On the behavior of deuterium in ultrathin SiO2 films upon thermal annealing

Following the observation of the large isotopic effect in D(2) passivated gate dielectrics [J. Lyding, K. Hess, and I. C. Kizilyalli, Appl. Phys. Lett, 68, 2526 (1996)], we studied the behavior of deuterium in ultrathin SiO(2) films by nuclear reaction analysis techniques, Accurate concentrations of deuterium in the films, deuterium depth distributions, and deuterium removal from the film upon thermal annealing in vacuum have been examined. For D(2) passivated films, we found rather high concentrations of deuterium near the SiO(2)/Si interface, well above both the solubility of deuterium in silica and the maximum concentration of electrically active defects at the interface. Our results suggest a complex multistep mechanism of thermally activated deuterium removal from the film, which probably consists of D detrapping, diffusion, and desorption steps. (C) 1998 American Institute of Physics.