Enhancing analysis efficiency: Automation of spectroscopic ellipsometry for crystalline semiconductors and transparent conductive oxides

Abstract

One significant drawback of a spectroscopic ellipsometry (SE) technique is its time-consuming and often complicated analysis procedure necessary to assess the optical functions of thin-film and bulk samples. Here, to solve this inherent problem of a traditional SE method, we present a general way that allows complete automation of SE analyses for crystalline-phase semiconductors and transparent conductive oxides (TCOs), exhibiting complex absorption features. In particular, we have modified a scheme established in our previous study, which performs a non-linear SE fitting analysis only in a low energy region at the beginning, while the analyzed energy region is gradually expanded toward higher energy by incorporating additional optical transition peaks. In this study, we have further developed a unique analyzing-energy search algorithm, in which a proper analyzing-energy region is determined to incorporate the feature of a new transition peak. The proposed method (ΔM method) has been applied to analyze perovskite-based crystalline samples, including hybrid perovskite (CH3NH3PbI3), chalcogenide perovskites (SrHfS3 and BaZrS3), and TCOs (In2O3:W, In2O3:Sn, and ZnO:Ga). In the automated analyses of the crystalline semiconductors, 7 ∼ 8 transition peaks are introduced automatically to describe sample dielectric functions, while structural parameters, such as thin-film and roughness thicknesses, are also determined simultaneously. It is, however, found that, in the crystalline semiconductor analyses, the slight correction for the surface roughness layer thickness is necessary to remove the artifact generated in the automated analyses. We have further confirmed that the developed method is superior to a B-spline semiautomatic-analysis method, which has been adopted in earlier studies. The established method can drastically reduce an analysis time and expands the application area of spectroscopic ellipsometry considerably.