Claims
- 1. An on-board spectrometer for a narrow bandwidth laser, comprising:
a scattering element capable of scattering a beam of laser light incident upon the scattering element; a high-finesse etalon positioned relative to the scattering element such that the etalon can create a fringe pattern from at least a portion of the scattered light beam; and a detection element capable of detecting an intensity of the fringe pattern in order to determine a spectral purity of the laser light.
- 2. An on-board spectrometer according to claim 1, wherein:
the detection element is capable of detecting an intensity of the fringe pattern in order to determine an E95 spectral purity of the laser light.
- 3. An on-board spectrometer according to claim 1, wherein:
the high-finesse etalon is a Fabry Perot etalon.
- 4. An on-board spectrometer according to claim 1, wherein:
the high-finesse etalon has a finesse of at least 40.
- 5. An on-board spectrometer according to claim 1, wherein:
the high-finesse etalon has a finesse of at least 20 and a free spectral range of less than about 10 pm.
- 6. An on-board spectrometer according to claim 1, wherein:
the detection element is a line scan camera.
- 7. An on-board spectrometer according to claim 1, wherein:
the on-board spectrometer is capable of monitoring a spectral purity of the laser beam over the entire operation time of the narrow bandwidth laser.
- 8. An on-board spectrometer according to claim 1, wherein:
the etalon consists of two parallel surfaces.
- 9. An on-board spectrometer according to claim 1, wherein:
the etalon includes a confocal set-up having curved surfaces.
- 10. An on-board spectrometer according to claim 1, wherein:
the etalon is sealed and is capable of having a controlled pressure therein.
- 11. An on-board spectrometer according to claim 1, wherein:
the etalon is thermally stabilized with an accuracy of better than ±2 K.
- 12. An on-board spectrometer according to claim 1, wherein:
the on-board spectrometer is further capable of monitoring the FWHM characteristics of the laser.
- 13. An on-board spectrometer according to claim 1, wherein:
the on-board spectrometer has a footprint allowing the spectrometer to be used as an on-line module within the laser.
- 14. An on-board spectrometer according to claim 1, further comprising:
a processing module capable of receiving intensity data from the detection element and calculating a spectral purity of the laser light.
- 15. An on-board spectrometer according to claim 1, further comprising:
a grating spectrometer capable of determining a spectral purity of the laser light, such that a bandwidth offset of the etalon can be determined by comparing a spectral purity value measured by the etalon.
- 16. An on-board spectrometer according to claim 1, further comprising:
at least one lens positioned to focus the laser light on the scattering element.
- 17. An on-board diagnostic module for determining the spectral purity of a narrow bandwidth laser, comprising:
a scattering element capable of scattering a beam of laser light incident upon the scattering element; a Fabry Perot etalon positioned relative to the scattering element such that the etalon can create a fringe pattern from at least a portion of the scattered light beam, the etalon having a finesse of at least 40; a line scan camera capable of detecting the intensity of each fringe in the fringe pattern; and a processor in communication with the line scan camera and capable of using information about the intensity to determine the spectral purity of the laser light.
- 18. An on-board diagnostic module according to claim 17, wherein:
the processor is capable of using information about the intensity to determine an E95 spectral purity of the laser light.
- 19. An on-board diagnostic module according to claim 17, wherein:
the processor is capable of subtracting an etalon offset from the intensity information in order to determine a spectral purity of the laser light.
- 20. A method for determining the spectral purity of a laser on-board, comprising:
scattering a beam of laser light emitted from a discharge chamber of the laser; creating a fringe pattern from the scattered laser light using a high finesse etalon; detecting the intensity of the fringe pattern using a high signal-to-noise detection element; and determining a spectral purity of the laser light using information about the intensity of the fringe pattern.
- 21. A method according to claim 20, wherein:
determining a spectral purity includes determining an E95 spectral purity.
- 22. A method according to claim 20, further comprising:
generating a beam of laser light in the discharge chamber.
- 23. A method according to claim 20, further comprising:
directing a portion of the beam of laser light to a scattering element in a diagnostic module of the laser.
- 24. A method according to claim 20, further comprising:
measuring an offset of the high finesse etalon using a grating spectrometer.
- 25. A method according to claim 24, wherein:
determining the spectral purity includes subtracting the offset from the intensity detected by the etalon.
