BEOL Compatible Ultra-Thin ITO Transistor with Performance Recoverable Capability by in situ Electrothermal Annealing

Gate bias instability, a well-known issue in oxide semiconductors, is linked to their inherent sensitivity to oxygen species. In this work, we systematically investigated the reliability of back-end-of-line (BEOL) compatible ultra-thin ITO transistor, showing near-ideal minimum subthreshold swing (SS) of 63 mV/dec and high on/off ratio > 1×10 ⁹ . The degraded transistor performance after 1000 s positive gate bias (PBS) is fully recovered utilizing an in situ electrothermal annealing (ETA) method, which can also enhance ITO transistor performance. The transistor drain current (I _D ) degrades and threshold voltage (V _T ) shifts positively under PBS. The degradation of I _D is attributed to the field-induced oxygen adsorption during PBS while V _T is mainly determined by oxygen absorption and acceptor-like trap formation. The transistor reliability is significantly enhanced by a 1.5 nm Al ₂ O ₃ passivation coating as oxygen barrier. Our results elucidate the degradation mechanism of ultra-thin ITO transistor and offer an applicable solution, paving the way for ITO in BEOL monolithic 3D integration for next generation ICs.