Abstract

Coatings of uniform thickness distribution are required for many applications of thin films. Deposition from a point evaporation source onto a flat substrate will produce a nonuniform film because of distance and angle variations between the source and various points on the substrate. Several methods are commonly used to improve the thickness uniformity of thin film coatings. Examples are:¹ (a) an off axis position of evaporation source to a rotating substrate, (b) large area evaporation sources, (c) planetary rotation of the substrate, (d) simultaneous rotation and wobble of a substrate, and (e) rotating a tilted substrate. All methods except the last require vacuum chambers with a diameter considerably larger that that of the substrate and all require a deposition angle far from normal incidence. A non-normal deposition angle often produces film interfaces which are rougher than those obtained for near normal incidence. This roughness can drastically reduce the performance of a multilayer coating at short wavelengths.

© 1988 Optical Society of America