PGIREM: Reliability-Constrained IR Drop Minimization and Electromigration Assessment of VLSI Power Grid Networks Using Cooperative Coevolution

Abstract

Due to the resistance of metal wires in power grid network, voltage drop noise occurs in the form of IR drop which may change the output logic of underlying circuits and may affect the reliability performance of a chip. Further, it is necessary to handle different reliability constraints while designing a robust power grid network for a chip. Any violation of such constraints may increase the occurrences of IR drop. Therefore, there is a need to minimize the IR drop without violating the reliability constraints. In this paper, the IR drop minimization problem is formulated as a single objective large-scale variable minimization problem subjected to different reliability constraints, such as IR drop constraints, electromigration constraints, minimum width constraints, metal area constraints. At first, the large-scale minimization problem is divided into several subproblems using a divide and conquer based decomposition strategy, called Cooperative Coevolution. Secondly, each subproblem is solved using self-adaptive differential evolution with neighborhood search. Finally, electromigration (EM) assessment is done for the power grid networks using Black's equation to demonstrate the optimism in the predicted time-to-failure (TTF) after minimization of the IR drop.