Inhibitor-Assisted Atomic Layer Deposition for Uniformly Doped Ultrathin Films: Overcoming Compositional and Thickness Limitations

Abstract

Achieving uniform dopant distribution and fine compositional tuning in atomic layer deposition (ALD) processes remains a significant challenge, particularly for ultrathin films, due to their cyclic nature. This study systematically investigates the inherent limitations of compositional uniformity and the minimum thickness achievable in depositing doped films using ALD. Furthermore, a strategy is implemented to resolve the compositional nonuniformity in the ALD-grown doped films by employing inhibitors. Utilizing Sn-doped In₂O₃ films as the model system, this approach examines the influences of carboxylic acids, including acetic acid, isobutyric acid, and 2-ethylbutyric acid, as inhibitors, resulting in a significant reduction of the growth per cycle of a SnO_x doping layer to 1/10 to 1/20 of the levels observed without inhibitors. The degree of inhibition correlates with the size of the carboxylic acid, allowing precise control over dopant composition and enabling uniform doping in films as thin as 2 nm. Also, atomistic simulations reveal that steric hindrance plays as the major inhibition mechanism among the carboxylic acids, providing mechanistic insights into the design criteria for optimal inhibitors. The results suggest that inhibitor-assisted ALD processes offer a viable pathway to improve dopant control and alleviate thickness limitations, enhancing the performance of advanced materials.