Charge trapping and interface state generation by avalanche hot-electron injection in rapid thermal NH3 annealed and reoxidized SiO2 films

Abstract

In order to meet the needs of ultra large scale integration, SiO2 films are usually annealed prior to their use as the gate dielectric material in insulated gate field effect transistors (IGFETs). Using rapid thermal processing (RTP), SiO2 films with a thickness of 35 nm were annealed in NH3 and subsequently reoxidized. The properties of charge trapping and interface state generation of these films were investigated by an avalanche hot-electron injection technique. Experimental results indicate that by reoxidation, both the density of NH3 annealing induced traps and their capture cross section can be reduced; the hardness of the interface against hot-electron bombardment is improved while the low oxide fixed charge and interface state density as well as the high breakdown field are also preserved. An oxygen deficiency model can be used to explain the origin of these traps as well as the generation of interface states and the mechanism of reoxidation.