Verification of microwave annealing ambient effect on sol-gel-processed amorphous In-Ga-Zn-O thin-film transistors and application to inverter circuit

In this study, we conducted microwave annealing (MWA) on amorphous In-Ga-Zn-O (a-IGZO) thin films deposited by the sol-gel method, and then investigated the effects of ambient conditions on the electrical properties and reliability of a-IGZO thin-film transistors ( TFTs) and on the optical and chemical properties of a-IGZO thin films. On the other hand, pure N-2 ambient-treated TFTs exhibited the poorest transfer and output characteristics, but improved with increasing O-2 mixing ratio. In terms of stability, pure O-2 ambient-treated a-IGZO TFTs were excellent for both positive and negative gate bias stresses, but deteriorated with increasing N-2 mixing ratio. Also, static and dynamic tests of resistor-loaded inverters were carried out. As a result, the pure O-2 ambient-treated inverter showed excellent characteristics, while the pure N-2 ambient-treated inverter had poor characteristics. Meanwhile, pure O-2 ambient MWA has excellent carbon removal ability in sol-gel-processed a-IGZO films, lowering oxygen vacancies and impurities. Besides, it has an effect of increasing energy band gap, improving transmittance, increasing Fermi level and electron concentration, and contributing to improvement of mobility. Therefore, it was verified that MWA in pure O-2 ambient is very beneficial to improve the optical and chemical properties of the sol-gel-processed a-IGZO thin film and the electrical properties of TFTs.