Reflectance Difference Spectroscopy in Vacuum-Ultraviolet Range: Developing Measurement System and Applying to Characterization of SiO_2/Si Interfaces

摘要

Reflectance difference spectroscopy (RDS) in the vacuum-ultraviolet (VUV) range has been developed for the first time. The spectral range of RDS has been extended up to 8.4 eV by using a D_2 lamp, MgF_2-based optical elements, and an N_2-purged measurement environment. This new technique has been applied to investigate the oxidation-induced optical anisotropies of the Si surfaces with (110), (331), (120), and (113) orientations. The thermal oxidation of the Si(113) surface caused large changes in the RD spectrum, which we interpret as being due to anisotropic morphology at the SiO_2/Si interface. Distinct RD changes upon oxidation were also observed above 7 eV for the (110), (331), and (113) surfaces. We ascribe this feature to the optical transitions involving the electronic states of the interface Si-O bonds. These results demonstrate that VUV-RDS is a unique tool for characterizing dielectrics/semiconductor interfaces.