Scaling characteristics of fnqs and ft in NMOSFETs with and without supply voltage scaling

Abstract

Extensive process and device simulations are performed to investigate the nonquasi-static transition frequency (fNQS) behaviour of the NMOSFETs at different technology nodes, 0.5 mm to 90 nm, having same off-state leakage current (IOFF). These studies are done with and without supply voltage scaling. fNQS exhibits a turnaround in the 100 nm regime when we do the supply voltage scaling along with the transistor scaling. We attribute this effect to the reduced gate overdrive (VGS-Vt) and thereby to the degraded transconductance (gm). The unity gain frequency (ft) also shows a similar trend. The turnaround effect of fNQS and ft disappears when IOFF is allowed to go up or the gate overdrive is increased or both.