Hydrogen permeation through thin silicon oxide films

The time and temperature dependence of hydrogen permeation through silicon oxide into polycrystalline silicon was examined. The presence of an oxide layer causes the H flux into the underlying polycrystalline silicon (poly-Si) to decrease by more than 4 orders of magnitude compared to poly-Si without an oxide layer. For oxides thicker than 0.1 μm the H flux is independent of the hydrogenation time. On the other hand, a direct exposure of poly-Si to monatomic H exhibits a power-law decrease in H flux with time. Without the presence of an oxide layer the H flux exhibits a weak temperature dependence and is activated with ${\mathit{E}}_{\mathit{A}}$=0.31 eV. The activation energy does not change significantly when diffusing through an oxide, indicating that an increase in barrier height cannot account for the striking decrease in H flux. The implications of these results for H diffusion are discussed.