Thermal stability of HfTaON films prepared by physical vapor deposition

We investigate the thermal stability of HfTaON films prepared by physical vapor deposition using high resolution transmission electronic microscope (HRTEM) and X-ray photoelectron spectroscopy (XPS). The results indicate that the magnetron-sputtered HfTaON films on Si substrate are not stable during the post-deposition an- nealing (PDA). HfTaON will react with Si and form the interfacial layer at the interface between HfTaON and Si substrate. Hf–N bonds are not stale at high temperature and easily replaced by oxygen,resulting in significant loss of nitrogen from the bulk film. SiO2 buffer layer introduction at the interface of HfTaON and Si substrate may effec- tively suppress their reaction and control the formation of thicker interfacial layer. But SiO2 is a low k gate dielectric and too thicker SiO2 buffer layer will increase the gate dielectric’s equivalent oxide thickness. SiON prepared by oxidation of N-implanted Si substrate has thinner physical thickness than SiO2 and is helpful to reduce the gate dielectric’s equivalent oxide thickness.