Mirror unit and an exposure apparatus using the unit

摘要

A mirror unit includes a mirror having a reflecting surface, a holding member for supporting the mirror and an airtight chamber incorporating the mirror, supported by the holding member, in an airtight state. Either the mirror or the holding member constitutes a portion of a side wall of the airtight chamber. The mirror unit can be suitably used in an exposure apparatus which uses a synchrotron radiation light source or the like as a light source.