Patent ID: 7495743
Filing Date: 2009-02-24
Classification: G03F

Abstract:
1. A method of forming an optical element of an immersion lithography system used to focus light from an optical source, the optical element having a face adapted to contact a liquid occupying a space between the face and an article to be patterned by the immersion lithography system, comprising: providing an optical element including a material degradable by the liquid at a surface of the optical element, the degradable material including a fluoride of an alkaline earth metal; and forming a protective coating covering the degradable material at the surface to protect the face of the optical element from the liquid, the protective coating being transparent to the light, stable when exposed to the light and stable when exposed to the liquid, said protective coating including an oxide of at least one metallic material selected from the group consisting of hafnium (Hf), silicon (Si), zirconium (Zr), aluminum (Al) and scandium (Sc) by supplying a source of oxygen and a vapor source of the metallic material to the surface of the optical element to successively form a plurality of monolayers of the oxide including a first monolayer of the plurality of monolayers in contact with the fluoride at the surface of the optical element.