The operation of an integrated circuit relies on the supply of power to the on-chip circuitry. Power distribution systems serve the purpose of supplying an integrated circuit with current while maintaining specific voltage levels. The power current is distributed across an integrated circuit through an on-chip power distribution network, an integral part of the overall power distribution system. The on-chip power distribution network delivers current to hundreds of millions of high speed transistors comprising a high complexity integrated circuit. Tens of amperes must be efficiently distributed to supply power to the on-chip circuits. Due to the high currents and high frequencies, the impedance of a power distribution system should be maintained sufficiently low over a wide range of frequencies in order to limit the voltage variations at the power load the millions of on-chip transistors.

Maintaining a low impedance over a wide range of frequencies is a complex task. Decoupling capacitors effectively reduce the impedance of a power distribution system near the capacitor resonant frequency by allowing high frequency currents to bypass high inductance interconnect structures. The decoupling capacitance and interconnect inductance, however, create tank resonant modes within a power distribution system, increasing the impedance near the tank resonant frequency. The magnitude of the tank resonance is controlled by maintaining appropriate damping characteristics within the system. The design of a low impedance power distribution system therefore requires a careful balance among the resistive, inductive, and capacitive impedances of the comprising elements.

This balance should be maintained throughout the hierarchical...