Abstract

Spectroscopic ellipsometry is a sensitive tool for the determination of thin film parameters and, in particular, for the investigation of thin film inhomogeneity. It was shown theoretically¹,² that the ellipsometric angle Ψ is most sensitive to the film inhomogeneity at the so-called half-wave (HW) wavelength points. The values of Ψ at the HW points can be used to determine the degree of inhomogeneity.¹,² These conclusions were obtained on the basis of the approximation that can be traced back to the early work by Schröder.³ Schroder’s approximation predicts essential properties of the ellipsometric angle Ψ but it is rather inaccurate with respect to the ellipsometric angle Δ. In particular, in this approximation the ellipsometric angle Δ is independent from the film inhomogeneity. At the same time ellipsometric experiments show that this is not true. Recently a new approximation was derived⁴ that allows for a more accurate study of the effects connected with the film inhomogeneity. In this paper we use this approximation to study the influence of the inhomogeneity on the ellipsometric angle Δ. The results of our theoretical study are applied to the investigation of structural properties of lanthanum fluoride films.

© 1998 Optical Society of America