SiOxNy thin films were deposited by inductively coupled plasma enhanced chemical vapor deposition (ICP-PECVD) using hexamethyldisilazane (HMDS, 99.9%)/NH3/O-2/Ar at a low temperature, and examined for use as a water vapor diffusion barrier. The film characteristics were investigated as a function of the O-2:NH3 ratio. An increase in the O-2:NH3 ratio decreased the level of impurities such as -CHx, N-H in the film through a reaction with oxygen. Thereby, a more transparent and harder film was obtained. In addition, an increase in the O-2:NH3 ratio decreased the nitrogen content in the film resulting in a more SiO2-like SiOxNy film. Using SiOxNy fabricated with an O-2:NH3 ratio of 1:1, a multilayer thin film consisting of multiple layers of SiOxNy/parylene layers was formed on a polyethersulfone (PES, 200 gm) substrate, and its water vapor transmittance rate (WVTR) was investigated. A WVTR < 0.005 g/(m(2) day) applicable to organic thin film transistors or organic light emitting diodes was obtained using a multilayer composed of SiOxNy (260 nm)/parylene (< 1.2 mu m) on the PES. (c) 2006 Elsevier B.V. All rights reserved.