US Patent 10165664 Apparatus for decontaminating windows of an EUV source module

An apparatus, and a method of using the same, for monitoring and removing tin contamination on windows of an extreme ultraviolet lithography (EUVL) radiation source vessel includes an optical sensing module embedded in one or more monitoring units for inspecting the EUV radiation source. The optical sensing module measures intensity of infrared (IR) radiation. The apparatus further includes heating elements, hydrogen gas supply module, and a gas removal module for removing the tin contamination when the intensity of the IR radiation falls below a threshold of a baseline intensity corresponding to a substantially uncontaminated window.