【Device Papers】Passivation-Dependent Device-Level Thermal Robustness of Indium Gallium Oxide Thin-Film Transistors under Dynamic Random-Access Memory Relevant 600 °C Nitrogen Annealing

      Researchers from Hanyang University have published a dissertation titled " Passivation-Dependent Device-Level Thermal Robustness of Indium Gallium Oxide Thin-Film Transistors under Dynamic Random-Access Memory Relevant 600 °C Nitrogen Annealing " in ACS Applied Materials & Interfaces.

Abstract

      As conventional silicon-based dynamic random-access memory (DRAM) approaches its physical and electrical scaling limits, oxide semiconductors have emerged as promising channel materials for next-generation memory devices because of their low off-state current and process compatibility. Among them, indium gallium oxide (IGO) thin-film transistors (TFTs) have attracted considerable attention for DRAM-related applications; however, their implementation remains challenging because the device stack must withstand high-thermal-budget back-end-of-line processing, including annealing at 600 °C in a N₂ ambient which can promote oxygen-deficient conditions in oxide layers. Here, we systematically investigate the effects of passivation-layer selection on the electrical performance and thermal reliability of IGO TFTs by comparing Al₂O₃-, HfO₂-, and SiO₂-passivated devices before and after 600 °C N₂ annealing. Among the passivation layers examined, Al₂O₃ uniquely preserved stable transistor operation after the high-temperature process, whereas the HfO₂- and SiO₂-passivated devices exhibited severe degradation of switching behavior and became electrically unextractable after 10 min annealing. In contrast, the Al₂O₃-passivated TFTs retained excellent electrical characteristics, including a field-effect mobility of 94.08 cm²V^–1s^–1 and a subthreshold swing of 84 mVdec^–1 after 10 min annealing. Moreover, the positive-bias temperature stress stability was markedly improved, with the threshold-voltage shift at 100 °C decreasing from 63 to 20 mV after extended annealing. The superior reliability of Al₂O₃ layer may be attributed to its strong Al–O bonding and high film density, which provide enhanced chemical and structural stability during high-temperature N₂ annealing. These findings suggest that Al₂O₃ passivation is an effective strategy for enabling thermally robust and electrically reliable IGO TFTs for advanced DRAM applications.

DOI：

https://doi.org/10.1021/acsami.6c10253