- 26. A narrow bandwidth laser system, comprising:
a resonator including therein a discharge chamber filled with a gas mixture, the discharge chamber containing a pair of electrodes connected to a first discharge circuit for energizing the gas mixture and generating a laser beam in the resonator, the discharge chamber further including at least one window for sealing the discharge chamber and transmitting the laser beam; and a beam splitting element for redirecting a portion of the laser beam transmitted from the discharge chamber; and a diagnostic module positioned within the laser system to receive the redirected beam portion, the diagnostic module including therein: a scattering element capable of scattering the portion of the laser beam incident upon the scattering element; a high-finesse etalon positioned relative to the scattering element such that the etalon can create a fringe pattern from the scattered laser beam portion; and a detection element capable of detecting an intensity of the fringe pattern in order to determine a spectral purity of the laser beam.
- 27. An on-board spectrometer according to claim 26, wherein:
the detection element is capable of detecting an intensity of the fringe pattern in order to determine an E95 spectral purity of the laser light.
- 28. An on-board spectrometer according to claim 26, wherein:
the high-finesse etalon is a Fabry Perot etalon.
- 29. An on-board spectrometer according to claim 26, wherein:
the high-finesse etalon has a finesse of at least 40.
- 30. An on-board spectrometer according to claim 26, wherein:
the high-finesse etalon has a finesse of at least 20.
- 31. An on-board spectrometer according to claim 26, wherein:
the detection element is a line scan camera.
- 32. An on-board spectrometer for a narrow bandwidth laser, comprising:
a beam homogenizer capable of transmitting a beam of laser light incident upon the beam homogenizer, the beam homogenizer having a residual divergence of at least 20 mrad; a high-finesse etalon positioned relative to the beam homogenizer such that the etalon can create a fringe pattern from at least a portion of the transmitted light beam; and a detection element capable of detecting an intensity of the fringe pattern in order to determine a spectral purity of the laser light.
- 33. An on-board spectrometer according to claim 32, wherein:
the detection element is capable of detecting an intensity of the fringe pattern in order to determine an E95 spectral purity of the laser light.
- 34. An on-board spectrometer according to claim 32, wherein:
the high-finesse etalon is a Fabry Perot etalon.
- 35. An on-board spectrometer according to claim 32, wherein:
the high-finesse etalon has a finesse of at least 40.
- 36. An on-board spectrometer according to claim 32, wherein:
the high-finesse etalon has a finesse of at least 20 and a free spectral range of less than about 10 pm.
- 37. An on-board spectrometer according to claim 32, wherein:
the detection element is a line scan camera.
- 38. An on-board spectrometer according to claim 32, wherein:
the on-board spectrometer is further capable of monitoring the FWHM characteristics of the laser.
- 39. An on-board spectrometer according to claim 32, wherein:
the on-board spectrometer has a footprint allowing the spectrometer to be used as an on-line module within the laser.
- 40. An on-board spectrometer according to claim 32, further comprising:
a processing module capable of receiving intensity data from the detection element and calculating a spectral purity of the laser light.
- 41. An on-board spectrometer according to claim 32, further comprising:
a grating spectrometer capable of determining a spectral purity of the laser light, such that a bandwidth offset of the etalon can be determined by comparing a spectral purity value measured by the etalon.
CLAIM OF PRIORITY
[0001] This patent application claims priority to U.S. provisional patent application No. 60/434,044, entitled “Monitoring of spectral purity and advanced spectral characteristics of a narrow bandwidth excimer laser,” filed Dec. 16, 2002, which is hereby incorporated herein by reference.
[0002] The following applications are cross-referenced and hereby incorporated herein by reference:
[0003] U.S. patent application Ser. No. 10/293,906, entitled “HIGH-RESOLUTION CONFOCAL FABRY-PEROT INTERFEROMETER FOR ABSOLUTE SPECTRAL PARAMETER DETECTION OF EXCIMER LASER USED IN LITHOGRAPHY APPLICATIONS,” to Peter Lokai, filed Aug. 28, 2003; and
[0004] U.S. patent application Ser. No. 10/103,531, entitled “COMPACT HIGH RESOLUTION SPECTROMETER FOR LITHOGRAPHY LASERS,” to J. Kleinschmidt, filed Aug. 6, 2003.
Provisional Applications (1)
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Number |
Date |
Country |
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60434044 |
Dec 2002 |
US |