Optical arrangement i.e. extreme UV lithography system, has screen arranged in vacuum housing, and comprising guide surface for guiding trapped atomic hydrogen in direction of optical surface

摘要

The arrangement has a vacuum housing (2) in which an optical element (8) i.e. mirror, with an optical surface (8a) is arranged. A cleaning unit (18) adjusts cleaning-gas stream (19) on the optical surface, where the gas stream contains atomic hydrogen. A hydrogen trap arranged in the housing has a trapping surface for trapping atomic hydrogen not impinging on the optical surface. A screen is arranged in the housing, and comprises a guide surface for guiding the trapped atomic hydrogen in direction of the optical surface. An independent claim is also included for a method for cleaning an optical surface.