Long-Term Stability of SiNx Thin-Film Barriers Deposited by Low Temperature PECVD for OLED

摘要

Silicon nitride thin film barriers for organic light emitting diode with stress and water vapor transmission rate related to a function of NH3/SiH4 gas flow rate were deposited by plasma enhanced chemical vapor deposition at 85 degrees C. To evaluate the changes of the film properties before and after the storage in high temperature and humidity, the samples were stored in a chamber at 85 degrees C and 85% relative humidity for up to 240 hrs. Both the stress and the refractive index decreased with increasing NH3/SiH4 gas flow ratio. The values varied significantly with higher NH3/SiH4 gas flow ratios. The refractive index of the SiNx barrier with NH3/SiH4 ratio of 3.2 decreased to 1.44, which is a similar value to SiOx film. FTIR analysis showed that the Si-N and N-H bonds reacted with water vapor/oxygen and formed thermodynamically more stable Si-O or Si-OH bonds. The in-depth composition analysis by Auger electron spectorscopy showed that the oxidation rate for the NH3/SiH4 gas ratios of 0.8 and 3.2 were 0.88 and 6.63 angstrom/hr, respectively. Cross-section transmission electron microscopy confirmed the calculated oxidation rates of the SiNx barrier layers. (C) 2016 The Electrochemical Society. All rights reserved.