Deposition and permeation properties of SiNX/parylene multilayers on polymeric substrates

Silicon nitride (SiNX) deposited on flexible polycarbonate (PC) substrates by plasma-enhanced chemical vapor deposition have been investigated for thin-film barrier applications via the water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) measurements. A cyclic bending test was used to get quantitative information about the OTR and WVTR data of the single thin brittle SiNx/PC film with various thicknesses (50–400 nm). It was found that the SiNx/PC sample with a thickness of 100 nm possessed a minimum saturated crack density, as evidenced by the lowest OTR/WVTR values after the cyclic bending test. To improve the barrier performance, a smoothing, defect-decoupling organic film (parylene) was deposited on the top of the SiNx layer. The degradation after the cyclic bending test for the parylene/SiNx/PC structure was improved more than one order of magnitude as compared with that for the SiNx/PC sample. After 3000-times cyclic bending, the WVTR and OTR of the two pairs of parylene/SiNx coatings on PC can be maintained at a level near 0.01 g/m2/day and 0.1 cc/m2/day, respectively (below the detection limits of the MOCON systems). These indicate that the present multilayered coatings have high potential for future flexible display applications.