Hot-electron trapping in thin LPCVD SiO2dielectrics

The electron-trapping and surface-state generation characteristics of thin LPCVD SiO2dielectrics have been studied using avalanche hot-electron injection. Layered structures of thermal and LPCVD oxide have been examined as a function of anneal time and temperature. After a 1000°C anneal, bulk trapping in the LPCVD oxide was reduced to levels comparable to those in a high-quality dry thermal oxide. Sensitivity to remaining traps was reduced by the presence of a thermal oxide layer on the semiconductor surface. After a post-deposition anneal (PDA), these layered surfaces demonstrated hot-electron performance equal to that of thermal oxide within measurable limits. Also, layered structures generally demonstrated better resistance to surface-state generation than thermal oxides alone. Since less chlorine is incorporated into the layered structures during fabrication, this result is consistent with a recent model identifying broken chlorine bonds as the origin of surface states.