Measurement of the thickness and refractive index of a thin film by analyzing reflected interference fringes

Abstract

We propose a novel, to the best of our knowledge, method to estimate the thickness and refractive index of a thin film by analyzing the reflectance as a function of the incidence angle. In most cases, interference fringes cannot be obtained from a film within a practical angular range unless it is much thicker than the wavelength. This problem was solved by adopting a high-index material as the medium of incidence, in which case several cycles of interference fringes were observed within a small range of incidence angles near the critical angle, allowing a fringe analysis. Consequently, the thicknesses, as well as the refractive indices of dielectric thin films, could be estimated. Our proposed method gave uncertainties of 20 nm and 0.0004 for the thickness and refractive index measurements, respectively.