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.
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
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".
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:
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.
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.
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’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, 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 will integrate the new technology into its Hprobe ATE systems to drastically enhance the sorting flow of STT-MRAM wafers at major 300mm foundries.
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.
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.
Phison Electronics ships over 600 million NAND flash controllers annually.
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.
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.
Everspin Technologies announced that it completed the development activity and entered the pilot production phase of its 28 nm 1-Gigabit (Gb) STT-MRAM chips. Everspin targets the enterprise infrastructure and data center markets which can utilize its MRAM technology to increase reliability and performance.
Everspin 1-Gb chip family (EMD4E001G) includes both 8-bit and 16-bit DDR4 compatible (ST-DDR4) interface versions of the device and are available in a JEDEC-compliant BGA package.
pMTJ STT-MRAM developer Avalanche Technology announced that it closed its latest funding round led by Thomvest Ventures, having raised $33 million.
Avalanche currently brands its MRAM chips as P-SRAM (persistent SRAM) devices. The new funds will enable the company to develop higher-density P-SRAM devices. In addition, Avalanche says it will develop the higher densities of "persistent DRAM" required for the next generation of machine learning architectures.
Everspin announced its financial results for Q4 2018. Revenues in the quarter grew 21% from last year to reach $12.3 million, while total year revenues in 2018 grew 38% from 2017 to reach $49.4 million. Net loss in the quarter was $3.5 million (down from $4.4 million in Q4 2017). Net loss for the whole 2018 was $17.8 million (down from $21.1 million in 2017).
Everspin says that it has increased the production volume of its 40nm 256Mb STT-MRAM in support of its lead flash array customer. Everspin ended 2018 with with cash and cash equivalents of $23.4 million.
In October 2018 Intel revealed that it is developing embedded MRAM - and that the company has successfully integrated embedded MRAM into its 22nm FinFET CMOS technology on full 300mm wafers.
Now Intel gave more details on its embedded STT-MRAM, and said that the technology is ready for high-volume manufacturing. Intel said it has used a "write-verify-write" scheme and a two-stage current sensing technique to create 7Mb perpendicular STT-MRAM arrays in its 22FFL FinFET process.