STT-MRAM (also called STT-RAM or sometimes ST-MRAM and ST-RAM) is an advanced type of MRAM devices. STT-MRAM enables higher densities, low power consumption and reduced cost compared to regular (so-called Toggle MRAM) devices. The main advantage of STT-MRAM over Toggle MRAM is the ability to scale the STT-MRAM chips to achieve higher densities at a lower cost.

STT-MRAM has the potential to become a leading storage technology as it is a high-performance memory (can challenge DRAM and SRAM) that can scale well below 10nm and challenge the low cost of flash memory.



What is STT-MRAM?

STT stands for Spin-Transfer Torque. In an STT-MRAM device, the spin of the electrons is flipped using a spin-polarized current. This effect is achieved in a magnetic tunnel junction (MTJ) or a spin-valve, and STT-MRAM devices use STT tunnel junctions (STT-MTJ). A spin-polarized current is created by passing a current though a thin magnetic layer. This current is then directed into a thinner magnetic layer which transfers the angular momentum to the thin layer which changes its spin.

STT-MRAM structure diagram

What is perpendicular STT-MRAM?

A "regular" STT-MRAM structure (similar to the one you see above) uses an in-plane MTJ (iMTJ). Some STT-MRAM devices use a more optimized structure called perpendicular MTJ (pMTJ) in which the magnetic moments are perpendicular to the silicon substrate surface.

Perpendicular STT-MRAM is more scalable compared to iMTJ STT-MRAM and is also more cost competitive. Perpendicular STT-MRAM is thus a more promising technology to replace DRAM and other memory technologies

STT-MRAM chips

Several companies, including IBM and Samsung, Everspin, Avalanche Technologies, Spin Transfer Technologies and Crocus are developing STT-MRAM chips. In April 2016 Everspin announced that it started shipping 256Mb ST-MRAM samples to customers. The new chips demonstrate interface speeds comparable to DRAM, with DDR3 and DDR4 interfaces. Volume production is expected "soon".

Everspin EMD3D256 256Mb ST-MRAM photo

In August 2016 Everspin started sampling pMTJ-based ST-MRAM chips. The first chips are also 256Mb in size, but the pMTJ versions offer improved performance, higher endurance, lower power, and better scalability compared to previous iMTJ ST-MRAM products. Everspin is now ramping out 256Mb pMTJ ST-MRAM production and is developing a scaled-down 1Gb version.

Latest STT-MRAM news

Everspin reports its financial results for Q3 2017, focuses on 256Mb STT-MRAM

Nov 14, 2017

Everspin reports its financial results for Q3 2017. Revenues reached a record $9 million (up from $7.2 million in Q3 2016 and up only slightly from last quarter), while the net loss grew to $5.4 million (up from $1.4 million in Q3 2016).

Everspin  Q3 2017 earnings slide

At the end of the quarter, Everspin had $17.8 million in cash and equivalents (down from $21.2 million at the end of Q2 2017). Everspin expects revenue in Q4 2017 to be in the range of $9.9 million to $10.3 million.

Spin Transfer Technologies and Tokyo Electron to co-develop next-gen STT-MRAM devices

Oct 16, 2017

Spin Transfer Technologies (STT) announced that it has signed an agreement with Tokyo Electron (TEL) to collaborate on the development of next-generation SRAM and DRAM-class STT-MRAM devices.

Spin Transfer Technologies says that the combination of its STT-MRAM technology with TEL’s advanced PVD MRAM deposition tool will allow the companies to quickly develop processes for the highest density and endurance devices.

A new European project aims to develop a system-level STT-MRAM exploration flow

Oct 12, 2017

The EU launched a new project called GREAT H2020 moderated by the CEA-Spintec laboratory that plans to co-integrate multiple functions like sensors, RF receivers and logic/memory together within CMOS thanks to a single baseline technology in the same System on Chip.

MAGPIE process image

One of the project’s final objectives is to develop a system-level simulation and design of a representative IoT platform, integrating this technology. To achieve it, a unique exploration flow is proposed: MAGPIE. MAGPIE stands for Manycore Architecture enerGy and Performance evaluation Environment and has been jointly developed and funded through GREAT and the CONTINUUM ANR French project.

Spin Transfer Technologies raised $22.8 million via a convertible bridge facility

Oct 06, 2017

Spin Transfer Technologies announced that it has raised $22.8 million via a convertible bridge facility. STT says that this will help the company get ready to complete its Series B funding round, targeting strategic investors and planned to conclude by end of Q1 2018.

In January 2017 STT announced that it has started to deliver fully functional ST-MRAM samples to customers in North America and Asia. The sample devices are based on the company's Orthogonal Spin Transfer Magneto-Resistive Random Access Memory technology (OST-MRAM), and use 80nm perpendicular magnetic tunnel junctions (MTJs)., the latest generation of MRAM technology.

Seagate demonstrate an MRAM-powered high performance SSD boot drive

Aug 15, 2017

Seagate demonstrate several new prototypes and technologies at Flash Memory Summit last week, and one of these is the new Nytron 5000B SSD drive that is a high-performance boot drive. The new device has 256GB of 3D MLC NAND and makes use of 1258MB of Everspin's STT-MRAM in addition to a "normal" DRAM cache.

Seagate SSD with MRAM cache prototype (August-2017)

Seagate says that the MRAM can be used as either a write cache for user data or it can be exposed directly as a separate storage namespace for explicit tiered storage. Seagate said that this is currently just a test-platform prototype - and not a preview of an upcoming product.

Everspin starts to sample 1Gb pMTJ STT-MRAM chips

Aug 10, 2017

Everspin announced that it started sampling 1Gb STT-MRAM chips. Everspin's new chips provide a high-endurance, persistant memory with a DDR4-compatible interface. Everspin sees these chips being used in storage devices to provide protection against power loss without the use of supercapacitors or batteries.

Everspin 128Kb automotive MRAM photo

Everspin's new pMTJ 1Gb chips provide 4 times the capacity of the company's current 256Mb DDR3 chips. The 1 Gb MRAM is produced in 28nm CMOS on 300mm wafers in partnership with GlobalFoundries.

GlobalFoundries and Everspin say that the pMTJ STT-eMRAM features high reliability at high temperatures

Jun 30, 2017

GlobalFoundries has plans to deploy Everspin's perpendicular (pMTJ) STT-MRAM as an embedded 22nm memory - as part of GF's 22FDX platform. GlobalFoundries has released a technical paper that details the eMRAM ability to retain data at high temperatures.

Global Foundries 22nm eMRAM slide

The eMRAM can retain data through solder reflow at 260 degrees Celsius, and for more than 10 years at 125 degrees Celsius, plus read/write with outstanding endurance at 125 degrees Celsius. GlobalFoundries says that this will enable eMRAM to be used for general purpose MCUs and automotive SOCs.

Samsung reaffirms 2018 target for STT-MRAM mass production

May 26, 2017

During Samsung Electronic's Foundry Forum, the Korean chip maker reaffirmed its goal to start producing STT-MRAM chips in 2018. In fact Samsung now says that it will mass produce these chips next year, while last year it said that 2018 will only see limited production while real mass production will only begin in 2019.

Samsung announced it will produce the 2018 MRAM chips will be produced using 8-nano low power plus (8LMPP) semiconductor foundry process. Samsung sees MRAM produced by 4LPP by 2020.