Ellipsometric method for investigation of the optical anisotropy of thin films: theory and calculations

Ellipsometry is known to be a powerful and convenient tool for investigations of the optical properties of thin films. However, in investigations of thin anisotropic films its usage is not as wide as it could be, due to a limitation in resolving the components of the dielectric tensor in the case of the transverse optical anisotropy of thin films. This problem may be solved by the immersion technique, but immersion in its standard variant of changing the ambient medium may add new uncertainties to the system under investigation. The changing of reflecting properties of a substrate is proposed in this work for the investigation of such anisotropy. To avoid the ambiguity connected to different chemical properties of different substrates, it is convenient to use the substrates from the same material, but with different thicknesses of an oxide film. Such systems have different optical properties, at the same time possessing identical chemical ones. It is shown here that the usage of such structure gives sensitivity to the transverse optical anisotropy. Calculations of the sensitivity and precision of the determination of film parameters by means of the proposed method, as well as the modeling determination of anisotropic optical parameters of a thin film, are presented. (C) 1997 Elsevier Science S.A.