2162-8769/2013/2(1)/Q1/5/$28.00 © The Electrochemical Society Role of Oxygen in Amorphous In-Ga-Zn-O Thin Film Transistor for Ambient Stability

The role of oxygen in amorphous InGaZnO thin film transistor (a-IGZO TFT) is studied for the device ambient stability. The threshold voltage (Vth) value of 350◦C annealed a-IGZO TFT decreased apparently with the staying duration, and the average value shifted from 10.2 V to 5.8 V after a 9–day staying at the atmosphere. After raising the annealing temperature to 450◦C, the electrical stability issue was improved significantly with superior electrical parameters, including low threshold voltage (Vth), low subthreshold swing, high carrier mobility and a small Vth variation of ±0.5 V. It can be attributed to the enhancement of bonding energy of oxygen in the thermally-annealed a-IGZO film with the increase of thermal annealing temperatures. Besides, the stronger oxygen bonding could also suppress the absorption/desorption and UV-induced migration at the back surface, causing better electrical reliability and immunity against UV radiation, respectively. All these results showed the ambient stability is greatly related to the oxygen in a-IGZO film, and the desired electrical characteristic can be achieved via the optimization of thermal annealing process. © 2012 The Electrochemical Society. [DOI: 10.1149/2.012301jss] All rights reserved. Manuscript submitted April 18, 2012; revised manuscript received August 1, 2012. Published November 6, 2012. Transparent amorphous conductive oxide semiconductor (TAOS) has caught lots of attention for its superior transparent characteristics and electrical performance, even in amorphous crystallization phase.1 These advantages increase the possibility of future electronic appli