Effects of water and hydrogen introduction during In–Ga–Zn–O sputtering on the performance of low-temperature processed thin-film transistors

Abstract

In–Ga–Zn–O (IGZO) films were deposited by sputtering in Ar + O2 + H2 and Ar + H2O atmosphere to investigate the effects of H2 and H2O introduction on physical and electrical properties of IGZO films and thin-film transistors (TFTs). A substantial reduction and oxidation of the IGZO films were confirmed by introducing H2 and H2O, respectively. We found that electron traps were formed for the Ar + H2O-sputtered IGZO TFTs, resulting in a degradation of field-effect mobility (μ FE), subthreshold swing (S.S.), and hysteresis (V H). In contrast, such degradations were not observed in the Ar + O2 + H2-sputtered IGZO TFTs and it exhibited μ FE of 12.5 cm2 V−1 s−1, S.S. of 0.15 V dec−1, and V H of 0.5 V. Hard X-ray photoelectron spectroscopy analysis revealed that excess oxygen incorporated during Ar + H2O sputtering is a possible cause of the TFT degradation. Thus, the reduction process, namely, Ar + O2 + H2 sputtering, is a promising approach for low-temperature-processed (∼150 °C) oxide TFTs for future flexible device applications.