High-Performance Transparent Barrier Films of SiO[sub x]∕SiN[sub x] Stacks on Flexible Polymer Substrates

Abstract

A transparent barrier structure consisting of silicon oxide (SiOx)∕siliconnitride(SiNx)(SiOx)∕siliconnitride(SiNx) stacks was deposited on a polycarbonate substrate at 80°C by plasma-enhanced chemical vapor deposition. Details of radio-frequency (rf) power effects on the SiOxSiOx and SiNxSiNx film properties in terms of etching rate, refractive index, internal stress, and water vapor transmission rate (WVTR) were investigated. It was found that the impermeability, flexibility, and optical property of the SiOx∕SiNxSiOx∕SiNx barrier films can be tailored by varying the rf power. A gradual decrease in the compressive internal stress of each stack film was designed to prevent the stress-induced cracks during the multilayer deposition process. The WVTR value of the optimum barrier structure ( SiNxSiNx + 6 pairs of SiOx∕SiNxSiOx∕SiNx ) can reduce to 3.12×10−6g∕m2∕day3.12×10−6g∕m2∕day under a calcium test (100 days at 25°C25°C , 40% relative humidity). After 5000 cyclic bending tests in a compressive mode, the WVTR value can keep below 3.54×10−5g∕m2∕day3.54×10−5g∕m2∕day . The performance of the SiOx∕SiNxSiOx∕SiNx barrier stacks presented has high potential for future flexible electronics applications.