Environmental reliability and moisture barrier properties of silicon nitride and silicon oxide films using roll-to-roll plasma enhanced chemical vapor deposition

Abstract

The moisture barrier properties and long-term reliability of flexible thin barrier films under harsh environmental conditions are crucial parameters to consider for the real-world applications of flexible electronics. In this study, we fabricated flexible barrier films of single-layer silicon nitride (SiNx) and silicon oxide (SiOx) on a polyethylene terephthalate substrate using plasma enhanced chemical vapor deposition. We investigated the stability and degradation mechanism of SiNx and SiOx barrier films at high temperature and under high humidity using water vapor transmission rate (WVTR) measurements and cyclic bending tests. The changes in chemical composition, film density, surface roughness, and WVTR were analyzed after environmental reliability tests. It was found that high temperature and high humidity induced oxidation of the SiNx and SiOx films, resulting in an increase in the surface roughness and decrease in the film density. The SiOx film was oxidized faster than the SiNx film and formed large hillocks on the surface. The WVTR values of both films increased as the reliability test time increased, especially under environmental conditions of 85 °C/85% relative humidity, with the barrier performance of the SiOx film degrading more than the SiNx film. The SiNx film displayed stable barrier performance during 10,000 cycles bending test at a fixed bending radius of 10 mm, even after harsh environmental reliability tests.