Variable-angle spectroscopic ellipsometry of considerably non-uniform thin films

A theoretical approach for including considerable thickness non-uniformity of thin films into the formulae employed within variable-angle spectroscopic ellipsometry is presented. It is based on a combination of the efficient formulae derived for the thickness distribution density corresponding to a wedge-shaped non-uniformity with dependences of the mean thickness and root mean square (rms) of thickness differences on the angle of incidence that take into account the real non-uniformity of the shape. These dependences are derived using momentum expansion of the thickness distribution density. The derived formulae are tested by means of numerical analysis. An application of this approach is illustrated using the optical characterization of a selected sample of non-uniform SiO(x)C(y)H(z) thin films using phase-modulated ellipsometry.