Patent Number: 
Section: claims

1. A laser produced plasma extreme ultraviolet (“EUV”) light source comprising:an EUV plasma production chamber having a chamber wall;a drive laser entrance window in the chamber wall;a drive laser entrance enclosure intermediate the entrance window and a plasma initiation site within the chamber and comprising an entrance enclosure distal end opening;at least one aperture plate intermediate the distal opening and the entrance window comprising at least one drive laser passage aperture. 2. The apparatus of claim 1 further comprising:the at least one aperture plate comprising at least two aperture plates comprising a first aperture plate and a second aperture plate defining an aperture plate interim space. 3. The apparatus of claim 1 further comprising;the at least one drive laser aperture passage comprising at least two drive laser aperture passages. 4. The apparatus of claim 2 further comprising:the at least one drive laser aperture passage comprising at least two drive laser aperture passages in each of the at least two aperture plates. 5. The apparatus of claim 1 further comprising:the laser passage aperture defining an opening large enough to let the drive laser beam pass without attenuation and small enough to substantially reduce debris passing through the laser passage aperture in the direction of the entrance window. 6. The apparatus of claim 2 further comprising:the laser passage aperture defining an opening large enough to let the drive laser beam pass without attenuation and small enough to substantially reduce debris passing through the laser passage aperture in the direction of the entrance window. 7. The apparatus of claim 3 further comprising:the laser passage aperture defining an opening large enough to let the drive laser beam pass without attenuation and small enough to substantially reduce debris passing through the laser passage aperture in the direction of the entrance window. 8. The apparatus of claim 4 further comprising:the laser passage aperture defining an opening large enough to let the drive laser beam pass without attenuation and small enough to substantially reduce debris passing through the laser passage aperture in the direction of the entrance window. 9. The apparatus of claim 2 further comprising:a purge gas within the aperture plate interim space at a pressure higher than the pressure within the chamber. 10. The apparatus of claim 4 further comprising:a purge gas within the aperture plate interim space at a pressure higher than the pressure within the chamber. 11. The apparatus of claim 6 further comprising:a purge gas within the aperture plate interim space at a pressure higher than the pressure within the chamber. 12. The apparatus of claim 8 further comprising:a purge gas within the aperture plate interim space at a pressure higher than the pressure within the chamber. 13. The apparatus of claim 5 further comprising:at least one laser beam focusing optic intermediate a source of the laser beam and the entrance window focusing a respective laser beam to the plasma initiation site within the chamber. 14. The apparatus of claim 6 further comprising:at least one laser beam focusing optic intermediate a source of the laser beam and the entrance window focusing a respective laser beam to the plasma initiation site within the chamber. 15. The apparatus of claim 7 further comprising:at least one laser beam focusing optic intermediate a source of the laser beam and the entrance window focusing a respective laser beam to the plasma initiation site within the chamber. 16. The apparatus of claim 8 further comprising:at least one laser beam focusing optic intermediate a source of the laser beam and the entrance window focusing a respective laser beam to the plasma initiation site within the chamber. 17. The apparatus of claim 9 further comprising:at least one laser beam focusing optic intermediate a source of the laser beam and the entrance window focusing a respective laser beam to the plasma initiation site within the chamber. 18. The apparatus of claim 10 further comprising:at least one laser beam focusing optic intermediate a source of the laser beam and the entrance window focusing a respective laser beam to the plasma initiation site within the chamber. 19. The apparatus of claim 11 further comprising:at least one laser beam focusing optic intermediate a source of the laser beam and the entrance window focusing a respective laser beam to the plasma initiation site within the chamber. 20. The apparatus of claim 12 further comprising:at least one laser beam focusing optic intermediate a source of the laser beam and the entrance window focusing a respective laser beam to the plasma initiation site within the chamber. 21. The apparatus of claim 13 further comprising:the at least one laser beam focusing element comprising at least two laser beam focusing optics intermediate a source of a respective one of at least two laser beams and the entrance window and each focusing the respective laser beam to a respective plasma initiation site within the chamber. 22. The apparatus of claim 14 further comprising:the at least one laser beam focusing element comprising at least two laser beam focusing optics intermediate a source of a respective one of at least two laser beams and the entrance window and each focusing the respective laser beam to a respective plasma initiation site within the chamber. 