Surface assessment and mitigation of DUV optics

Abstract

CaF2 is one of the foremost optical materials used in ArF excimer laser optics. Surface quality of optically finished CaF2 plays an important role in the component’s lifetime. Several techniques were employed to assess surface quality of optically finished CaF2 in terms of top surface and subsurface damage, resulting in subsurface-damagefree CaF2. UV light and plasma interaction with CaF2 surfaces were investigated. The results were discussed in terms of surface roughness and cleanness associated with surface finishing and optical coatings.