Moisture Diffusion in PECVD a-SiO_xN_y:H and a-SiO_x:H Coated on Polymer Resins: A Neutron Reflectometry Study

Abstract

The uptake of water of as-deposited thin films of SiO x N y and SiO x hard coatings on epoxy polymer resin by PECVD is studied by X-ray photoelectron spectroscopy (XPS) and ToF-SIMS. The absence of a chemical composition gradient at the dielectric-resin interface suggests a rough interface between the two materials. Upon storage in a cleanroom environment for 6 months (19 °C/40% RH), the uptake of water of the polymer resin layer was observed by XPS. Additionally, ToF-SIMS depth profiling revealed significant changes in the water content at the SiO x N yresin interface. We attribute these changes to the absorption of water diffusing through the dielectric-resin. Neutron reflectometry performed under a dry and D 2 O atmosphere confirms that D 2 O was nonreversibly absorbed in the SiO x N y -resin, but only limited moisture diffusion was observed in the SiO x -resin.