Ellipsometry measurements on refractive index profiles of thin films

An ellipsometry technique for measuring the arbitrary refractive index profile of composite thin films is presented. The refractive index profile is obtained through a successive partitioning and computation process on measured data points with the aid of a φ₀/T plot, which reduces errors. Analyses of the required number of data points in the partitioned sections, the errors caused by the inappropriate partitioning, and the cumulative errors are performed. A Δφ₀/T plot is used to monitor the overall cumulative errors of the computation. Experimental examples using this technique to measure the refractive index profile of O-N-O and O-N composite thin films are included and results are compared with those obtained by Auger electron spectroscopy. It is shown that this method is sensitive enough to determine the refractive index profile to a resolution of 20 Å