Patent ID: 8477285
Filing Date: 2013-07-02
Classification: B82Y,G03F,G21K

Abstract:
1. Optical assembly mounted in a projection exposure apparatus for extreme-ultraviolet lithography, comprising: at least one vacuum chamber; at least one optical element arranged in said vacuum chamber; said optical element having an optical surface arranged to be inpinged upon by a useful beam bundle Of the projection exposure apparatus; a pressure sensor configured to detect a gas pressure in said vacuum chamber which accommodates said optical element; a cleaning device arranged to clean said optical surface; said cleaning device being configured to perform particle cleaning of the optical surface at a gas pressure (p at least one access opening to the vacuum chamber lockable by a door or by a valve, with a door signal device which is configured to provide door a signal depending on a present position of the door, or with a valve signal device which is configured to provide a valve signal depending on a present position of the valve.