Comparison between Effects of PECVD-SiOx and Thermal ALD-AlOx Passivation Layers on Characteristics of Amorphous InGaZnO TFTs

We investigated the effects of the passivation layer on the characteristics of amorphous InGaZnO4 thin-film transistors (a-InGaZnO TFTs) by comparing AlOx film by thermal atomic layer deposition (TALD-AlOx) with SiOx film by plasma enhanced chemical vapor deposition (PECVD-SiOx). The PECVD-SiOx TFTs before and after final annealing exhibited conductive and hump characteristics, respectively. In contrast, both TALD-AlOx TFTs before and after final annealing exhibited enhancement characteristics. From secondary ion mass spectroscopy analysis, we found that TALD-AlOx effectively suppresses H injection into the underneath of the a-InGaZnO layer compared with PECVD-SiOx. We believe such suppression of H injection leads to the enhancement characteristics of TALD-AlOx TFTs. On the other hand, the conductive and hump characteristics of PECVD-SiOx TFTs may be attributed to a higher concentration of H injected into the a-InGaZnO layer and ion bombardment due to PECVD. From these results, we argue that plasma-free TALD-AlOx is effective for achieving good characteristics in a-InGaZnO TFTs. (C) The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.