Comparative Study on Indium Precursors for Plasma-Enhanced Atomic Layer Deposition of In₂O₃ and Application to High-Performance Field-Effect Transistors

Abstract

Indium oxide (In 2 O 3 ) 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 In 2 O 3 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 In 2 O 3 films had higher growth per cycle (GPC), superior crystallinity, and low defect density compared with DADI-derived In 2 O 3 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 In 2 O 3 film. DATI-derived In 2 O 3 field-effect transistors (FETs) exhibited unprecedented performance, showcasing a high field-effect mobility of 115.8 cm 2 /(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 2 gate dielectric layer with an effective oxide thickness of 3.9 nm. Both DADI and DATI-derived In 2 O 3 FET devices exhibited remarkable stability under bias stress conditions due to a high-quality In 2 O 3 channel layer, good gate dielectric/channel interface matching, and a suitable passivation layer. These findings underscore the potential of ALD In 2 O 3 films as promising materials for upper-layer channels in the next generation of M3D devices.