In-place Repair for Resistive Memories Utilizing Complementary Resistive Switches

Recent advances in resistive memory technologies have demonstrated their potential to serve as next generation random access memories (RAM) which are fast, low-power, ultra-dense, and nonvolatile. However, owing to their stochastic filamentary nature, several sources of hard errors exist that could affect the lifetime of a resistive RAM (ReRAM). In this paper, we propose a novel mechanism to protect resistive memories against hard errors through the exploitation of a unique feature of bipolar resistive memory elements. Our solution proposes an unorthodox use of complementary resistive switches (a particular implementation of resistive memory elements) to provide an "in-place spare" for each memory cell at negligible extra cost. The in-place spares are then utilized by our repair scheme to extend the lifetime of a resistive memory. Our repair scheme detects data errors during regular memory accesses and triggers repair using the in-place spares at a page-level granularity. We show that in-place spares can be used along with other memory reliability and yield enhancement solutions, such as error correction codes (ECC) and spare rows. We develop a statistical model to evaluate our method's effectiveness on extending ReRAM's lifetime. Our analysis shows that the in-place spare scheme can roughly double the lifetime of a ReRAM system. Alternatively, our method can yield the same lifetime as a baseline ReRAM, with either significantly fewer spare rows or a lighter-weight ECC, both of which can save on energy consumption and area.