Moisture barrier enhancement by spontaneous formation of silicon oxide interlayers in hot wire chemical vapor deposition of silicon nitride on poly(glycidyl methacrylate)

Abstract

We deposited a silicon nitride (SiNx)–polymer hybrid multilayer moisture barrier in a hot wire chemical vapor deposition (HWCVD) process, entirely below 100 °C. The polymer, poly(glycidyl methacrylate) (PGMA), was deposited by initiated chemical vapour deposition and the SiNx in a dedicated HWCVD reactor. Line profile investigation of our barrier structures by cross-sectional scanning transmission electron microscopy and energy dispersive X-ray spectrometry reveals that, upon deposition of SiNx on top of our polymer layer, an intermediate layer of silicon oxide (SiOx) like material is formed. X-ray photoelectron spectroscopy measurements confirm the presence of this material and indicate the epoxy rings in the PGMA material open upon heating (to 100 °C) and exposure to atomic hydrogen and amine species in the HWCVD process. The oxygen atoms subsequently react with silicon and nitrogen containing radicals to form SiOxNy. The interlayer turns out to be highly beneficial for interlayer adhesion and this is considered to be one of the reasons for the excellent barrier properties of our multilayer.