Patent Number: 
Section: claims

1. A laser produced plasma type extreme ultraviolet light source apparatus for generating extreme ultraviolet light by applying a laser beam to a target material, said apparatus comprising:a chamber in which extreme ultraviolet light is generated;a target supply unit configured to supply a target material to a predetermined position within said chamber;a laser beam focusing optics configured to focus a laser beam from a driver laser using a laser gas containing a carbon dioxide gas as a laser medium, for applying the laser beam to the target material supplied by said target supply unit to generate plasma;a collector mirror configured to collect the extreme ultraviolet light radiated from the plasma to output the extreme ultraviolet light; anda spectrum purity filter provided in an optical path of the extreme ultraviolet light from said collector mirror, and configured to transmit the extreme ultraviolet light and to reflect the laser beam, said spectrum purity filter including a wire grid polarizer having a pitch not larger than a half of a shortest wavelength of the laser beam from said driver laser. 2. The extreme ultraviolet light source apparatus according to claim 1, wherein said spectrum purity filter includes a mesh coated with a material having electrical conductivity on at least a surface thereof. 3. The extreme ultraviolet light source apparatus according to claim 2, wherein said mesh contains one of diamond, diamond-like carbon, silicon carbide, and silicon. 4. The extreme ultraviolet light source apparatus according to claim 2, wherein said material having electrical conductivity contains one of gold and molybdenum. 5. The extreme ultraviolet light source apparatus according to claim 1, wherein said spectrum purity filter includes a mesh coated with a material having electrical conductivity on at least a light incident surface thereof. 6. The extreme ultraviolet light source apparatus according to claim 5, wherein said mesh contains one of diamond, diamond-like carbon, silicon carbide, and silicon. 7. The extreme ultraviolet light source apparatus according to claim 5, wherein said material having electrical conductivity contains one of gold and molybdenum. 8. The extreme ultraviolet light source apparatus according to claim 1, wherein said spectrum purity filter includes a wire grid polarizer having a pitch not larger than substantially 5 μm. 9. The extreme ultraviolet light source apparatus according to claim 1, wherein said driver laser is configured to radiate a laser beam having linear polarization, and said wire grid polarizer is arranged such that an electric field vibration direction of the laser beam from said driver laser and an extending direction of wires are substantially the same. 10. The extreme ultraviolet light source apparatus according to claim 1, wherein said spectrum purity filter includes two wire grid polarizers each having a pitch not larger than substantially 5 μm and arranged orthogonal to each other. 11. The extreme ultraviolet light source apparatus according to claim 1, wherein said spectrum purity filter further includes a holder configured to hold a periphery of said wire grid polarizer such that a surface of said wire grid polarizer is flat. 12. The extreme ultraviolet light source apparatus according to claim 11, wherein said holder is formed with a channel configured to pass a medium for cooling or heating said wire grid polarizer. 13. The extreme ultraviolet light source apparatus according to claim 11, further comprising:a mechanism configured to rotate or vibrate said holder. 14. The extreme ultraviolet light source apparatus according to claim 1, wherein:said chamber is configured to introduce an etchant gas, andsaid etchant gas contains at least one selected from a hydrogen gas, a halogen gas, a hydrogen halide gas and an argon gas.