• DOI:10.12693/APhysPolA.140.215
• Corpus ID: 227746030

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

@article{Kanclivr2020PrecisionOS,
  title={Precision of Silicon Oxynitride Refractive-Index Profile Retrieval Using Optical Characterization},
  author={V'it Kancl'ivr and Jan V'aclav'ik and Karel vZ'idek},
  journal={Acta Physica Polonica A},
  year={2020}
}

• V'it Kancl'ivr, J. V'aclav'ik, Karel vZ'idek
• Published 8 December 2020
• Physics
• Acta Physica Polonica A

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