Single wavelength ellipsometry, although used extensively in the microelectronics field for the measurement of film thicknesses and refractive indexes, does not usually yield reliable refractive indexes for dielectric films less than 50 nm thick due to instrumental errors and software limitations. Addressing this issue, we employ previously developed ellipsometric procedures that enable a reliable assessment of refractive index profiles for a variety of thermally grown and chemically vapor deposited (CVD) dielectric films on Si substrates down to about 10 nm thickness, and we compare the results in terms of the current understanding about the film‐substrate interface. In all cases studied we find that the interfacial region is optically different than the bulk film and that the precise film processing can substantively alter the nature of the interface region.
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Chongsawangvirod et al. (1990) studied this question.