Design space exploration of FinFETs in sub-10nm technologies for energy-efficient near-threshold circuits

Near-threshold (near-V_TH) operation of circuits by scaling the supply voltage (V_DD) leads to maximum energy efficiency of the digital systems [1]. However, since the device characteristics are different in super-threshold (super-V_TH) and near-V_TH regions, devices optimized for standard V_DD operation may be sub-optimal for low V_DD operation [2]. Hence, there is a need to perform circuit-aware device design for near-V_TH transistors. In this paper, we explore the design space of transistors in deeply scaled technologies (nominal gate length of 5nm) for nearVTH operation. We choose FinFETs for our study due to their excellent short channel characteristics. A detailed analysis of device circuit interactions is carried out using our simulation framework based on tight-binding bandstructure calculations, quantum ballistic models for devices and circuit simulations in HSPICE. We show the dependence of energy dissipation in near-VTH circuits on different device parameters. Based on our analysis, we discuss the design methodology for near-VTH devices.