Impact of using adaptive body bias to compensate die-to-die Vt variation on within-die Vt variation

Abstract

Scaling of supply voltage (Vdd) is essential for controlling active power dissipation in complex digital circuits. Transistor threshold voltage (Vt) variation is one of the key limiters to Vdd scaling. Several adaptive body bias in schemes have been proposed earlier to reduce the impact of die-to-die Vt variation. Unfortunately, body bias degrades the short channel effect (SCE) in the MOSFET. As technology is scaled down, this adverse effect of body biasing poses an increasingly serious challenge to controlling SCE and results in worse within-die Vt variation. The scaling trends of body bias values required to reduce die-to-die Vt variations and the resulting increase in within-die Vt variation are presented across three different technology generations.