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 +/- 0.1 eV) and postnitridation annealing (5.6 +/- 0.1 eV). 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.