Comparative Study on Indium Precursors for Plasma-Enhanced Atomic Layer Deposition of In₂O₃ and Application to...

Indium oxide (In₂O₃) is a transparent wide-bandgap semiconductor suitable for use in the back-end-of-line-compatible channel layers of heterogeneous monolithic three-dimensional (M3D) devices. The structural, chemical, and electrical properties of In₂O₃ films deposited by plasma-enhanced atomic layer deposition (PEALD) were examined using two different liquid-based precursors: (3-(dimethylamino)propyl)-dimethyl indium (DADI) and (N,N-dimethylbutylamine)trimethylindium (DATI). DATI-derived In₂O₃ films had higher growth per cycle (GPC), superior crystallinity, and low defect density compared with DADI-derived In₂O₃ films. Density functional theory calculations revealed that the structure of DATI can exhibit less steric hindrance compared with that of DADI, explaining the superior physical and electrical properties of the DATI-derived In₂O₃ film. DATI-derived In₂O₃ field-effect transistors (FETs) exhibited unprecedented performance, showcasing a high field-effect mobility of 115.8 cm²/(V s), a threshold voltage of -0.12 V, and a low subthreshold gate swing value of <70 mV/decade. These results were achieved by employing a 10-nm-thick HfO₂ gate dielectric layer with an effective oxide thickness of 3.9 nm. Both DADI and DATI-derived In₂O₃ FET devices exhibited remarkable stability under bias stress conditions due to a high-quality In₂O₃ channel layer, good gate dielectric/channel interface matching, and a suitable passivation layer. These findings underscore the potential of ALD In₂O₃ films as promising materials for upper-layer channels in the next generation of M3D devices.