. The charged particle beam passes through a bore of the objective lens as the charged particle beam propagates from the charged particle source to the sample. The apparatus also includes a light source configured to generate a light beam, and a mirror disposed within the bender unit and arranged to direct the light beam to the spot on the sample.

Claims

1. A charged particle beam apparatus, comprising:

a charged particle source configured to generate charged particles;

an electrode configured to accelerate the charged particles to form a charged particle beam;

a bender unit configured to adjust a path of the charged particle beam;

an objective lens configured to focus the charged particle beam onto a spot on a sample, the charged particle beam passing through a bore of the objective lens as the charged particle beam propagates from the charged particle source to the sample;

a light source configured to generate a light beam;

a mirror disposed within the bender unit and arranged to direct the light beam to the spot on the sample;

a sample support configured to support the sample, the sample support having a pinhole extending through a central region; and

a light sensor disposed on an opposite side of the sample support from the objective lens, the light sensor configured to sense light when the light beam is aligned with the pinhole.

2. The apparatus of claim 1 wherein a pointing direction of the light source is adjustable to align the light beam with the spot on the sample.

3. The apparatus of claim 1 wherein a position of the mirror is adjustable to align the light beam with the spot on the sample.

4. The apparatus of claim 1 wherein the path of the charged particle beam is adjustable to scan the charged particle beam on a surface of the sample, and the light source is adjustable to align the light beam with the charged particle beam on the surface of the sample during scanning.

5. The apparatus of claim 1 wherein an axis of the charged particle beam and an axis of the light beam are separated by an angle of less than 3°

to provide substantially on-axis illumination of the spot.

6. The apparatus of claim 1 wherein the mirror is arranged to direct the light beam through the bore of the objective lens and to the spot on the sample.

7. The apparatus of claim 1 wherein the bender unit comprises an unobstructed path that does not block the light beam as the light beam passes through the bender unit.

8. The apparatus of claim 1 further comprising a detector configured to detect charged particles emitted or reflected from the sample.

9. The apparatus of claim 1 wherein a path of the light beam from the mirror to the spot on the sample is substantially normal to a surface of the sample.

10. A method of scanning a sample, the method comprising:

generating charged particles using a charged particle source;

accelerating the charged particles using an electrode to form a charged particle beam;

adjusting a path of the charged particle beam using a bender unit;

focusing the charged particle beam onto a spot on the sample using an objective lens, the charged particle beam passing through a bore of the objective lens as the charged particle beam propagates from the charged particle source to the sample;

generating a light beam using a light source;

directing the light beam through the bore of the objective lens using a mirror disposed within the bender unit, the light beam directed to the spot on the sample; and

adjusting a position of the mirror to align the light beam with the spot on the sample.

11. The method of claim 10 further comprising adjusting a pointing direction of the light source to align the light beam with the spot on the sample.

12. The method of claim 10 further comprising:

adjusting the path of the charged particle beam to scan the charged particle beam on a surface of the sample; and

adjusting an orientation of the light source to align the light beam with the charged particle beam on the surface of the sample during scanning.

13. A method of aligning a charged particle beam of a charged particle apparatus with a light beam, the method comprising:

generating charged particles using a charged particle source;

accelerating the charged particles using an electrode to form the charged particle beam;

adjusting a path of the charged particle beam using a bender unit;

focusing the charged particle beam onto a sample support using an objective lens, the charged particle beam passing through a bore of the objective lens as the charged particle beam propagates from the charged particle source to the sample support;

scanning the charged particle beam across a surface of the sample support;

detecting charged particles emitted or reflected from the sample support during scanning to identify a pinhole in the sample support;

adjusting the path of the charged particle beam to be substantially aligned with the pinhole;

generating the light beam using a light source;

directing the light beam toward the surface of the sample using a mirror disposed within the bender unit;

detecting the light beam using a light sensor when the light beam is aligned with the pinhole; and

adjusting a path of the light beam to be substantially aligned with the pinhole.

14. The method of claim 13 further comprising:

loading a sample onto the sample support;

scanning a surface of the sample with the charged particle beam; and

adjusting the path of the light beam to align the light beam with the charged particle beam on the surface of the sample during scanning.

15. The method of claim 13 wherein the path of the light beam is adjusted by changing a pointing direction of the light source.

16. The method of claim 13 wherein the path of the light beam is adjusted by changing a position of the mirror.

17. The method of claim 13 wherein the charged particle beam and the light beam are separated by an angle of less than 2°

when both are aligned with the pinhole.

18. The method of claim 13 wherein the mirror is arranged to direct the light beam through the bore of the objective lens and to the surface of the sample.