High-k gate dielectric prepared by low-temperature wet oxidation of ultrathin metal nitride directly deposited on silicon

We investigated the electrical characteristics of metal oxynitrides such as TaOxNy and TiOxNy, which were simply prepared by low-temperature wet oxidation of TaN and TiN layers, respectively, for metal-oxide-semiconductor (MOS) gate dielectric applications. Compared with metal oxides, TaOxNy and TiOxNy showed excellent electrical characteristics such as low leakage current density, low capacitance equivalent oxide thickness and superior thermal stability. By X-ray photoelectron spectroscopy (XPS), we were able to confirm nitrogen incorporation in the oxide bulk and at the interface. The improvements of metal oxynitrides can be explained by both the naturally formed SiON underlayer and nitrogen incorporation, which can reduce the growth of the interfacial oxide layer and trap density.