Reversible Thickness Engineering in Amorphous In₂O₃ Transistors

Amorphous oxide semiconductors offer a unique platform for versatile device processing, as their noncrystalline nature eliminates the requirement for lattice matching at the interface and enables low-temperature regrowth and isotropic processing. Leveraging chemical continuity of amorphous surface, this study demonstrates atomic-scale, reversible thickness control of amorphous In₂O₃ by integrating bottom-up atomic layer deposition with top-down hydroxide-assisted wet-etching processes. The processes achieve bidirectional modulation of the film thickness from 1 to 4 nm under back-end-of-line compatible conditions while maintaining smooth surfaces (R_a = ∼0.5 nm) and stable chemical composition. This thinning-regrowth process enables precise, thickness-dependent control over the In₂O₃ transistor performance, facilitating doping-free modulation of the threshold voltage and reversible switching between depletion- and enhancement-mode operation within a single device. Successful demonstration of inverters and ring oscillators confirms the robustness of this technique, establishing film thickness as a core design parameter for oxide semiconductors and paving the way for reconfigurable electronics.