A Two‐Step Annealing Treatment Method for InAlZnO Transistors Toward 3D Integration

A two‐step thermal annealing treatment strategy is proposed to enhance the electrical performance of the InAlZnO (IAZO) transistors, where the devices are initially pre‐annealing at 400 °C for 30 min, followed by a second annealing step across a wide temperature range of 200–500 °C. The optimized IAZO transistors exhibit excellent electrical properties, including a field‐effect mobility of 59.31 cm 2 V −1 s −1 , a subthreshold swing of 68.56 mV per decade, a turn‐on voltage of −0.74 V, an off‐state current below 100 pA, and an on‐to‐off current ratio over 10 7 . The devices show excellent bias stress stability and thermal stability as well. By Hall measurement, X‐ray photoelectron spectroscopy, and atomic force microscopy characterization analysis, it is found that two‐step annealing treatment stabilizes carrier concentration and smooths surface of the IAZO active layer. Furthermore, the inverters and 9‐stage ring oscillators based on the IAZO transistors are demonstrated. This work promotes the application of the oxide transistors in back‐end‐off‐line and monolithic 3D integration.