Assessment of interface roughness during plasma etching through the use of real-time ellipsometry

Real-time in situ ellipsometry was used to investigate the etching of SiO2/silicon wafers with a high concentration of Cl2. We monitored the temporal trajectory of the ellipsometric parameter Δ and then selected several points for ex situ study using atomic force microscopy (AFM). There was a clearly observable transition period in the trajectory near the endpoint of the SiO2/Si interface. We studied the relationship between the ellipsometric parameter Δ and the same point in the AFM ex situ measurements. Three stages, thin film, the interface layer, and the substrate, were analyzed in this work.