Electromigration simulation and design considerations for integrated circuit power grids

Due to continued technology scaling, electromigration has become a serious reliability concern in modern integrated circuits. This is further aggravated by the pervasive use of inaccurate models for electromigration based on traditional empirical black-box models. We will review the modern approach to electromigration verification, with emphasis on recent physical models, then summarize our work on a finite-difference based approach for power grid electromigration checking using these models. The method simulates the electromigration damage across the power grid, much like simulating for voltage or current. The lifetimes found using this physics-based approach are on average about twice or more than those based on the traditional empirical approaches. Because this approach is computationally efficient, one is able to handle large grids with millions of branches. We then present detailed analysis of the steady-state stress and its relation to voltages and currents in the grid, along with a number of design considerations that follow from this analysis.