The Hump Phenomenon and Instability of Oxide TFT Were Eliminated by Interfacial Passivation and UV + Thermal Annealing Treatment

Abstract

In this work, we propose a simple and efficient interfacial modification method for thin-film transistor (TFT)-1 with poor stability under bias stress. For conventional top-contact TFT-2, the sputtering passivation layer will cause the device to be in a short-circuit condition. We used inverted coplanar-structured TFT-3 to separate the high conductivity layer from the S/D electrodes to avoid the short-circuit failure of the device, but this will cause a hump effect. Ultraviolet treatment and air annealing were performed on TFT-3 simultaneously to obtain TFT-4 with high mobility (μsat = 45.5 cm2 V–1 s–1), steep subthreshold swing (SS = 86 mV/dec), and good bias stability (±20 V, 3600 s, NBS: −0.1 V, PBS: +0.9 V, PGDBS: +0.5 V). The forward and reverse tests of TFT-1 and TFT-4 after the PGDBS test show that TFT-4 has a good stability of the asymmetric electrical bias. Finally, XRR, XPS, AFM, and contact angle were tested to further investigate the material mechanisms. In this paper, we show that the interfacial passivation of TFT can effectively isolate the invasion of external water/oxygen and compensate for interfacial defects and dangling bonds. The decomposition and rearrangement of the oxide are induced by UV + thermal annealing, which optimizes the stacking pattern of the cells, effectively reducing the defect states and eliminating parasitic channels and the hump phenomenon. Finally, an amorphous oxide semiconductor (AOS)-TFT instrument with high mobility and good stability is prepared. The method in this paper addresses the problem that the passivation layer cannot be prepared by sputtering, which is a cost-effective process.