Spin-transfer torque magnetic random access memory (STT-MRAM)

TLDR

STT‑MRAM is a scalable, nonvolatile memory that builds on the existing MRAM platform, offering fast read/write, sub‑6F cell sizes, and compatibility with DRAM and SRAM architectures while adding minimal cost. This review surveys current STT‑MRAM technologies worldwide and demonstrates that the in‑plane DMTJ design is mature enough to meet conventional nonvolatile memory requirements. The authors examine existing STT‑MRAM developments, including results from Grandis and foundry partners, and show that the in‑plane DMTJ design satisfies all conventional performance criteria. Recent advances in perpendicular STT‑MRAM suggest it could mature faster than anticipated, enabling even smaller cell sizes and earlier product introduction at advanced nodes.

Abstract

Spin-transfer torque magnetic random access memory (STT-MRAM) is a novel, magnetic memory technology that leverages the base platform established by an existing 100+nm node memory product called MRAM to enable a scalable nonvolatile memory solution for advanced process nodes. STT-MRAM features fast read and write times, small cell sizes of 6F 2 and potentially even smaller, and compatibility with existing DRAM and SRAM architecture with relatively small associated cost added. STT-MRAM is essentially a magnetic multilayer resistive element cell that is fabricated as an additional metal layer on top of conventional CMOS access transistors. In this review we give an overview of the existing STT-MRAM technologies currently in research and development across the world, as well as some specific discussion of results obtained at Grandis and with our foundry partners. We will show that in-plane STT-MRAM technology, particularly the DMTJ design, is a mature technology that meets all conventional requirements for an STT-MRAM cell to be a nonvolatile solution matching DRAM and/or SRAM drive circuitry. Exciting recent developments in perpendicular STT-MRAM also indicate that this type of STT-MRAM technology may reach maturity faster than expected, allowing even smaller cell size and product introduction at smaller nodes.