Comparative Study on Indium Precursors for Plasma-Enhanced Atomic Layer Deposition of InO and Application to High-Performance Field-Effect Transistors.

Indium oxide (InO) 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 InO films deposited by plasma-enhanced atomic layer deposition (PEALD) were examined using two different liquid-based precursors: (3-(dimethylamino)propyl)-dimethyl indium (DADI) and (,-dimethylbutylamine)trimethylindium (DATI). DATI-derived InO films had higher growth per cycle (GPC), superior crystallinity, and low defect density compared with DADI-derived InO 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 InO film. DATI-derived InO field-effect transistors (FETs) exhibited unprecedented performance, showcasing a high field-effect mobility of 115.8 cm/(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 HfO gate dielectric layer with an effective oxide thickness of 3.9 nm. Both DADI and DATI-derived InO FET devices exhibited remarkable stability under bias stress conditions due to a high-quality InO channel layer, good gate dielectric/channel interface matching, and a suitable passivation layer. These findings underscore the potential of ALD InO films as promising materials for upper-layer channels in the next generation of M3D devices.