Morphology investigations by atomic force microscopy of thin films and substrates for excimer laser mirrors

The surface microstructure of evaporated single layer and multilayer fluoride coatings for KrF lasers as well as the topography of uncoated fused silica substrates have been investigated with an atomic force microscope (AFM). The fluoride films exhibit a pronounced columnar microstructure that accounts for the typical surface morphology and causes surface roughness the magnetude of which depends on film thickness and substrate temperature. Well polished fused silica substrates show low surface roughness, which has been determined from both AFM and light scattering measurements.