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Removal mechanisms in fine polishing calcium fluoride and silicon

: Klocke, Fritz; Dambon, Olaf; Schneider, Udo

Production Engineering. Research and development in Germany. Annals of the German Academic Society for Production Engineering 12 (2005), No.2, pp.5-10
ISSN: 0944-6524
Journal Article
Fraunhofer IPT ()

Monocrystals such as silicon (Si) or calcium fluoride (CaF2) are used as lens materials for optical systems using deep ultra-violet (DUV) wavelengths. One necessary condition for the efficiency of the optical systems is the generation of ultra-smooth surfaces in conjunctioun with minimum form deviation. For that purpose the lenses have to be finished by time-consuming multilevel polishing techniques. Therefore a systematic knowledge of the relevant mechanisms causing material removal and surface quality has to be built up. Fundamental investigations into the finish machining operations conducted on the monocrystalline materials silicon and calcium fluoride are presented in this paper. Apart from clarifying the removal mechanisms the study aims in particular to evaluate the significant influencing parameters and their interactions during the polishing process. This evaluation was based not on surface roughness and shape accuracy alone but also on the condition of the edge zone in terms of its chemical and mechanical characteristics.