EUV reflective ellipsometry in laboratory: determination of the optical constants and phase retarder properties of SiO2 at Hydrogen Lyman-Alpha

摘要

The optical properties of thick silicon dioxide on silicon substrate SiO2/Si were fully investigated at the hydrogen Lyman–alpha spectral line. In this case, it was observed that the reflectance measurements are not enough to determine reliablevalues of the optical constants, but a full polarimetric investigation is required. Thus, the optical constants were determinedtogether with the phase retarder properties by combining EUV reflective ellipsometry and reflectometry. The experimentalsystem used for the measurements is a reflectometer optimized for VUV–EUV spectral range and equipped with a linearrotating polarizer used as an analyzer. The results show the potential of the approach, suitable for cases in which thedetermination of the ellipsometric parameters, ratio ρ, and phase shift Φ, is required for a complete study of the optical andstructural properties of the samples. Moreover, it was found that SiO_2 behaves as a retarder by introducing a phasedifference between the s-and p- polarization components of the incoming light. The phase shift ranges from 18° to 160°depending on the incidence angle. The method, the experimental measurements, the analysis and the results are discussedthereafter.