Spectroscopic ellipsometry of inhomogeneous thin films exhibiting thickness non-uniformity and transition layers.

In this paper the complete optical characterization of an inhomogeneous polymer-like thin film of SiOCH exhibiting a thickness non-uniformity and transition layer at the boundary between the silicon substrate and this film is performed using variable angle spectroscopic ellipsometry. The Campi-Coriasso dispersion model was utilized for describing the spectral dependencies of the optical constants of the SiOCH thin film and transition layer. The multiple-beam interference model was used for expressing inhomogeneity of the SiOCH thin film. The thickness non-uniformity of this film was taken into account by means of the averaging of the elements of the Mueller matrix performed using the thickness distribution for the wedge-shaped non-uniformity. The spectral dependencies of the optical constants of the SiOCH thin film at the upper and lower boundaries together with the spectral dependencies of the optical constants of the transition layer were determined. Furthermore, the thickness values of the SiOCH film and transition layer, profiles of the optical constants of the SiOCH thin film and the rms value of local thicknesses corresponding to its thickness non-uniformity were determined. Thus, all the parameters characterizing this complicated film were determined without any auxiliary methods.