Optical characterization of inhomogeneous thin films of ZrO2 by spectroscopic ellipsometry and spectroscopic reflectometry

Abstract

In this paper results concerning the optical characterization of inhomogeneous thin films of ZrO2 are presented. The optical characterization of these films is performed using the simultaneous interpretation of experimental data corresponding to variable angle of incidence spectroscopic ellipsometry (VASE) and near-normal incidence spectroscopic reflectometry (NNSR). It is shown that the ZrO2 films exhibit a depth inhomogeneity concerning their refractive indices. Further, it is shown that the ZrO2 films studied can be replaced by the four-layer system from the point of view of satisfactory fits of the experimental data. The values of the thicknesses and spectral dependences of the refractive indices of these four films are determined. Moreover, it is proved that the individual methods, i.e. VASE and especially NNSR, cannot be used separately to characterize the ZrO2 films investigated. The simultaneous treatment of the spectral dependences of the ellipsometric parameters and the reflectance measured for different angles of incidence allows complete optical characterization of these inhomogeneous films to be performed, i.e. only a combination of VASE and NNSR enables us to determine the values of both the refractive indices and the thicknesses of the films replacing the inhomogeneous ZrO2 films investigated from the optical point of view. Copyright © 2000 John Wiley & Sons, Ltd.