Morphology and water-barrier properties of silane films on aluminum and silicon

The goal of this study is to understand the effect of the substrate on the morphology and water-barrier properties of bis-silane films. Silane films are deposited on both Si and Al. Neutron reflectivity is used to assess the effect of hydrothermal conditioning on the films. Aluminum on silicon (no silane) was characterized first to facilitate understanding of the more complicated silane on Al-coated Si. A 200-Å Al layer with 55-Å oxide covers the surface of the silicon wafer. The reflectivity data show that water penetrates into the oxide layer. Silane films deposited on either Al or Si substrates have similar bulk and top-surface morphology. Studies of silanes on Si wafers, therefore, can be generalized to include Al. The substrate–silane interface, however, does depend on both the substrate and the silane. Because pH of the bis-sulfur silane solution is outside of the stability range for Al2O3, dissolution of the thin oxide film occurs during solution deposition. A water-depletion area is formed at the interface region due to this reaction.