Method for the protection of extreme ultraviolet lithography optics

Abstract

A coating for the protection of optical surfaces exposed to a high energy erosive plasma. A gas that can be decomposed by the high energy plasma, such as the xenon plasma used for extreme ultraviolet lithography (EUVL), is injected into the EUVL machine. The decomposition products coat the optical surfaces with a protective coating maintained at less than about 100 Å thick by periodic injections of the gas. Gases that can be used include hydrocarbon gases, particularly methane, PH3 and H2S. The use of PH3 and H2S is particularly advantageous since films of the plasma-induced decomposition products S and P cannot grow to greater than 10 Å thick in a vacuum atmosphere such as found in an EUVL machine.

Dependencies are inferred from the claim text.