Stability and performance enhancement of a-IGZO TFTs by H incorporation

Abstract

We investigated the competing roles of hydrogen incorporation and oxygen vacancy (VO) passivation in amorphous In–Ga–Zn–O (a-IGZO) thin-film transistors by controlling the SiH4 flow rate during gate insulator deposition. While a low flow rate (130 sccm) yielded a superior field effect mobility (μFE) (15.0 cm2/V s) and positive bias temperature stability, a distinct turnover in the threshold voltage (VT) shift from negative to positive is observed under negative bias illumination stress. We propose a model to explain this anomalous transition: the initial negative shift arises from hole trapping and VO ionization, whereas the subsequent positive shift is driven by the transformation of donor-like peroxide states (O22−) into acceptor-like disorder states (O2−). X-ray photoelectron spectroscopy confirms that the magnitude of this instability correlates with the concentration of hydrogen-passivated oxygen vacancies ([VO]+[O–H]). These findings highlight the critical trade-off between defect passivation, hydrogen-induced doping, and bond weakening induced by excess hydrogen in a-IGZO devices.