Hydrogen and Oxygen Defect Engineering in Amorphous‐IGZO Thin‐Film Transistors by Rapid Thermal Annealing Ambient

The influence of rapid thermal annealing (RTA) ambients on defect formation and associated electrical characteristics, such as bias‐stress stability of bottom‐gated amorphous indium gallium zinc oxide (a‐IGZO) thin‐film transistors (TFTs) is investigated. Hydrogen incorporation in HfO 2 from thermal atomic layer deposition diffuses into the a‐IGZO channel during RTA, modulating defect states. Devices annealed in nitrogen (N 2 ) exhibit enhanced field‐effect mobility (∼6.75 cm 2 V −1 s −1 ), and near‐zero threshold voltage (∼0.46 V), due to hydrogen interstitials () acting as shallow donors. Annealing in oxygen (O 2 ) promotes oxygen interstitials () formation, leading to intermediate device performance. Under positive bias stress, O 2 ‐annealed and unannealed devices exhibit positive threshold voltage shifts (ΔV th ) of 0.42 and 0.48 V, respectively, originating from electron trapping at acceptor states, while N 2 ‐annealed TFTs exhibit a small negative ΔV th (−0.12 V), attributed to competing mechanisms between electron trapping at and electron emission from ionized . Negative bias stress induces negative ΔV th associated with oxygen vacancy () ionization, pronounced in N 2 ‐annealed devices owing to higher vacancy density. A defect‐state‐based band diagram is proposed to explain the observed electrical behavior in a‐IGZO/HfO 2 TFTs. These findings offer insight into defect modulation strategies for industrially important a‐IGZO transistor stability and performance.