Cold temperature power on reset use case

Abstract

This work describes a use case study of a failing mixed-signal product that showed instability in the power-on-reset signal at cold temperatures. It is a marginal fail whose root-cause turned out to be larger than expected random variations in threshold voltage, that cause a mismatch between matched transistors in a comparator in a band-gap circuit. The fail was localized with OBIRCh in an SDL-like setup. Understanding the origin of the fail required transistor characterization, and device simulation. Further, FIB circuit-edit was used to prove that the fail could be resolved with a metal fix. This use case is representative of the multi-faceted aspects of failure analysis of mixed-signal devices. It highlights the cross-disciplinary team-effort required for the successful identification of the root-cause of a fail. Further, it is also a testament of the wide range of tools and techniques needed for the resolution of a failing product.