Electrical characterization of thin nanoscale SiOx layers grown on plasma hydrogenated silicon

Abstract

We analyzed the electrical characteristics of MOS structures with a SiOx layer grown on Si treated in plasma without heating. The hysteresis effect observed indicates the presence of traps spatially distributed into the oxide near the interface. The shift and the shape of the curves reveal a small oxide charge and low leakage currents, i.e. a high-quality dielectric layer. The generalized C-V curve was generated by applying the two-frequency methods on the C-V and G-V characteristics at frequencies in the range from 1 kHz to 300 kHz and by accounting for the series resistance and the leakage through the oxide layer. The energy spectra of the interface traps were calculated by comparing the experimental and the ideal theoretical C-V curves. The spectra showed the presence of interface traps with localized energy levels in the Si bandgap. These conclusions correlate well with the results on this oxide’s mechanical stress level, composition and Si-O ring structure, as well as on the interfacial region composition, obtained by our previous detailed multi-angle spectral ellipsometric studies. The ellipsometric data and the capacitance in strong accumulation of the C-V curves were used to calculate the thickness and the dielectric constants of the oxide layers.