This method was developed to determine the complex infrared optical constant of a single free-standing partially absorbing plate as well as a thin solid film deposited on it. The method is based on exact formulas 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 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 HT,HR are determined for the rough surface. The thin-film example has been the silicon oxide formed on the single-side-polished silicon substrate by chemical vapor deposition.
© 1991 Optical Society of America
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