posted on 2021-08-25, 07:36authored bySeunghee Lee, Miso Kim, Geumbi Mun, Jongbeom Ko, Hye-In Yeom, Gwang-Heum Lee, Bonggeun Shong, Sang-Hee Ko Park
Atomic
layer deposition (ALD) has attracted much attention, particularly
for applications in nanoelectronics because of its atomic-level controllability
and high-quality products. In this study, we developed a plasma-enhanced
atomic layer deposition (PEALD) process to fabricate a homogeneous
indium aluminum oxide (IAO) semiconductor film. Trimethylaluminum
(TMA) and dimethylaluminum isopropoxide (DMAI) were used as Al precursors,
which yielded different compositions. Density functional theory (DFT)
calculations on the surface reactions between indium and aluminum
precursors showed that while highly reactive TMA would etch In, DMAI
with lower reactivity would allow indium to persist in the films,
resulting in a more controlled doping of Al. The In/Al composition
ratio could be further precisely controlled by adjusting the indium
precursor dose time to sub-saturation. IAO based on DMAI was applied
to fabricate thin-film transistors (TFTs), showing that Al can be
a carrier suppressor of indium oxide. TFTs with PEALD IAO containing
3.8 atomic % Al showed a turn-on voltage of −0.4 ± 0.3
V, a subthreshold slope of 0.09 V/decade, and a field effect mobility
of 18.9 cm2/(V s).