Improving the Thermal\nStability of Indium Oxide n‑Type\nField-Effect Transistors by Enhancing Crystallinity through Ultrahigh-Temperature\nRapid Thermal Annealing

Ultrathin indium oxide films show great potential as\nchannel materials\nof complementary metal oxide semiconductor back-end-of-line transistors\ndue to their high carrier mobility, smooth surface, and low leakage\ncurrent. However, it has severe thermal stability problems (unstable\nand negative threshold voltage shifts at high temperatures). In this\npaper, we clarified how the improved crystallinity of indium oxide\nby using ultrahigh-temperature rapid thermal O<sub>2</sub> annealing\ncould reduce donor-like defects and suppress thermal-induced defects,\ndrastically enhancing thermal stability. Not only does more crystalline\nindium oxide depict the high stability of threshold voltage in stringent\nhigh-temperature test environments and under positive bias, but it\nalso shows much less degradation under forming gas annealing than\nas-deposited transistors. Furthermore, we also successfully solved\nthe channel length-dependent threshold voltage problem, which is often\nobserved in oxide transistors, by suppressing defects induced by the\nmetal deposition process and metal doping.