ERROR REDUCTIONS FOR A SERIOUS COMPENSATOR IMPERFECTION FOR NULL ELLIPSOMETRY

Error equations for angles of polarizers and analyzers are formulated for null ellipsometry with a seriously imperfect compensator. Analytic solutions of ellipsometric errors delta-psi and delta-DELTA for metallic samples show dependence on sin2(delta-tau/2)/cos delta-tau, where delta-tau is the retardation from a quarter-wave. The analytic solutions agree with results both from the direct computer simulation of null ellipsometry and from the numerical solutions for the error equations. Errors for data for a metallic sample agree with those predicted from the analytic solutions, and data after error reductions give accurate estimates for the complex refractive index and the surface roughness.