Surface Wave Plasma Oxidation at Low Temperature under Rare Gas Dilution

Abstract

Surface wave plasma oxidation was investigated under Kr gas dilution for the formation of the gate dielectric of poly-Si thin film transistors (TFTs). We clarified the plasma kinetics of plasma oxidation under rare gas dilution and the relationship between the oxidation rate and the plasma characteristics. It was also clarified that the oxygen atom in the surface wave plasma under Kr gas dilution is mainly generated by two processes: the electron impact dissociation of O2 gas and the quenching of Kr metastables through the reaction with O2 gas. The plasma kinetics under rare gas dilution for plasma oxidation can be explained as follows: The plasma highly diluted with rare gas generates high-density electrons and rare gas metastables, which efficiently generate high-density oxygen atoms from a small amount of O2 gas. Then the high-density oxygen atoms increase plasma oxidation rate. The structure and interface properties of the plasma-oxide films at 300°C are very similar to those of the thermal-oxide. At low temperatures, surface wave plasma oxidation is very effective especially under rare gas dilution.