23. The apparatus of claim 15 further comprising:the at least one laser beam focusing element comprising at least two laser beam focusing optics intermediate a source of a respective one of at least two laser beams and the entrance window and each focusing the respective laser beam to a respective plasma initiation site within the chamber. 24. The apparatus of claim 16 further comprising:the at least one laser beam focusing element comprising at least two laser beam focusing optics intermediate a source of a respective one of at least two laser beams and the entrance window and each focusing the respective laser beam to a respective plasma initiation site within the chamber. 25. The apparatus of claim 17 further comprising:the at least one laser beam focusing element comprising at least two laser beam focusing optics intermediate a source of a respective one of at least two laser beams and the entrance window and each focusing the respective laser beam to a respective plasma initiation site within the chamber. 26. The apparatus of claim 18 further comprising:the at least one laser beam focusing element comprising at least two laser beam focusing optics intermediate a source of a respective one of at least two laser beams and the entrance window and each focusing the respective laser beam to a respective plasma initiation site within the chamber. 27. The apparatus of claim 19 further comprising:the at least one laser beam focusing element comprising at least two laser beam focusing optics intermediate a source of a respective one of at least two laser beams and the entrance window and each focusing the respective laser beam to a respective plasma initiation site within the chamber. 28. The apparatus of claim 20 further comprising:the at least one laser beam focusing element comprising at least two laser beam focusing optics intermediate a source of a respective one of at least two laser beams and the entrance window and each focusing the respective laser beam to a respective plasma initiation site within the chamber. 29. The apparatus of claim 21 further comprising:a respective focusing optic drive element for each of the at least two laser beam focusing optics. 30. The apparatus of claim 22 further comprising:a respective focusing optic drive element for each of the at least two laser beam focusing optics. 31. The apparatus of claim 23 further comprising:a respective focusing optic drive element for each of the at least two laser beam focusing optics. 32. The apparatus of claim 24 further comprising:a respective focusing optic drive element for each of the at least two laser beam focusing optics. 33. The apparatus of claim 25 further comprising:a respective focusing optic drive element for each of the at least two laser beam focusing optics. 34. The apparatus of claim 26 further comprising:a respective focusing optic drive element for each of the at least two laser beam focusing optics. 35. The apparatus of claim 27 further comprising:a respective focusing optic drive element for each of the at least two laser beam focusing optics. 36. The apparatus of claim 28 further comprising:a respective focusing optic drive element for each of the at least two laser beam focusing optics. 37. The apparatus of claim 29 further comprising:a purge gas supply providing purge gas to the aperture plate interim space and a purge gas discharge suction withdrawing purge gas from the aperture plate interim space. 38. The apparatus of claim 30 further comprising:a purge gas supply providing purge gas to the aperture plate interim space and a purge gas discharge suction withdrawing purge gas from the aperture plate interim space. 39. The apparatus of claim 31 further comprising:a purge gas supply providing purge gas to the aperture plate interim space and a purge gas discharge suction withdrawing purge gas from the aperture plate interim space. 40. The apparatus of claim 32 further comprising:a purge gas supply providing purge gas to the aperture plate interim space and a purge gas discharge suction withdrawing purge gas from the aperture plate interim space. 41. The apparatus of claim 33 further comprising:a purge gas supply providing purge gas to the aperture plate interim space and a purge gas discharge suction withdrawing purge gas from the aperture plate interim space. 42. The apparatus of claim 34 further comprising:a purge gas supply providing purge gas to the aperture plate interim space and a purge gas discharge suction withdrawing purge gas from the aperture plate interim space. 43. The apparatus of claim 35 further comprising:a purge gas supply providing purge gas to the aperture plate interim space and a purge gas discharge suction withdrawing purge gas from the aperture plate interim space. 44. The apparatus of claim 36 further comprising:a purge gas supply providing purge gas to the aperture plate interim space and a purge gas discharge suction withdrawing purge gas from the aperture plate interim space. 45. The apparatus of claim 37 further comprising:the entrance passage comprising a tapering enclosure wherein the distal end opening comprises an opening large enough to permit the at least one laser beam to pass without attenuation and small enough to substantially prevent debris from entering the entrance passage. 46. The apparatus of claim 38 further comprising:the entrance passage comprising a tapering enclosure wherein the distal end opening comprises an opening large enough to permit the at least one laser beam to pass without attenuation and small enough to substantially prevent debris from entering the entrance passage. 