Fully Sputtered a‐IGZO TFTs with Ultrathin Al₂O₃ Passivation and Low‐Thermal‐Budget Annealing for Enhanced Logic Circuit Performance

Developing low‐temperature sputtering for gate dielectrics is crucial for simple, flexible oxide TFT fabrication. However, such films suffer from low capacitance, high leakage, and high interfacial defects. This work proposes a synergistic strategy using an ultrathin alumina passivation layer combined with ultraviolet‐assisted oxygen ambient rapid thermal annealing (UV‐ORTA) to enable fully low‐temperature sputtered high‐performance amorphous indium gallium zinc oxide (a‐IGZO) TFTs. The UV‐ORTA process significantly improves the gate dielectric by reducing oxygen vacancies, increasing optical bandgap, and boosting capacitance density. The sputtered alumina layer effectively optimizes the dielectric/active layer interface, reducing defect density comparably to atomic layer deposition. TFTs fabricated entirely by sputtering at 200 °C demonstrate high performance: saturation mobility of 14.5 cm 2 ·V −1 ·s −1 , on/off ratio of 8.6 × 10 6 , subthreshold swing of 0.09 V/dec, and good bias stability. Resulting inverters show full‐swing operation, sensitive dynamic response, excellent frequency stability, and a voltage gain exceeding 12. This strategy provides a promising solution for low‐temperature, fully‐sputtered all‐oxide TFTs compatible with flexible displays.