MTJ-based nonvolatile logic-in-memory circuit, future prospects and issues

Nonvolatile logic-in-memory architecture, where nonvolatile memory elements are distributed over a logic-circuit plane, is expected to realize both ultra-low-power and reduced interconnection delay. This paper presents novel nonvolatile logic circuits based on logic-in-memory architecture using magnetic tunnel junctions (MTJs) in combination with MOS transistors. Since the MTJ with a spin-injection write capability is only one device that has all the following superior features as large resistance ratio, virtually unlimited endurance, fast read/write accessibility, scalability, complementary MOS (CMOS)-process compatibility, and nonvolatility, it is very suited to implement the MOS/MTJ-hybrid logic circuit with logic-in-memory architecture. A concrete nonvolatile logic-in-memory circuit is designed and fabricated using a 0.18 mum CMOS/MTJ process, and its future prospects and issues are discussed.