Physical compact modeling and analysis of velocity overshoot in extremely scaled CMOS devices and circuits

Abstract

A compact physics-based velocity-overshoot model is developed, implemented in metal oxide semiconductor field-effect transistor (MOSFET) circuit models, verified based on measured current-voltage data and Monte Carlo-simulation results, and demonstrated in performance projections for 25 nm bulk-Si complementary metal-oxide-semiconductor (CMOS). The demonstration, involving predicted current-voltage characteristics and ring-oscillator propagation delays, reveals a significant benefit of velocity overshoot, or quasi-ballistic transport, in extremely scaled nMOS and even pMOS devices, although the on-state currents are well below the ballistic limits. Physical insight afforded by the model reveals why the ballistic limits are not being reached in scaled bulk-Si CMOS technologies.