HYDROGEN PERMEATION THROUGH THIN SILICON-OXIDE FILMS

The time and temperature dependence of hydrogen permeation through sil icon oxide into polycrystalline silicon was examined. The presence of an oxide layer causes the H flux into the underlying polycrystalline s ilicon (poly-Si) to decrease by more than 4 orders of magnitude compar ed to poly-Si without an oxide layer. For oxides thicker than 0.1 mu m the H flux is independent of the hydrogenation time. On the other han d, a direct exposure of poly-Si to monatomic H exhibits a power-law de crease in H flux with time. Without the presence of an oxide layer the H flux exhibits a weak temperature dependence and is activated with E (A) = 0.31 eV. The activation energy does not change significantly whe n diffusing through an oxide, indicating that an increase in barrier h eight cannot account for the striking decrease in H flux. The implicat ions of these results for H diffusion are discussed.