Low-Frequency Noise Characterization of Ultra-Low Equivalent-Oxide-Thickness Thulium Silicate Interfacial Layer nMOSFETs

Low-frequency noise measurements were performed on n-channel MOSFETs with a novel ultra-low 0.3-nm equivalent-oxide-thickness (EOT) interfacial layer (TmSiO) and two different bulk high-
$k$
dielectrics (Tm
₂
O
₃
and HfO
₂
). The MOSFETs were fabricated in a gate-last process and the total gate-stack EOT was 1.2 and 0.65 nm for the Tm
₂
O
₃
and HfO
₂
samples, respectively. In general, both gate-stacks resulted in 1/
$f$
type of noise spectra and noise levels comparable with the conventional SiO
₂
/HfO
₂
devices with similar EOTs. The extracted average effective oxide trap density was
$2.5\times 10^{17}$
and
$1.5\times 10^{17}$
cm
$^{\mathrm {-3}}$
eV
$^{\mathrm {-1}}$
for TmSiO/HfO
₂
and TmSiO/Tm
₂
O
₃
, respectively. Therefore, the best noise performance was observed for the gate-stack with Tm
₂
O
₃
bulk high-
$k$
layer and we suggest that the interface free single-layer atomic layer deposition (ALD) fabrication scheme could explain this.