Precision of Silicon Oxynitride Refractive-Index Profile Retrieval Using Optical Characterization

Layers with gradient refractive-index profile are an attractive alternative to conventional homogeneous stack coatings. However, the optical characterization and monitoring of graded is a complex issue, which has been typically solved by using simplified model mixed materials. Although this approach provides solution problem, precision, can be expected from refractive index gradient, remains unclear. In work, we study SiO_xN_y layers deposited via reactive dual ion beam sputtering. To characterize layers, use several methods including reflectance, transmittance spectra at broad range incident angles, together spectral ellipsometry. All data were simultaneously fitted general index. The used in our fit was based on varying stoichiometry. By altering profile, discussed sensitivity such alternation quality studied ambiguity merit-function minimization. We demonstrate that while scanning particular parameters seemingly very precise, obtain good agreement between experimental for shapes, where value major part differ as much 0.02 mean value.