Self-termination in the gas-phase layer-by-layer growth of an aza silane and water on planar silicon and nylon substrates

Abstract

The authors report the gas phase, layer-by-layer deposition of an organosilane (N-n-butyl-aza-2,2-dimethoxysilacyclopentane, 1) and either water or aqueous ammonium hydroxide onto two substrates: Si/SiO2 and nylon. This process results in smooth, water resistant, inorganic-organic barrier layers. The layer-by-layer deposition of 1 appears to be self-limiting to a few nanometers, which may make it useful where ultrathin films of controllable dimensions and uniformity are desired. The authors are unaware of another thin film system that has these properties. Films were characterized by spectroscopic ellipsometry, water contact angle goniometry, x-ray photoelectron spectroscopy, and atomic force microscopy. Interestingly, film thicknesses on nylon were much higher than on silicon, and films prepared in the presence of the ammonia “catalyst” were thinner than those prepared with water. Test circuits coated only with a fluorosilane showed higher penetration of water compared to those coated with a barrier layer of 1/H2O and the fluorosilane.