First Demonstration of Multi-VT Stacked Ge0.87Sn0.13 Nanosheets by Dipole-Controlled ALD WNxCy Work Function Metal with Low Resistivity and Thermal Budget ≤ 400 °C

Dipole-controlled WN
x
C
y
work function metal (WFM) by plasma-enhanced atomic layer deposition (PEALD) is integrated with stacked GeSn nanosheet transistors to enable multi-V
T
with a wide tunability of 510 mV at the low process temperature ≤ 400 °C. The effective work function (EWF) of WN
x
C
y
is modulated by the relative thicknesses of pWFM and nWFM while maintaining the constant total thickness. EWF tuning of 500 meV around Si midgap is obtained, and the best achievable resistivity of ALD WN
x
C
y
is 990 μΩ-cm, much lower than industrial ALD TiAl value (2000 μΩ-cm [1]). Multi-V
T
stacked Ge
0.87
Sn
0.13
nanosheets are demonstrated by controlling the different group electronegativity and dipole strength at nWFM/WN
x
C
y
:O interface.