Interferometer, exposure apparatus, exposure method and interference length measurement method

• US 20030223076A1
• Filed: 02/25/2003
• Published: 12/04/2003
• Est. Priority Date: 02/27/2002
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Kawaguchi, Tohru, Hidaka, Yasuhiro
• Granted Patent: US 7,081,960 B2
• Time in Patent Office: Days
• US Class Current: 356/492
• CPC Class Codes: G01B 2290/70 Using polarization in the interferometer
• CPC Class Codes: G01B 9/02018 Multipass interferometers, e.g. double-pass
• CPC Class Codes: G01B 9/02021 contacting different faces of object, e.g. opposite faces
• CPC Class Codes: G01B 9/02027 Two or more interferometric channels or interferometers
• CPC Class Codes: G01B 9/02061 Reduction or prevention of effects of tilts or misalignment

Abstract

A first polarizing beam splitter splits the light emitted by a light source into a measurement beam and a reference beam. The reference beam is returned by a second polarizing beam splitter and an optical member which is constituted by a right angle prism and a pentaprism, reenters the first polarizing beam splitter via a half wavelength plate and guided to a detector. On the other hand, the measurement beam is reflected by a corner mirror, is returned by the second polarizing beam splitter and the optical member, is reflected by the corner mirror again, reenters the first polarizing beam splitter via a half wavelength plate and guided to the detector. The optical member returns the measurement beam such that the measurement beam exits at the different point from the incident point and that light rays incident thereon in a state shifted from each other are returned with the shifted direction and shifted amount between each light rays kept unchanged.

Claims

1. An interferometer, comprising;

a light source;

a beam splitter; and

an optical member,

wherein the beam splitter splits the light emitted by the light source into a measurement beam and a reference beam,

wherein the reference beam is reflected by a fixed reflector;

wherein the measurement beam is reflected by a moving mirror, which includes at least two mutually orthogonal reflection planes;

further wherein the measurement beam reflected by the moving mirror are returned by the optical member, which returns the incident light such that the incident light exits at the point different from the incident point and that light rays incident thereon in a state shifted from each other are returned with the shifted direction and shifted amount between each light rays kept unchanged; and

still wherein the reference beam reflected by the fixed reflector and the measurement beam returned by the optical member via the moving mirror are detected.

2. The interferometer according to claim 1,

wherein the incident light is reflected odd number of times in the optical member before exiting therefrom.

3. The interferometer according to claim 2,

wherein the optical member comprises a pentaprism and a right angle prism.

4. The interferometer according to claim 3,

wherein the optical member functions as the fixed reflector.

5. The interferometer according to claim 1,

wherein the optical member functions as the fixed reflector.

6. The interferometer according to claim 1,

wherein the measurement beam forms double optical paths.

7. The interferometer according to claim 6,

wherein the optical member returns the incident light toward the moving mirror.

12. An exposure apparatus for transferring a pattern formed on a mask onto a substrate, comprising:

a first stage whereon the mask is placed;

a second stage whereon the substrate is placed; and

the interferometer according to claim 1,

wherein the moving mirror of the interferometer is disposed on at least one of the first stage and the second stage.

14. An exposure method for transferring a pattern formed on a mask onto a substrate, comprising:

a first step of measuring position of at least one of the mask and the substrate by using the interferometer according to claim 1;

a second step of illuminating the mask; and

a third step of transferring the pattern on the mask onto the substrate.

8. An interferometer, comprising:

a light source;

a beam splitter, which is disposed in the optical path of the light emitted by the light source and which splits the light into a measurement beam and a reference beam;

a fixed reflector, which is disposed in the optical path of the reference beam;

a moving mirror, which is disposed in the optical path of the measurement beam and includes at least two mutually orthogonal reflection planes; and

an optical member, which is disposed in the optical path of the measurement beam reflected by the moving mirror and which returns the measurement beam toward the moving mirror in a manner causing the incident measurement beam to be reflected odd number of times before exiting therefrom.

9. The interferometer according to claim 8,

wherein the optical member comprises a pentaprism and a right angle prism.

10. The interferometer according to claim 8,

wherein the optical member functions as the fixed reflector.

11. The interferometer according to claim 8,

wherein the measurement beam forms double optical paths.

13. An exposure apparatus for transferring a pattern formed on a mask onto a substrate, comprising:

a first stage whereon the mask is placed;

a second stage whereon the substrate is placed; and

the interferometer according to claim 8,

wherein the moving mirror of the interferometer is disposed on at least one of the first stage and the second stage.

15. An exposure method for transferring a pattern formed on a mask onto a substrate, comprising:

a first step of measuring position of at least one of the mask and the substrate by using the interferometer according to claim 8;

a second step of illuminating the mask; and

a third step of transferring the pattern on the mask onto the substrate.

16. An interference length measurement method, comprising:

a first step of splitting light emitted by a light source into a measurement beam and a reference beam;

a second step of causing the reference beam to be reflected by a fixed reflector;

a third step of causing the measurement beam to be reflected by a moving mirror that includes at least two mutually orthogonal reflection planes;

a forth step of returning the measurement beam having traveled via the moving mirror by an optical member; and

a fifth step of detecting the reference beam reflected by the fixed reflector and the measurement beam returned by the optical member via the moving mirror,

wherein, in the forth step, the measurement beam exits from the optical member at the point different from the incident point while the optical member keeping the shifted direction and shifted amount between the incident light rays, incident points of which are shifted from each other, unchanged.

17. The interference length measurement method according to claim 16,

wherein, in the forth step, the incident measurement beam is reflected odd number of times in the optical member before being emitted.

18. The interference length measurement method according to claim 16,

wherein, the second step comprises a step of causing the reference beam to be reflected by a corner mirror.

19. The interference length measurement method according to claim 18,

wherein, the second step comprises a step of causing the reference beam to travel via a pentaprism and a right angle prism.

20. The interference length measurement method according to claim 19,

wherein the reference beam travels via the pentaprism, the right angle prism and the fixed reflector;

and

wherein the measurement beam travels via the pentaprism, the right angle prism and the moving mirror.