Synergistic Optimization of Stability in IGZO TFTs via Oxygen Flow Rate Regulation and Water Bath Treatment

The effects of water on oxide thin-film transistors (TFTs) are significant, yet complex, and remain inconclusive. In this work, the effects of water bath treatment on the performance of InGaZnO (IGZO) TFTs fabricated under different sputtering oxygen flow rates (0–7 sccm) were systematically investigated. The results reveal that the oxygen flow shows a large influence on the electrical properties, bias stress stability, and water-bathing stability. Especially, low and high flow rates correspond to large negative and positive bias-stress (NBS and PBS) threshold-voltage shifts (ΔVth), respectively. Oxygen vacancies (VO) that prefer gathering at the IGZO surface layers are the main reason for the large NBS ΔVth, while water bathing can gently etch the VO-rich layer, hence improving the NBS stability. As a result, the TFTs fabricated under a moderate oxygen flow rate (3 sccm) show a large field-effect mobility (30.1 cm2/V s), a threshold voltage close to 0 V (0.104 V), and small NBS/PBS ΔVth (−0.43 V/0.43 V) even after a 24 h water bath.