| 摘要 |
PROBLEM TO BE SOLVED: To prevent the outside air from entering a sealed container which hermetically contains an exposure optical system. SOLUTION: A wafer W is exposed to the light from an exposure light source 1 through an arranged optical system 2, lighting optical systems 3a to 3d, and the projection optical system 4. The optical system is put in the sealed container 14 which is filled with inert gas supplied from a gas supply device 16, and opening/closing valves 15a and 15b are arranged on its gas intake side and outlet side. A controller 19 controls them independently of control over the gas supply system and then, for example, when gas supply is stopped, the valves are automatically opened and closed to seal up the inert gas in the sealed container 14, thereby preventing outside air from entering it.
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