Defect generation under substrate-hot-electron injection into ultrathin silicon dioxide layers

Point-defect generation in ultrathin silicon dioxide layers is studied for various initial hot-electron distributions at the cathode/oxide interface using injection modes dependent on the device structure. Consistent with thicker gate oxides studies, these experiments show unequivocally that defect buildup leading to destructive breakdown depends on electron energy, not oxide electric field (or inverse field). Bulk oxide electron-trap generation is shown to depend on the energy delivered to the anode by the hot electrons transported through the oxide layer after injection from the cathode contact. However, defect generation near the cathode/oxide interface is shown to also depend on the energy of the hot electrons delivered to this interface from the silicon bulk, particularly for nonthermal distributions. By comparing bulk oxide-defect generation due to substrate-hot-electron injection to that due to thermal Fowler-Nordheim injection, direct information about the electron energy distribution at the cathode/oxide interface is obtained for any biasing configuration. The implications of these studies on the reliability of actual device operation where channel-hot-electron effects may occur are discussed. (C) 1999 American Institute of Physics. [S0021-8979(99)00416-8].