Are on-chip power-ground planes really needed? A signal integrity perspective

We use the on-chip bus characterization methodology of to study the impact of the on-chip power distribution system on the signal integrity of a 12-line bus. We compare two power supply systems implemented in the same Cu BEOL stack: an entirely grid-based system and a system similar to in that it contains one metal layer dedicated to V_dd and one metal layer dedicated to V_ss. We show that while the dedicated power/ground layers do contribute to the mitigation of the inductive and return-path impedance effects, the ultimate signal integrity of the on-chip bus depends on the interplay between resistive losses, electromagnetic couplings (capacitive and inductive), and the driving and receiving circuitry.