Design for reliability: Tradeoffs between lifetime and performance due to electromigration

Semiconductor aging and its causes have been well understood, however until recently, aging has not been a design concern. The expected lifetime of integrated circuit (IC) components has been far longer than their intended applications. As device geometries are reduced, consideration early in the design process to aging and product lifetimes become more significant for successful IC design and development, especially at 7 nm technologies. Lifetime was typically pushed at the end of the design process as signoff. Lifetime was deemed acceptable, if the electromigration rules weren't violated. This viewpoint is shifting, from what is allowed, to what the IC mission profile needs. A designer needs to know how much, more or less, lifetime tradeoff with performance, power and cost can be achieved within the mission profile constraints. This paper describes a design space exploration methodology using mission profiles that moves electromigration lifetime tradeoffs early into the design cycle, without the need to re-characterize the process, while working within the existing technology library. The main goal of these tradeoffs is to improve the IC lifetime at the expense of performance for critical applications, and increase the performance at the expense of lifetime for commercial applications.