Article last updated on: Feb 19, 2019

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.

The latest STT-MRAM news:

New super-lattice SL-STT-MRAM enable faster and more efficient memory architecture

Researchers from the National Taiwan University developed a new ultra low power STT-MRAM architecture, called Super Lattice STT-MRAM, or SL-STT-MRAM. The researchers say that SL-STT-MARM simultaneously achieves ultra-high MR ratio, high-speed switching, and low RA.

SL STT MRAM structure

An SL-STT-MRAM is based on an SL-STT-MTJ, which uses a superlattice barrier to replace the single crystalline (MgO) barrier in traditional STT-MTJ. The superlattice barrier is made of alternating metal and insulator layers, in which only amorphous rather than single crystalline is used in the insulator. The SL-STT-MRAM features higher reliability for repeated writing than compared to traditional MgO based STT-MRAM.

Intel researchers demonstrate 2MB STT-MRAM arrays suitable for on-chip L4 cache applications

Intel researchers have demonstrated 2MB STT-MRAM devices that are suitable for on-chip L4 cache applications. Intel says these devices feature data retention, endurance and bit error rates good enough for L4 cache.

Intel slide - STT MRAM L4 Cache

Intel's new STT-MRAM features 20 nm write times, 4 ns read times, an endurance of 1012 cycles and memory retention of one second at 110 degrees. The bit rates are good enough to be handled with error-correcting code (ECC) techniques. To achieve these features, Intel reduced the magnetic junction size to 55 nm (from 70-80 nm it had achieved before).

Everspin announces its Q3 2019 financial results

Everspin Technologies announced its financial results for Q3 2019 - with revenues of $9.2 million (down from $11.5 million in Q3 2018) and a net loss of $3.7 million (down from $5.6 million in Q3 2018). Everspin says that it achieved record STT-MRAM revenues.

Everspin Technologies chip photo

At the end of the quarter, Everspin had $14.8 million in cash and equivalents. For the next quarter, it expects revenues to be between $9.3 million and $9.7 million.

IBM to use Everspin's 1Gb STT-MRAM in its next-gen FlashCore modules

In August 2018 IBM announced that it adopted Everspin's 256Mb STT-MRAM chips in its enterprise SSD FlashSystem. Now IBM announced that it's latest FlashCore modules will use Everspins 1Gb STT-MRAM chips.

Everspin 1Gb STT-MRAM chip photo
Using MRAM instead of DRAM memory enabled IBM to remove the relatively large supercapacitors (used to make the DRAM non-volatile) and so the company was able to reduced the size of its drives and switch to a standard 2.5-inch U.2 drive form factor.

Cadence to offer design and verification support for Everspin's 1Gb STT-MRAM

Everspin Technologies announced that Cadence Design is now providing DDR4 Design IP (DIP) and Verification IP (VIP) support for Everspin’s 1 Gb STT-MRAM memory. Cadence has supported Everspin's STT-MRAM products since 2012. Everspin customers will now be able to request 1Gb MRAM-enabled IP and VIP for their Custom ASIC solutions.

Everspin Technologies chip photo

Everspin’s 1 Gb STT-MRAM product family includes both 8bit and 16-bit DDR4 compatible (ST-DDR4) interface versions of the device and are available in a JEDEC-compliant BGA package.

Hprobe developed an ultra-fast technology for STT-MRAM device testing

Hprobe, a developer of testing equipment for magnetic devices, announced that it developed a new technology for ultra-fast (<1 second) testing of STT magnetic tunnel junctions under perpendicular magnetic field at above 2 Tesla.

Hprobe wafer prober system photo

Hprobe will integrate the new technology into its Hprobe ATE systems to drastically enhance the sorting flow of STT-MRAM wafers at major 300mm foundries.

Sage Microelectronics to add native support for Everspin's 1Gb STT-MRAM

Everspin Technologies announced a partnership with Sage Microelectronics Corporation under-which Sage will provide native support for Everspin's 1Gb STT-MRAM memory in its Enterprise Grade Flash memory controller.

Everspin 1Gb STT-MRAM chip photo

Sage provides cutting-edge, enterprise-class controllers for industries including, aerospace, automotive, industrial and data center storage solutions, offering SSD storage solutions and also delivering high-performance RAID/Port-Multiplier controllers.

Phison Electronics to add native support for Everspin's 1-Gb STT-MRAM in its next-gen SSD controller lineup

Everspin Technologies announced that Phison Electronics Corp. will provide native support for Everpsin's 1 Gb STT-MRAM memory in its next generation enterprise SSD controller lineup. Everspin says that its MRAM technology, added to Phison's controllers, will enable storage system designers to increase the reliability and performance of systems where high-performance data persistence is critical. MRAM will enable protection against power loss without the use of batteries or supercapacitors.

Everspin 1Gb STT-MRAM chip photo

Phison Electronics ships over 600 million NAND flash controllers annually.

The 2019 MRAM Developer Day will feature 1Gb MRAM parts and AI Applications

The 2019 MRAM Developer Day will be held on August 5th at the Santa Clara Convention Center (co-located
with Flash Memory Summit), and will center around Everspin's 1Gb MRAM part now in production.

Everspin 1Gb STT-MRAM chip photo

Keynotes from Everspin, Tokyo Electron, and Applied Materials will focus on MRAM as a disruptive technology and on new manufacturing tools and processes for STT-MRAM. Plenary sessions will cover the current state of MRAM technology and MRAM markets and future trends through 2025, while breakout sessions will cover applications briefs, embedded MRAM, development, and AI applications.