Multi-VT of Stacked GeSn Nanosheets by ALD WNxCy Work Function Metal

The effective work function (EWF) of WN
_x
C
_y
on SiO
₂
/Si stacks can be modulated from 4.3 to 4.8 eV by plasma-enhanced atomic layer deposition. At higher annealing temperature, more oxidation of WN
_x
C
_y
near SiO
₂
can yield larger dipole with the direction from thin interfacial WN
_x
C
_y
:O to bulk WN
_x
C
_y
, and thus EWF increases. WN
_0.12
C
_0.23
with lower nitrogen content captures more oxygen atoms in the interfacial WN
_x
C
_y
from SiO
₂
than WN
_0.39
C
_0.1
and yields larger work function. Using different thicknesses of top WN
_0.12
C
_0.23
and bottom WN
_0.39
C
_0.1
with constant total thickness, the EWF can be tuned by dipole strength at WN
_0.39
C
_0.1
/WN
_x
C
_y
:O interface. The dipole-controlled WN
_x
C
_y
work function metal is integrated on the stacked GeSn nanosheets (NSs) to achieve multi-
${V}_{T}$
modulation.
${V}_{T}$
for stacked Ge
_0.87
Sn
_0.13
NSs is increasingly negative with increasing WN
_0.39
C
_0.1
thickness with a wide
${V}_{T}$
tunability of 510 mV.