When an etchant for metal (e.g., HF) reaches an underlying silicon oxide layer, it may form silanol bonds or other hydrogen bonds that resist rinsing, so that some etchant remains to be trapped under the next deposited layer. Trapped etchant can create voids that eventually degrade the performance of the oxide layer. Exposing the surface to a liquid solution or gaseous precursor containing silane seals the defects without causing an overall thickness change. The silane reacts at sites with silanol (or other hydrogen) bonds, breaking the bonds and replacing the hydrogen with silicon, but does not react in the absence of a hydrogen bond.