Application of UV-VIS and FTIR spectroscopic ellipsometry to the characterization of wet-chemically treated Si surfaces

In this paper, investigations of roughness, oxide and hydrogen coverage of Si(111) surfaces after various wet-chemical treatments using spectroscopic ellipsometry (SE) both in the ultraviolet/visible (UV-VIS) and in the infrared (IR) spectroscopic region are reported. FTIR SE measurements yielded detailed information on the Si-H bonds on the surface of H-terminated Si(111) wafers. The characteristic structure in the IR ellipsometric spectra at 2083 cm(-1) can be modeled by an anisotropic oscillator. A correlation is established between the morphological structure of the cleaned Si surface caused by chemical preparation and the resulting electronic surface properties monitored by additional surface photovoltage (SPV) measurements. The results of these systematic investigations have been successfully used for optimization of wet-chemical preparation methods aimed at atomically flat H-terminated Si(111) surfaces with very low surface state densities. Additionally, native oxide growth on initially H-terminated Si(111) was correlated to the evolution of rechargeable interface states determined by SPV measurements.