A Study of Low Temperature Atomic Layer Deposition Silicon Oxide for Thin Film Encapsulation

Abstract

Organic electronic devices have recently required a passivation layer that protects the active layers from oxygen and moisture. Thin film encapsulation (TFE) is most effective in preventing oxygen permeation and water vapor into the flexible devices. Plasma enhanced atomic layer deposition (PEALD) process, which provides growth characteristics that are similar to those of thermal ALD, enables a low temperature deposition by using O2 plasma instead of water (H2O) vapor. SiO2 has excellent properties, such as the large energy band gap (8.9 eV), low leakage current, impurity of low levels and low interface state density in the film. The required properties of SiO2 thin films are lower growth temperature, particle damage free process, excellent step coverage, and high throughput. PEALD offers a technique to regulate these problems. The PEALD method is a well known deposition based on self-limiting and sequential surface reactions, exhibiting saturation growth behavior and thickness control. In this study, we investigated the properties of SiO2 films on flexible PEN substrates deposited by PEALD encapsulation of OLEDs. As a result, the effects of deposition parameters on oxide film properties in terms of growth rate, refractive index, RMS roughness and water vapor transmittance rate (WVTR) will be discussed.