An Optical Diffuse Reflectance Model for the Characterization of a Si Wafer with an Evaporated SiO₂ Layer

Thin films are a type of coating that have a very wide spectrum of applications. They may be used as single layers or composed in multilayer stacks, which significantly extend their applications. One of the most commonly used material for thin films is silicon dioxide, SiO₂. Although there are other tools that can be used to measure the thickness of SiO₂ films, these tools are very complex and sophisticated. In this article, we propose the use of an exponential two-layer light-material interaction model, throughout its diffuse reflectance spectra, as an alternative for the measurement of the thickness of evaporated SiO₂ on Si wafers. The proposed model is evaluated experimentally by means of a 980-nm-thick SiO₂ layer evaporated on a Si wafer. The results show that the proposed model has a strong correlation with the thickness measurements obtained using commercial equipment.