Numerous significant developments in the semiconductor industry have occurred over the past 70 years, particularly through the exploration and combination of various materials and their properties. Many innovative applications rely on the deposition and subsequent removal of monocrystalline materials on wafers. However, the reactive ion etching (RIE) process can lead to unwanted roughness, although sometimes roughness is desired for functional layers. Controlling roughness during material removal poses a challenge, making it essential to access roughness morphology information during processing. The higher pressure of RIE compared to most deposition techniques necessitates optical methods for monitoring surface conditions. Among these, reflectance anisotropy spectroscopy (RAS) is particularly effective. RAS can detect even minor changes in surface conditions during the growth and plasma etching of monocrystalline III/V semiconductors. It allows for in-situ, real-time monitoring of roughness evolution during RIE processes, utilizing statistical tools like principal component analysis (PCA) and linear discriminant analysis (LDA). This method facilitates the differentiation of various roughness morphologies and the identification of subtle differences within samples exhibiting a single roughness type.
