Patent Number: 055725635
Section: claims

1. A mirror unit comprising: a mirror having a reflecting surface;  a holding member for supporting said mirror; and  an airtight chamber incorporating said mirror, supported by said holding member, in an airtight state,  wherein one of said mirror and said holding member constitutes a portion of a side wall of said airtight chamber and said mirror is detachably mounted to said airtight chamber through an opening in the side wall.  a radiation source for generating a radiation beam;  a mirror unit including a mirror for reflecting the radiation beam; and  an exposure unit for exposing a substrate with the reflected radiation beam,  wherein said mirror unit comprises:  a mirror having a reflecting surface;  a holding member for supporting said mirror; and  an airtight chamber incorporating said mirror, supported by said holding member, in an airtight state,  wherein one of said mirror and said holding member constitutes a portion of a side wall of said airtight chamber and said mirror is detachably mounted to said airtight chamber through an opening in the side wall. 2. A mirror unit according to claim 1, wherein said mirror comprises an X-ray mirror for reflecting X-rays. 3. A mirror unit according to claim 1, further comprising securing means for securing said mirror to said holding member. 4. A mirror unit according to claim 3, wherein said mirror secured to said holding member by said securing means comprises an integral member. 5. A mirror unit according to claim 4, further comprising means for mounting said integral member to said airtight chamber. 6. A mirror unit according to claim 5, further comprising a gasket provided between said integral member and said airtight chamber for assuring vacuum sealing of said airtight chamber. 7. A mirror unit according to claim 4, wherein said integral member further comprises means for cooling said airtight chamber. 8. An exposure apparatus comprising: 9. An exposure apparatus according to claim 8, further comprising securing means for securing said mirror to said holding member. 10. An exposure apparatus according to claim 9, wherein said mirror secured to said holding member by said securing means comprises an integral member. 11. An exposure apparatus according to claim 10, further comprising means for mounting said integral member to said airtight chamber. 12. An exposure apparatus according to claim 11, further comprising a gasket provided between said integral member and said airtight chamber for assuring vacuum sealing of said airtight chamber. 13. An exposure apparatus according to claim 10, wherein said integral member further comprises means for cooling said airtight chamber. 14. An exposure apparatus according to claim 8, wherein the substrate comprises a wafer, on which said exposure unit transfers a pattern by exposure. 15. An exposure apparatus according to claim 8, wherein said radiation source comprises a synchrotron orbit radiation apparatus for emitting a sheet-shaped radiation beam. 16. An exposure apparatus according to claim 15, wherein said mirror spreads the sheet-shaped radiation beam emitted from said synchrotron orbit radiation apparatus in a direction perpendicular to a sheet plane of the radiation beam.