47. The apparatus of claim 39 further comprising:the entrance passage comprising a tapering enclosure wherein the distal end opening comprises an opening large enough to permit the at least one laser beam to pass without attenuation and small enough to substantially prevent debris from entering the entrance passage. 48. The apparatus of claim 40 further comprising:the entrance passage comprising a tapering enclosure wherein the distal end opening comprises an opening large enough to permit the at least one laser beam to pass without attenuation and small enough to substantially prevent debris from entering the entrance passage. 49. The apparatus of claim 41 further comprising:the entrance passage comprising a tapering enclosure wherein the distal end opening comprises an opening large enough to permit the at least one laser beam to pass without attenuation and small enough to substantially prevent debris from entering the entrance passage. 50. The apparatus of claim 42 further comprising:the entrance passage comprising a tapering enclosure wherein the distal end opening comprises an opening large enough to permit the at least one laser beam to pass without attenuation and small enough to substantially prevent debris from entering the entrance passage. 51. The apparatus of claim 43 further comprising:the entrance passage comprising a tapering enclosure wherein the distal end opening comprises an opening large enough to permit the at least one laser beam to pass without attenuation and small enough to substantially prevent debris from entering the entrance passage. 52. The apparatus of claim 44 further comprising:the entrance passage comprising a tapering enclosure wherein the distal end opening comprises an opening large enough to permit the at least one laser beam to pass without attenuation and small enough to substantially prevent debris from entering the entrance passage. 53. A laser produced plasma extreme ultraviolet (“EUV”) light source comprising:an EUV plasma production chamber having a chamber wall;a drive laser entrance window in the chamber wall;a drive laser entrance enclosure intermediate the entrance window and a plasma initiation site within the chamber and comprising an entrance enclosure distal end opening;a protective window intermediate the entrance enclosure and the entrance window. 54. The apparatus of claim 53 further comprising:the protective window comprising at least two protective windows selectively interposable intermediate the entrance enclosure and the entrance window. 55. The apparatus of claim 53 further comprising:an interposing mechanism selectively interposing one of the at least two protective windows intermediate the entrance enclosure and the entrance window. 56. The apparatus of claims 53 further comprising:a protective window cleaning zone into which at least one of the at least two protective windows is selectively positioned for cleaning when not interposed between the entrance enclosure and the entrance window. 57. The apparatus of claims 54 further comprising:a protective window cleaning zone into which at least one of the at least two protective windows is selectively positioned for cleaning when not interposed between the entrance enclosure and the entrance window. 58. The apparatus of claim 55 further comprising:a protective window cleaning mechanism cooperatively disposed in the cleaning zone. 59. The apparatus of claim 56 further comprising:a protective window cleaning mechanism cooperatively disposed in the cleaning zone. 60. The apparatus of claim 53 further comprising:a cleaning gas supply mechanism supplying cleaning gas to the cleaning zone. 61. The apparatus of claim 54 further comprising:a cleaning gas supply mechanism supplying cleaning gas to the cleaning zone. 62. The apparatus of claim 56 further comprising:a cleaning gas supply mechanism supplying cleaning gas to the cleaning zone. 63. The apparatus of claim 57 further comprising:a cleaning gas supply mechanism supplying cleaning gas to the cleaning zone. 64. The apparatus of claim 60 further comprising:a purge gas supply mechanism providing purge gas to a plenum intermediate the protective window and the entrance window. 65. The apparatus of claim 61 further comprising:a purge gas supply mechanism providing purge gas to a plenum intermediate the protective window and the entrance window. 66. The apparatus of claim 62 further comprising:a purge gas supply mechanism providing purge gas to a plenum intermediate the protective window and the entrance window. 67. The apparatus of claim 63 further comprising:a purge gas supply mechanism providing purge gas to a plenum intermediate the protective window and the entrance window. 68. The apparatus of claim 64 further comprising:the cleaning gas supply mechanism and the purge gas supply mechanism are the same gas supply mechanism. 69. The apparatus of claim 65 further comprising:the cleaning gas supply mechanism and the purge gas supply mechanism are the same gas supply mechanism. 70. The apparatus of claim 66 further comprising:the cleaning gas supply mechanism and the purge gas supply mechanism are the same gas supply mechanism. 71. The apparatus of claim 67 further comprising:the cleaning gas supply mechanism and the purge gas supply mechanism are the same gas supply mechanism.