Logic Fault Diagnosis of Hidden Delay Defects

Hidden delay defects (HDDs) are small delay defects that pass all at-speed tests at nominal capture time. They are an important indicator of latent defects that lead to early-life failures and aging problems that are serious especially in autonomous and medical applications. An effective way to screen out HDDs is to use Faster-than-At-Speed Testing (FAST) to observe outputs of sensitized non-critical paths which are expected to be stable earlier than nominal capture time. To improve the reliability of current and future designs, it is important to learn about the population of HDDs using logic diagnosis. We present the very first logic fault diagnosis technique that is able to identify HDDs by analyzing fail logs produced by FAST. Even with aggressive FAST testing, HDDs generate only very few failing test response bits. To overcome this severe challenge, we propose new backtracing and response matching methods that yield high diagnostic success rates even with very limited amount of failure data. The performance and scalability of our HDD diagnosis method is validated using fault injection campaigns with large benchmark circuits.