Transparent Barrier Coatings on High Temperature Resisting Polymer Substrates for Flexible Electronic Applications

Silicon nitride and parylene thin films were deposited onto flexible polyimide (PI) substrates using plasma-enhanced chemical vapor deposition and a parylene reactor for transparent barrier applications. The PI substrates from the Industry Technology Research Institute with high optical transmittance and high glass transition temperature were used. A relatively high growth temperature of was chosen to deposit the films. To characterize the films deposited under different growth temperatures, a wet-etching process was performed to visualize the defect distribution in the barrier films. After 120 min of etching, the etching area ratio decreased from 44.9 to 6.7%, while the average defect spacing increased from 125 to with increasing growth temperature. Under room temperature and relative humidity of 50%, four stacks with the films deposited at 80 and were demonstrated to decrease the water vapor transmission rate to and , respectively. As a result, ultralow permeation can be achieved with less repeating barrier stacks by using high temperature deposited films in the barrier structures.