Interface characterization of nanoscale SiOx layers grown on RF plasma hydrogenated silicon

In the present paper, results are presented on electrical characterization of the interface Si/SiOx, formed by oxidation on Si wafers previously exposed to rf hydrogen plasma. As tools of investigations, multiple frequency C-V and G-V measurements were applied. The data analysis was performed using a two-frequency method to extract a generalized frequency independent C-V characteristic. The interface trap densities were evaluated from the generalized C-V data by comparison with theoretical data for an ideal interface. A set of localized states, acting as interface traps, was found that characterize the interface of Si to substoichiometric SiOx, layer with x< 2. The dielectric constant of the oxides was calculated from the capacitance in accumulation of the generalized C-V curves. The thickness and the refractive index of the oxide layers were obtained from ellipsometric data analysis assuming the oxide-Si substrate as being a single layer system. From the data for the dielectric constant and refractive index, the suggestion is made that the oxides grown on hydrogenated Si contain voids thus reducing the dielectric constant. Correlation with oxide mechanical stress is found.