Effects of postnitridation annealing on band gap and band offsets of nitrided Hf-silicate films

Abstract

The effects of film composition and postnitridation annealing on band gap and valence band offset were examined in nitrided Hf-silicate films prepared using direct plasma nitridation. Regardless of the composition of Hf-silicate films, the band gap characteristics were similar after direct plasma nitridation (4.5±0.1eV) and postnitridation annealing (5.6±0.1eV). The decrease in band gap after direct plasma nitridation was caused by the formation of Si–N and Hf–N bonds, while the recovery of band gap by postnitridation annealing was influenced by the dissociation of unstable Hf–N bonds. The difference in valence band offset was strongly related to the chemical states of Si–N bonds.