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

摘要

A method for the removal of a deposition on an optical element of an apparatus including the optical element includes providing an H 2 containing gas in at least part of the apparatus includes producing hydrogen radicals from H 2 from the H 2 containing gas; and bringing the optical element 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 element 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 methods can be applied in a lithographic apparatus.