Method for the protection of an optical element, device manufacturing method, apparatus including an optical element, and lithographic apparatus

摘要

A method for the removal of a deposition on an optical element of an apparatus including the optical clement includes producing hydrogen radicals from H 2 from an H 2 -containing gas and bringing the optical clement with deposition into contact with at least part of the hydrogen radicals and removing at least part of the deposition. Further, a method for the protection of an optical element of an apparatus including the optical clement includes providing a cap layer to the optical element by a deposition process and during or after use of the apparatus, removing at least part of the cap layer from the optical element in a removal process as described above. The hydrogen radicals are generated from H 2 from the H 2 containing gas by a filament, radiation, or a catalyst configured to convert H 2 into hydrogen radicals.