Optical arrangement, particularly projection exposure system for extreme ultraviolet lithography, has optical element with reflective coating, which has cover layer, on whose surface oxidic impurities are present

摘要

The optical arrangement has an optical element (14) with a reflective coating, which has a cover layer, on whose surface oxidic impurities are present. A gas supplying unit (19) is provided for supplying a reducing gas to the surface. The material of the cover layer is selected from the group consisting of ruthenium, rhodium, palladium, platinum, iridium, niobium, vanadium, chromium, zinc or tin. The reducing gas contains a constituent, which is selected from the group comprising carbon monoxide and hydrogen, particularly activated hydrogen, or hydrogen-containing compounds. An independent claim is also included for a method for removing oxidic impurities from a surface of a cover layer of a reflective coating of an optical element.