Infrared optical constants and roughness factor functions determination: the HTHRTR method

This method was developed to determine the complex infrared optical constant of a single free-standing partially absorbing plate as wellas a thin solid film eposited on it. The method is based on exact formulas for normal transmittance T and near-normal reflectance R of the substrate as well as the film-substrate double layer. Coherent multiple reflections throughout the film and incoherent multiple reflections in the substrate as well as the intensity losses on the rough surface are taken into account. The influence of various data on the solution of the inverse problem is discussed by a contour map study. The method is explained using examples of both- and single-side-polished silicon wafers where the transmission and reflection roughness factor functions H(T),H(R) are determined for the rough surface. The thin-film example has been the silicon oxide film formed on the single-side-polished silicon substrate by chemical vapor deposition.