Projection exposure apparatus

Abstract

A projection exposure apparatus for projecting a pattern image of an illuminated mask onto a substrate. The optical path can be divided into a plurality of hermetic blocks each having an inert gas sealed therein by a plurality of partition devices. According a one aspect of the invention, a hermetic sealing member is disposed in the space between the substrate-side of the projection optical system and the substrate for replacing the atmosphere existing in the optical path of the illuminating light in that space by a substance other than oxygen. According to another aspect of the invention, a plurality of independent chambers are formed in a frame. Lids, piping, and valves in the chambers are opened or closed in response to the value detected by oxygen density sensors.

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