Sensitivity extrema in multiple-angle ellipsometry

A quantitative study of sensitivity of multiple-angle-of-incidence ellipsometry in determining several parameters of stratified structures is presented. The principles of determination of parameter errors caused by random and systematic errors in measured ellipsometric angles and by the use of incorrect values of fixed parameters are given. An appropriate choice of angles of incidence is discussed. The sensitivity for dielectric films on low-loss substrates is studied in detail, and large variations with the parameters, especially with film thickness-to-wavelength ratio, are observed.