The Effects of Hillock Defect and Stress on the Moisture Resistance of Novel SiOxNy Passivation Layer for OLED Applications

• Main Authors: Yi-Jen Chen, 陳怡臻
• Other Authors: Jihperng (Jim) Leu
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/82653361131580608613

碩士 === 國立交通大學 === 材料科學與工程系所 === 96 === Organic light-emitting-diode displays (OLED) have gained momentum in the past few years because it was an emissive system creating its own light rather than relying on modulating a backlight. In addition, OLED possessed fast response time (<10ms, 100 times faster than TFT-LCD), wide view angle (>170°), true colors, excellent contrast ratio, brightness, low operating voltage and potentially less power consumption. However, its broad adoption has been hindered by the sensitivity of organic and electrode to the moisture and oxygen, which can quickly degrade the device performance if not properly protected. This motivated us to explore a simple, cheap, but reliable oxynitride-based thin film barrier for OLED in this study. The composition, microstructure and morphology of SiOxNy barrier layers deposited by a modified Ar ion beam evaporation system were first investigated. Then, the effects of substrate temperatures (60-90 oC) and gas flow rates (300-480 sccm) on the morphology and stress of SiOxNy/Al stack were examined. In addition, the roles of defects such as hillocks and grain sizes of Al films was studied and correlated with the moisture resistance of SiOxNy barrier films. Finally, the moisture barrier performance in terms of hillock density and hillock height was further discussed if multiple-layered passivation was warranted. In this study, SiOxNy layers were amorphous and the composition of Si: O: N was in the ratio of 1: 2: 0.67. Al films exhibited columnar structure with grain size distribution 50 to 100 nm after the deposition of SiOxNy. Al hillock was found to be the culprit of high moisture permeation in the passivation layer. A model of hillock formation in SiOxNy/Al was proposed in this thesis to illustrate the causes for their difference in hillock density and height. The hillock density was related to the initial Al grain size, while the hillock height was primarily derived by SiOxNy stress. The tallest height of hillock affected greatly on the numbers of barrier layers for complete sealing of defects. Therefore, high substrate temperature and high N2 gas flow rate deposition process yielded barrier films with less hillocks and improved moisture resistance if single layer of passivation was employed, while lower deposition temperature and low N2 gas flow rate were preferred for least number of layers if multiple-layer structure was adopted. In summary, defect control of Al hillocks was essential for controlling the moisture barrier performance in the practical OLED stack.