DIPOLES IN SiO_2: BORDER TRAPS OR NOT?

摘要

Two types of dipoles are observed in thermal SiO_2 gate oxides of metal-oxide semiconductor (MOS) devices exposed to ionizing radiation or high-field electrical stress. The first defect is responsible for much of the reversibility of trapped-hole "annealing," capacitance-voltage hysteresis, and 1/f noise in MOS devices, especially for oxides with high O vacancy densities. Recent theoretical calculations confirm this dipole is associated with the E'_γ defect, as suggested initially by Lelis and co-workers. A second type of dipole shows a different annealing response in thermally stimulated current (TSC) measurements. On the basis of density functional theory calculations, and consistent with the TSC and radiation effects and reliability literature, we suggest that this defect may be a dipole consisting of trapped positive charge near a hydrogen atom passivating a dangling Si bond at or near the Si/SiO_2 interface. Implications are discussed for models of MOS radiation response and long-term reliability.