Plasma-enhanced atomic layer deposition of indium-free ZnSnOx thin films for thin-film transistors

• We studied atomic layer deposition for multi-component ZTO thin film transistors. • The number of reaction sites affects the mass gained in each ALD cycle. • High electron mobility was achieved even in the enhancement-mode operation. • CMOS inverter demonstrated using atomic layer deposited channel layers. An appropriate synthesis technique for growing high-quality indium-free ZnSnO x (ZTO) films should be developed to achieve high-performance thin-film transistors (TFTs) utilizing ZTO films. This study investigated the growth characteristics and electrical properties of ZTO thin films grown via plasma-enhanced atomic layer deposition (PEALD) using bis(1-dimethylamino-2-methyl-2-propoxide)Sn, diethylzinc, and O 2 plasma to optimize the composition and enhance the device performance. Deviations were observed in the growth per cycle when using PEALD for ZTO, compared with binary oxides. In the PEALD of the ZTO films, the introduction of the SnO 2 sub-cycle enhanced the mass gain in the ZnO sub-cycle, whereas the mass gain in the SnO 2 sub-cycle decreased with the addition of the ZnO sub-cycle. This was attributed to changes in the density of the functional groups on the reaction surface. Precise control over the composition was achieved, enabling the identification of the optimal Zn 58 Sn 42 O x composition. Post-deposition annealing significantly improved the TFT performance, with devices showing enhanced mobility, positive shifts in the threshold voltage, and reduced subthreshold swing values. These improvements stemmed from reductions in oxygen vacancies and sub-gap defect states. These findings highlight the potential of PEALD-grown ZTO films for use in high-performance, cost-effective TFTs, facilitating their integration into modern semiconductor electronics.