13.3 A 7Mb STT-MRAM in 22FFL FinFET Technology with 4ns Read Sensing Time at 0.9V Using Write-Verify-Write Scheme and Offset-Cancellation Sensing Technique

摘要

STT-MRAM has been emerging as a very-promising high-density embedded nonvolatile memory (eNVM) [1, 2]. Embedded Flash memory has been the leading eNVM technology, but STT-MRAM has been developed as a better solution for continuing scaling, speed and cost. This paper presents a write-verify-write (WvW) scheme and a programmable offset cancellation sensing technique that achieves a high-yield, high-performance and high-endurance 7Mb STT-MRAM arrays in a 22FFL FinFET technology [3]. The developed technology supports a wide range of operating temperatures between -40 - 105°C. Compared to priorart [4,5], the two-stage current-sensing technique with a die-by-die tuning of a thin-film precision resistor that is used as a reference can significantly improve the sensing margin during verify and read operations. Read disturb for reference cells is eliminated as there is no MTJ in the reference path.