Electronic structure and thermal stability of nitrided Hf silicate films using a direct N plasma

The thermal stability and electronic structure of nitrided xHf O2 (100-x) Si O2 (HfSiO) (x=30%, 55%, and 70%), prepared using a direct N plasma treatment, were investigated. N 1s spectra of nitrided Hf silicate films indicate that complex chemical states are generated. In particular, energy states with a high binding energy are stable, even after a postnitridation annealing. The quantity of N incorporated into the film is not dependent on the mole fraction of Hf O2 in the film, while the thermal stability of the N in the film is significantly influenced by the fraction of Hf O2 present. The thermal stability of the N in the film critically affects the composition and thickness of the film: i.e., after the postnitridation annealing, the thickness of the silicate film and the quantity of Hf and N are decreased, as the result of the dissociation of unstable Hf-N bonds.