Morphological observation of photo-densified PHPS under 172 nm VUV irradiation at varying light intensities for moisture barrier applications

An ultra-high moisture barrier silicon nitride (SiN X ) film was fabricated via solution-processed perhydropolysilazane (PHPS) under vacuum ultraviolet (VUV,172nm) irradiation, achieving outstanding barrier performance in 10 -5 g m -2 day -1 range. However, increasing the dose to 12J·cm -2 resulted in degraded barrier performance, which is considered to be caused by defects induced during densification process. In this study, surface analyses via coherence scanning interferometry (CSI) were discussed for revealing the structural changes. At 6J cm -2 under high-intensity irradiation, a higher number of larger and deeper pores (up to ~19υm in diameter) were observed compared to lower-intensity conditions (~13υm). However, at 12J cm -2 , pore size and count remained stable despite deteriorated barrier performance, indicating that micron-sized pores are not the primary cause. These results highlight the critical role of combining surface-sensitive techniques to resolve the origins of degradation and demonstrate the value of CSI in evaluating nanometer-scale morphology across millimeter-scale areas for solution-processed barrier films.