P‐229: Late‐News Poster: Improved PBTS Reliability of Dual‐Gate a‐IGZO TFT by Bottom Interface Optimization

Amorphous transparent oxide TFT based on a‐IGZO has been widely used in OLED display fields. In practical applications, we find that compared with the single top gate structure, the dual‐gate a‐IGZO TFT has higher current to meet strict display requirements, but the reliability will deteriorate to limit its further development. Firstly, we confirm that under PBTS test, the bottom channel interface of dual‐gate IGZO TFT exhibits significantly larger Vth shifts than the top channel interface (top and bottom channel contributions are 0.11V and 0.63V, respectively). The worse reliability is mainly due to the damage to the interface caused by ion bombardment during a‐IGZO deposition, which inevitably generates a large amount of unbonded or free oxygen at the interface. These defects trap carriers accumulating negative charges at the interface, thereby shielding part of the gate electric field and causing Vth shift. Therefore, we propose that by increasing the hydrogen content in the bottom gate insulation layer, more hydrogen diffused to the interface can passivate the excess oxygen defect. The significant improvement results show that the Vth shift of dual‐gate IGZO TFT under PBTS decreases from 0.81V to 0.41V.