Characterization of Si-SiO2 interface traps in p-metal-oxide-semiconductor structures with thin oxides by conductance technique

Abstract

There has been a substantial effort made on the application of Nicollian–Goetzberger’s conductance technique to probe the Si-SiO2 interface traps on n-type substrates. However, it was reported that conductance measurement on the p-type substrate was impossible due to the strong surface potential fluctuations. By using metal-oxide-semiconductor (MOS) capacitors with thin (88–434 Å) oxides to damp out the fluctuations arising from the interface charge inhomogeneities, it is possible to carry out an accurate conductance measurement on as-oxidized p-MOS capacitors. A systematic dependence of the interface trap density on the oxide thickness and oxidation temperature is observed. The hole capture cross sections have no obvious dependence on the process conditions, but show an exponential dependence on the energy. Both the magnitude and bias dependence of the measured time-constant dispersion parameters are found to be much larger than those theoretically predicted. Results of numerical simulation show that the anomalous width of the conductance peaks observed for p-MOS structures is caused by the strong energy dependence of the hole capture cross sections, which has been overlooked in the conventional theory of MOS conductance.