CPC G03F 7/70866 (2013.01) [G03F 7/70925 (2013.01)] | 20 Claims |
1. An apparatus, comprising:
a vacuum chamber;
a reflective optical element arranged in the vacuum chamber, wherein the reflective optical element is configured to reflect an extreme ultra-violet (EUV) light; and
a cleaning module positioned in the vacuum chamber, wherein the cleaning module is operable to:
provide a mitigation gas flowing towards the reflective optical element, wherein the mitigation gas mitigates, by chemical reaction, contamination of the reflective optical element; and
provide a hydrogen-containing gas flowing towards the reflective optical element.
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