Permeation barrier coatings by inductively coupled plasma CVD on polycarbonate substrates for flexible electronic applications

Silicon oxide (SiOx)/silicon nitride (SiNx) stacks and parylene thin films were deposited on flexible polycarbonate (PC) substrates using inductively coupled plasma chemical vapor deposition (ICPCVD) and a parylene reactor for permeation barrier applications. The effects of gas flow ratios on SiNx and SiOx film properties in terms of refractive index, internal stress, and water vapor transmission rate (WVTR) were investigated. It was found that the optical property and impermeability of SiNx and SiOx barrier films could be tailored by varying the gas flow ratio. The details of Ar plasma treatment effects on PC substrates in terms of contact angle, roughness, and WVTR were studied. The WVTR value of the optimum barrier structure (parylene + 3 pairs of SiOx/SiNx) could reduce to 4.74 × 10−5 g/m2/day after bending for 1000 times under a resistivity test (25 °C and 90% relative humidity). This result indicated that permeation barrier films prepared by ICPCVD could be a promising candidate for flexible electronic applications.

Research highlights
► SiOx/SiNx stacks are prepared by inductively coupled plasma chemical vapor deposition.
► The gas flow ratio affects the impermeability of barrier films.
► Ar plasma treatment improves the adherence of polycarbonate substrates.
► The optimal barrier structure is parylene with 3 pairs of SiOx/SiNx stack.