PLASMA ION-ASSISTED EVAPORATIVE DEPOSITION OF SURFACE LAYERS

Abstract

Vacuum thin film processes are becoming increasingly important in modern high technology because of their possible use in changing the surface properties over a wide range while maintaining the properties of the bulk material. The requirements for temperature stability and low absorption and scattering losses are becoming ever more stringent for thin films used in optical applications. Furthermore, synthetic substrate materials are more and more used for ophthalmic lenses as well as for high precision optical components. Especially important is the fact that a rather soft substrate material can be covered with a hard surface layer, thus providing a high scratch-resistance without the brittleness of common hard materials. In principle, the process technology for vacuum deposition of thin films can be subdivided in physical vapor deposition (PVD) (evaporation, sputtering) and chemical vapor deposition (CVD) with subgroups thermal CVD, PECVD, and photo CVD. Evaporation, the classical method of producing thin coating layers, using the technique of electron beam evaporation provides a comparatively high rate of deposition. The coating of sha,ped or two-dimensional optical substr+ites also uses evaporation for reasons of better film distribiItion. Evaporation processes under vacuum require an arrangement of an evap­ oration source and the substrate to be covered such that the evaporated