Optical system of a microlithographic projection exposure apparatus

摘要

An optical system of a microlithographic projection exposure apparatus contains a module, which can be fitted in the optical system and removed from it as a unit. The module contains a cavity which can be completely filled with a liquid and hermetically sealed, and a concavely curved optical surface which bounds the cavity at the top during operation of the projection exposure apparatus. This makes it possible to fill the module outside the optical system. The module can be tilted there so that no air bubble, which prevents complete filling, can form below the concavely curved optical surface.