Impact of cell failure on reliable cross-point resistive memory design

Resistive random access memory (ReRAM) technology is an emerging candidate for next-generation nonvolatile memory (NVM) architecture due to its simple structure, low programming voltage, fast switching speed, high on/off ratio, excellent scalability, good endurance, and great compatibility with silicon CMOS technology. The most attractive of the characteristics of ReRAM is its cross-point structure, which features a 4F² cell size. In a cross-point structure, the existence of sneak current and resulting voltage loss due to the wire's resistance might cause read and write failures if not designed properly. In addition, a robust ReRAM design needs to deal with both soft and hard errors. In this article, we summarize mechanisms of both soft and hard errors of ReRAM cells and propose a unified model to characterize different failure behaviors. We quantitatively analyze the impact of cell failure types on the reliability of the cross-point array. We also propose an error-resilient architecture, which avoids unnecessary writes in the hard error detection unit. Assuming constant soft error rate, our approach can extend the lifetime of ReRAM up to 75% over a design without hard error detection and up to 12% over the design with a "write-verify" detection mechanism. Our approach yields greater significant lifetime improvement when considering postcycling retention degradation.