Transformation of interface states in silicon-on-insulator structures under annealing in hydrogen atmosphere

Changes induced by annealing the spectrum of states on a Si/SiO2 interface obtained by direct bonding and on a Si(substrate)/〈thermal SiO2〉 interface in silicon-on-insulator (SOI) structures were investigated by charge-related deep-level transient spectroscopy. The structures were formed by bonding silicon wafers and slicing one of the wafers along a plane weakened by hydrogen implantation. The SOI structures were annealed at 430°C for 15 min in hydrogen, which corresponded to the conventional mode of passivation of the Si/SiO2-interface states. The passivation of interface states by hydrogen was shown to take place for the Si/〈thermal SiO2〉 interface, as a result of which the density of traps substantially decreased, and the continuous spectrum of states was replaced by a band of states in the energy range Ec=0.1–0.35 eV within the entire band. For the traps on the bonded Si/SiO2 interface, the transformation of the centers occurs; namely, a shift of the energy-state band is observed from Ec=0.17–0.36 to 0.08–0.22 eV. The trapping cross section decreases by about an order of magnitude, and the density of traps observed increases slightly.