Low-Thermal-Budget High-Mobility In2O3 Thin-Film Transistors Enabled by an In Situ Multifunctional Protection Layer

While atomic layer deposition (ALD)-grown In2O3 thin-film transistors (TFTs) hold great promise for next-generation electronics, the performance and reliability of highly desirable top-gate configurations are often limited by interfacial degradation caused by photolithography chemicals and plasma exposure during device fabrication. Here, a multifunctional protection layer (PL) strategy is demonstrated that simultaneously suppresses chemical and plasma-induced interfacial damage while enabling controlled hydrogen incorporation. The introduction of an in situ plasma-free thermal ALD Al2O3 (T-Al2O3) layer directly onto the In2O3 channel, a robust physical barrier against chemical and plasma damage is established while simultaneously serving as a hydrogen reservoir. Crucially, inserting this T-Al2O3 layer allows for the precise tailoring of hydrogen incorporation by modulating the ALD cycles. The incorporated hydrogen effectively passivates interfacial defects, such as oxygen vacancies (VO) and oxygen interstitials (Oi), while optimizing the carrier concentration. Consequently, the optimized top-gate TFTs deliver an exceptionally high field-effect mobility of 66.7 cm2/V·s, hysteresis-free operation, and outstanding operational stability, with a positive bias temperature stress (PBTS)-induced Von shift of only 0.26 V and excellent resistance to negative-bias illumination stress (NBIS). Notably, these outstanding characteristics are achieved through a completely thermal annealing-free process. These results establish a powerful platform for simultaneous chemical and plasma damage suppression and hydrogen engineering in oxide semiconductor devices, enabling substantial improvements in both electrical performance and operational reliability.