Monitoring of aging in integrated circuits by identifying possible critical paths

Abstract

Aging of integrated circuits can no longer be neglected in advanced process technologies. Especially the strong dependence of the delay degradation of digital circuits on the workload is still an unsolved problem. If the workload is not known exactly, only a worst-case design can guarantee that the circuit works correctly during the entire specified lifetime. We propose a method that enables a better-than-worst-case design. To assure that this design still works correctly during the specified lifetime, the circuit is monitored periodically and countermeasures are taken if the circuit degrades too much. Our main contribution is an algorithm to identify all paths that might become critical during the specified lifetime. These are called possible critical paths (PCPs). This is the first approach that also considers local process variations for finding the PCPs. Without considering process variations, it is not guaranteed that all possible critical paths are found. In addition, we could reduce the number of paths that have to be monitored by 2.7× compared to a state-of-the-art approach.