Passivation of paramagnetic Si-SiO2 interface states with molecular hydrogen

Abstract

Dry thermal oxides were grown on (111) silicon substrates at 850 °C. The Pb centers associated with this (111) Si-SiO2 interface were observed with electron paramagnetic resonance to be stable under subsequent annealing in vacuum up to at least 850 °C. The rate of passivation of Pb centers with H2 was observed to be proportional to the concentration of H2 in the oxide and the density of Pb centers. The forward reaction rate constant kf is temperature dependent and obeys the Arrhenius relationship having an activation energy Ef of 1.66±0.06 eV and a pre-exponential factor k0f of 1.94 (+2./−1.)×10−6 cm3 /s for temperatures at least between 230 and 260 °C. The linear H2 pressure dependence in the rate of passivation and the magnitude of k0f are reasonably consistent with a model in which the H2 molecule reacts directly with Pb centers during its diffusional motion among the interstices of the SiO2 network and the reaction site at Pb centers.