Variability Analysis of Scaled Crystal Channel and Poly-Si Channel FinFETs

The threshold voltage
Vt
variability in the scaled crystal channel and poly-Si channel double-gate fin-type metal-oxide-semiconductor field-effect transistors (FinFETs) with different gate oxide thicknesses
T
_ox
has been systematically analyzed. By investigating the
T
_ox
dependence of
Vt
variations in crystal channel FinFETs, the gate-stack origin sources, i.e., work function (φ
m
) variation and gate oxide charge (
Q
_ox
) variation sources, were successfully separated. It was found that the atomically flat Si-fin sidewall channels fabricated by the orientation-dependent wet etching contribute to the reduction of gate-stack origin
Vt
variations. Moreover, it was experimentally found that the standard
Vt
deviation (σ
Vt
) of poly-Si channel FinFETs is three times higher than that of crystal channel ones, and a good subthreshold slope in the poly-Si channel FinFETs was obtained with gate length
Lg
down to poly-Si grain size.