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
$>\,\,{1}\times {10} ^{{9}}$
. 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 (ID) degrades and threshold voltage (VT) shifts positively under PBS. The degradation of ID is attributed to the field-induced oxygen adsorption during PBS while VT is mainly determined by oxygen absorption and acceptor-like trap formation. The transistor reliability is significantly enhanced by a 1.5 nm Al2O3 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.