Claims
- 1. An interferometer comprising:
a first polarizing beam splitter configured to direct an input beam in a direction that depends on a polarization state of the input beam; and a second polarizing beam splitter configured to receive an output beam from the first polarizing beam splitter and to direct the received output beam in a direction that depends on a polarization state thereof.
- 2. The interferometer of claim 1, further comprising a polarization rotator on an optical path between the first and second polarizing beam splitters for rotating the polarization of the output beam received from the first polarizing beam splitter.
- 3. The interferometer of claim 1, further comprising
a first retroreflector in optical communication with the first polarizing beam splitter; and a second retroreflector in optical communication with the second polarizing beam splitter.
- 4. The interferometer of claim 1, wherein the polarization rotator comprises a half-wave plate.
- 5. The interferometer of claim 1, further comprising a steering wedge disposed on an optical path between the first and second polarizing beam splitters.
- 6. The interferometer of claim 3, further comprising:
a first reflective polarization-rotator in optical communication with the first retroreflector; a second reflective polarization-rotator in optical communication with the second retroreflector.
- 7. The interferometer of claim 6, wherein at least one of the first and second reflective polarization-rotators comprises a mirror in optical communication with a quarter-wave plate.
- 8. A semiconductor lithography system comprising:
an interferometer as recited in claim 1; and a semiconductor lithography machine having
a base in optical communication with the second polarizing beam splitter of the interferometer, and a stage moveable relative to the base, the stage being in optical communication with the first polarizing beam splitter of the interferometer.
- 9. An interferometer comprising:
a first polarizing beam splitter in optical communication with a first retroreflector; a first reflective polarization-rotator on an optical path between the first polarizing beam-splitter and the first retroreflector; a second polarizing beam-splitter in optical communication with a second retroreflector; a second reflective polarization-rotator on an optical path between the second polarizing beam-splitter and the second retroreflector; and a third polarization rotator on an optical path between the first and second polarizing beam-splitters.
- 10. The interferometer of claim 9, wherein the first polarizing beam-splitter comprises:
a first beam-splitting plane oriented to reflect light having a first polarization toward the third polarization rotator, and a second beam-splitting plane in optical communication with the first beam-splitting plane, the second beam-splitting plane being
oriented to transmit light having a second polarization received from the first beam-splitting plane to the first retroreflector, and oriented to reflect light received from the first retroreflector and having the first polarization toward the third polarization rotator.
- 11. The interferometer of claim 9, wherein the second polarizing beam-splitter comprises
a mirror plane oriented to redirect light received from the first polarizing beam-splitter; and a third beam-splitting plane in optical communication
with the mirror plane, with the second retroreflector, and with the first polarizing beam-splitter, the third beam-splitting plane being
oriented to transmit light received from the mirror plane toward the second retroreflector, oriented to transmit, toward a detector, light received from the second retroreflector and having the first polarization, and oriented to transmit, toward the detector, light received from the first polarizing beam-splitter and having the second polarization.
- 12. The interferometer of claim 9, further comprising a steering wedge on the optical path between the first polarizing beam splitter and the second polarizing beam splitter.
- 13. The interferometer of claim 9, wherein the third polarization-rotator comprises a half-wave plate.
- 14. The interferometer of claim 9, wherein at least one of the first and second reflective polarization-rotators comprises a mirror in optical communication with a quarter-wave plate.
- 15. The interferometer of claim 9, wherein the first and second mirror are integral with each other.
- 16. A semiconductor lithography system comprising:
an interferometer as recited in claim 9; and a semiconductor lithography machine having
a base on which is mounted the second retroreflector; a stage on which is mounted the first retroreflector, the stage being moveable relative to the base;
- 17. An interferometer for receiving a measurement beam from a target location and a reference beam from a reference location separated from the target location by a separation distance, the interferometer comprising:
a reference path to be traversed by the reference beam within the interferometer the reference path having a reference-path length at least as long as the separation distance, and a measurement path to be traversed by the measurement beam within the interferometer, the measurement path having a measurement-path length at least as long as the separation distance.
- 18. The interferometer of claim 17, further comprising:
a first polarizing beam-splitter disposed to intersect the reference path and the measurement path; and a second polarizing beam splitter disposed to intersect the measurement path and the reference path.
- 19. The interferometer of claim 17, further comprising a polarization rotator disposed to intersect at least one of the reference path and the measurement path.
- 20 The interferometer of claim 19, wherein the polarization rotator comprises a reflective-polarization rotator.
- 21. The interferometer of claim 20, wherein the reflective polarization-rotator comprises a quarter-wave plate in optical communication with a mirror.
- 22. The interferometer of claim 18, further comprising a polarization rotator disposed to intersect the reference path and the measurement path between the first and second polarizing beam-splitters.
- 23. The interferometer of claim 22, wherein the polarization rotator comprises a half-wave plate.
- 24. A semiconductor lithography system comprising:
an interferometer as recited in claim 17; and a semiconductor lithography machine having
a base defining the reference location; a stage defining the target location, the stage being moveable relative to the base.
- 25. The semiconductor lithography system of claim 24, further comprising
a reference retroreflector mounted on the base at the reference location; and a measurement retroreflector mounted on the stage at the target location.
- 26. A method for determining the location of a moveable stage of a semiconductor lithography machine relative to a base separated from the stage by a separation distance, the method comprising:
directing a measurement beam along a measurement path that intersects the stage; directing a reference beam along a reference path that intersects the base; causing the reference beam to traverse a path length within an interferometer that is at least as long as the separation distance; and causing the measurement beam to traverse a path length within the interferometer that is at least as long as the separation distance.
RELATED APPLICATIONS
[0001] This application claims the benefit of the Apr. 24, 2002 priority date of U.S. provisional application No. 60/375,209, the contents of which are herein incorporated by reference.
Provisional Applications (1)
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Number |
Date |
Country |
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60375209 |
Apr 2002 |
US |