Abstract

It is possible to improve optical coating yields in existing vacuum chambers. Reflectance (or transmittance) monitor signals obtained in the deposition of low-index materials are substantially increased through utilization of multilayer witness techniques. Accuracy is enhanced by terminating layers in regions where signal changes are rapid with respect to optical thickness. In most applications, a highly interactive special purpose computer program based on Rouard’s method is utilized for translating thin-film designs into optical and crystal monitoring parameters. The program converts design optical thickness to physical thickness and reconverts to chamber optical thickness. Numerical and graphical output is expressed in terms familiar to coating technicians. There are a number of cases in which a more general program is utilized: absorbing films, high angles of incidence, and high number of layers where the nonmonochromaticity of the analyzing light must be taken into account. A color contour plot provides an over-view of monitor response vs wavelength. This program also includes ellipsometric output in optical monitor format: Psi and Delta plotted separately as a function of physical thickness.

© 1985 Optical Society of America