Power Supply Voltage Dependence of Within-Die Delay Variation of Regular Manual Layout and Irregular Place-and-Route Layout

Dependence of within-die delay variations on power supply voltage (VDD) is measured down to 0.4V. The VDD dependence of the within-die delay variation of manual layout and irregular auto place and route (P&R) layout are compared for the first time. The measured relative delay (=sigma/average) variation difference between the manual layout and the P&R layout decreases from 1.56% to 0.07% with reducing VDD from 1.2V to 0.4V, because the random delay variations due to the random transistor variations dominate total delay variations instead of the delay variations due to interconnect length variations at low VDD.