Effect of Simplified-Single-Step Microwave Annealing in O2 Ambient for High Performance Solution-Processed In–Ga–Zn–O Thin Film Transistors

In this study, we propose a simplified-single-step microwave annealing (S3-MWA) technique in an O2 ambient, which is a low thermal budget heat treatment method, for the application in solutionprocessed amorphous indium-gallium-zinc oxide (a-IGZO) thin films. For the application of solutionprocessed a-IGZO films in electronic devices, a multi-step post deposition annealing (PDA) process, which involves baking at low temperatures to vaporize the solvent, and high temperature conventional thermal annealing to remove defects in the film, is essential. To simplify the multi-step PDA process, we studied the possibility of reducing the thermal process temperature and time by replacing it with a single-step PDA process using microwave equipment. The electrical properties were compared to investigate the effect of the annealing method and ambient on solution-processed a-IGZO thin film transistors (TFTs). As a result, the S3-MWA-processed a-IGZO TFTs were found to exhibit superior electrical characteristics in comparison with the conventional PDA-processed devices. It was found that the O2 ambient process not only shortened the annealing time of S3-MWA but also improved the electrical properties. Furthermore, the S3-MWA was superior to the conventional PDA in the evaluation of device reliability under a gate bias stress test. The S3-MWA process in the O2 ambient was also responsible for improving the reliability of solution-processed a-IGZO TFTs. Therefore, we confirmed that the proposed S3-MWA in the O2 ambient is a more effective and promising technique than conventional PDA for the low thermal budget treatment of solution-processed a-IGZO TFTs.