Demonstration of Asymmetric Gate-Oxide Thickness Four-Terminal FinFETs Having Flexible Threshold Voltage and Good Subthreshold Slope

摘要

Flexibly controllable threshold-voltage $(V_{rm th})$ asymmetric gate-oxide thickness $(T_{rm ox})$ four-terminal (4T) FinFETs with $hbox{HfO}_{2} [hbox{equivalent oxide thickness (EOT)} = hbox{1.4} hbox{nm}]$ for the drive gate and $hbox{HfO}_{2} + hbox{thick} hbox{SiO}_{2} (hbox{EOT} = hbox{6.4}$–$hbox{9.4} hbox{nm})$ for the $V_{rm th}$-control gate have been successfully fabricated by utilizing ion-bombardment-enhanced etching process. Owing to the slightly thick $V_{rm th}$-control gate oxide, the subthreshold slope $(S)$ is significantly improved as compared to the symmetrically thin $T_{rm ox}$ 4T-FinFETs. As a result, the asymmetric $T_{rm ox}$ 4T-FinFETs gain higher $I_{rm on}$ than that for the symmetrically thin $T_{rm ox}$ 4T-FinFETs under the same $I_{rm off}$ conditions.