Measuring small thickness changes of a thin film bywhite-light spectral interferometry

摘要

A white-light spectral interferometric technique is used for measuring small thickness changes of a Si02 thin filmgrown by thermal oxidation on a Si substrate. The technique is based on recording of the spectral interferogramsin a Michelson interferometer with one of its mirrors replaced by a thin-film structure. From the spectralinterferograms, the nonlinear-like phase function related to the phase change on reflection from the thin-filmstructure is retrieved. The phase function is fitted to the theoretical one to obtain the thin-film thicknessprecisely provided that the optical constants of the thin-film structure are known. This procedure is used formeasuring small thickness changes of a Si02 thin film attributed to different dopant concentrations of a Sisubstrate. The results of the technique are compared with those obtained by spectral reflectometry and verygood agreement is confirmed.