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

Silicon nitride (SiNx) 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 200 degrees C was chosen to deposit the SiNx films. To characterize the SiNx 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 450 mu m with increasing growth temperature. Under room temperature and relative humidity of 50%, four SiNx/parylene stacks with the SiNx films deposited at 80 and 200 degrees C were demonstrated to decrease the water vapor transmission rate to 7.9x10(-4) and 7.41x10(-6) g/m(2)/day, respectively. As a result, ultralow permeation can be achieved with less repeating barrier stacks by using high temperature deposited SiNx films in the barrier structures.