Abstract

The ellipsometric function ρ of a film–substrate system is studied as the film thickness d is kept constant and the angle of incidence ϕ is changed. The generated constant-thickness contours (CTCs) are characterized by an introduced mathematical behavior indicator that represents a group of CTCs. The behavior of each group is developed and studied in the four planes $\varphi –d,X,Z\text{, and}\rho ,$where X is the film-thickness exponential function and Z is a previously introduced intermediate plane. In the $\varphi –d$ plane the film-thickness domain is identified and divided into a sequence of disconnected thickness subdomains (DTSs), depending on only $N_0\text{\hspace{0.17em}and}{N}_1\text{,}$ and their number depending on the range in which $N_0/N_1$ lies. The behavior of the CTCs in the successive planes X, Z, and ρ is then studied in each DTS, and the CTC's space is divided into disconnected subfamilies according to the behavior indicator. Equivalence classes that reduce the infinite number of subfamilies into a finite number are then introduced. The transformation from each plane to the next is studied with the origin of the Z plane mapped onto the point at ∞ of the ρ plane, forming a singularity. A multiple-film-thickness inequality is derived to determine the unique solution of the film thickness. The type of reflection being internal or external at both ambient–film and film–substrate interfaces affects the analysis and is also considered. To conclude we introduce the design of polarization-preserving devices and a novel oscillating single-element ellipsometer to fully characterize zero film–substrate systems as examples of applying the knowledge developed here.

© 2006 Optical Society of America

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