Vertically Stacked Gate-All-Around Structured Tunneling-Based Ternary-CMOS

Abstract

This article proposes a novel structure for tunneling-based ternary-complementary metal-oxide-semi conductor (T-CMOS) to break through the power scaling constraints of conventional binary-CMOS. The previous T-CMOS uses off-leakage band-to-band tunneling (BTBT) currents generated at the deep drain-to-substrate junction for the third voltage state, which allows ternary inverter configuration with only two single transistors. However, the high-dose ion implantation for the BTBT layer must affect the channel doping concentration, leading to the threshold voltage fluctuation. To avoid the interference of the BTBT layer dopants to the channel as well as to maximize the electrostatic gate controllability, vertically stacked gate-all-around (GAA) field-effect transistor (GAAFET)-type T-CMOS device is proposed. By simply changing the ground plane (GP) doping concentration in existing GAAFET fabrication, the BTBT layer can be formed completely apart from the suspended channel layers. The changes of the transfer characteristics and the transient output voltage characteristics depending on the key parameters such as the GP doping concentration and the gate work function are thoroughly analyzed for the proposed GAA T-CMOS through mixed-mode TCAD device and circuit simulations. It is concluded that the two key parameters should be optimized, otherwise the margin for the third voltage state and the switching speed is seriously degraded.