Multi-Layer Interdigitated Power Distribution Networks

Higher operating frequencies and greater power demands have increased the requirements on the power and ground network. Simultaneously, due to the larger current loads, current densities are increasing, making electromigration an important design issue. In this paper, methods for optimizing a multi-layer interdigitated power and ground network are presented. Based on the resistive and inductive (both self- and mutual) impedance, a closed-form solution for determining the optimal power and ground wire width is described, producing the minimum impedance for a single metal layer. Electromigration is considered, permitting the appropriate number of metal layers to be determined. The tradeoff between the network impedance and current density is investigated. Based on 65-, 45-, and 32-nm CMOS technologies, the optimal width as a function of metal layer is determined for different frequencies, suggesting important trends for interdigitated power and ground networks.