Electrical parameters of thin nanoscale SiO_x layers grown on plasma hydrogenated silicon

In the present paper results are presented on electrical characterization of the interface Si/SiO_x, formed by oxidation on Si wafers, previously exposed to rf hydrogen plasma. As a tool of investigations multiple frequency C-V and G-V measurements are applied. The data analysis was performed using two-frequency method to extract generalized frequency independent C-V characteristic. 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 SiO_x, 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 single layer system. From the data for the dielectric constant and refractive index suggestion is made that the grown oxides on hydrogenated Si contain voids thus reducing the dielectric constant. Correlation with oxide mechanical stress is found.