STT-MRAM

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.

Image
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".

Image
STT-MRAM chips

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

ITRI joins forces with TSMC and NYCU to develop next-gen MRAM technologies

Taiwan's Industrial Technology Research Institute (ITRI) announced two new MRAM collaborations. The first one is with Taiwan's TSMC, for the development of SOT-MRAM array chips. The second collaboration is with National Yang Ming Chiao Tung University (NYCU) to develop magnetic memory technology that can perform across a wide operating temperature range of nearly 400 degrees Celsius.

Together with TSMC, ITRI is developing low-voltage and current SOT-MRAM, that features high write efficiecny and low write voltage. ITRI says that its SOT-MRAM achieves a writing speed of 0.4 nanoseconds and a high endurance of 7 trillion reads and writes. The memory also offers a data storage lifespan of over 10 years.

Read the full story Posted: Jun 28,2022

Renesas develops 22-nm circuit technologies for embedded STT-MRAM

Renesas announced that it has developed 22-nm embedded STT-MRAM circuit technologies. Renesas developed a test 32-megabit (Mbit) chip with an embedded MRAM memory cell array that achieves 5.9-nanosecond (ns) random read access at a maximum junction temperature of 150°C, and a write throughput of 5.8-megabyte-per-second (MB/s).

Image
32Mb MRAM by Renesas, macro photo

To achieve this performance, Renesas developed two technologies. The first is a fast read technology employing high-precision sense amplifier circuit, utilizing capacitive coupling. The second is a fast write technology, with simultaneous write bit number optimization and shortened mode transition time.

Read the full story Posted: Jun 18,2022

ISI introduces a new 3-Axis magnet option for its MRAM tester systems, targeting STT-MRAM and SOT-MRAM testing

Integral Solutions International (ISI) announced a new 3-Axis Magnet Option for wafer-level testing. Combined with ISI's WLA5000 Tester, the 3D magnetic fields produced by this system can be used for characterization of MRAM devices in addition to 2D/3D Magnetic Sensors.

ISI WLA5000 MRAM tester

ISI says that for MRAM applications, the 3D Magnetic fields produced by ISI’s 3-Axis Magnet Option delivers solutions for both STT-MRAM and SOT-MRAM applications.

Read the full story Posted: Mar 04,2022

Everspin reports its Q4 2021 financial results

Everspin Technologies announced its financial results for Q4 2021. Revenues in the quarter came in at $18.2 million (up from $14.8 million in Q3 2021,and $10 million in Q4 2020). During the quarter, the company recognized $3.95 million in the IP monetization deal it signed in Q3 2021. The company reports Q4 positive net income of $3.7 million. Cash and equivalents at the end of the quarter increased to $21.4 million (up from $14.6 million in the end of 2020).

Everspin Technologies chip photo

Everspin has seen excellent Toggle MRAM shipments and revenue, but the company's STT-MRAM was flat as its largest customer was also impacted by supply constraints (not related to Everspin). The company expects STT-MRAM revenue to remain flat for the new couple of quarters. It expects Q1 2022 revenues to be in the range of $13.4 million to $14.2 million.

Read the full story Posted: Mar 03,2022

Researchers from Tohoku University developed the world's smallest STT-MRAM MTJ

Researchers from Tohoku University managed to fabricate the world's smallest STT-MRAM MTJ, at 2 nm. In addition, the researchers demonstrated fast switching (3.5 ns) in sub-five-nm STT-MRAM MTJs.

10-nm MTJ TEM photo, Tohoku University

The new MTJ were developed using a new multilayered ferromagnetic structure that can engineer characteristic relaxation time, which governs the magnetization dynamics in the ns regime.

Read the full story Posted: Dec 14,2021

Hprobe launches a next-generation MRAM wafer sort magnetic test head

Hprobe announced a new magnetic test head for MRAM Wafer Sort. The new module, the H3DM-XL, is at the heart of the latest addition to Hprobe’s IBEX line, the IBEX-WS.

Hprobe MRAM Wafer-Sort Magnetic Test Head (IBEX-WS)

The IBEX-WS test equipment integrates 3D magnetic field capabilities, while increasing field area and uniformity for wafer probing large MRAM arrays. It also features a unique patented robotized 3D Field Calibration Unit (FCU) for high-speed field mapping and monitoring.

Read the full story Posted: Dec 01,2021

Avalanche and LinearASICs to co-develop companion chiplets for Avalanche's Space Grade MRAM

pMTJ STT-MRAM developer Avalanche Technology announced that it has signed an agreement with LinearASICs Inc. to develop companion chiplets to offer a complete portfolio of Space Grade products with SPI and DDR interfaces, based on Avalanche's 1Gb Space Grade MRAM.

Avalanche pMTJ STT-MRAM P-SRAM Serial QSPI Evaluation Kit photo

Avalanche's 2nd-Gen P-SRAM evaluation kit

LinearASICs will provide standalone serial interface chiplets such as Octal SPI (OSPI), as well as standard memory interface chiplets such as DDR. These chiplets will be available as standalone devices or integrated modules through Avalanche.

Read the full story Posted: Sep 22,2021

Everspin reports its financial results for Q2 2021, its first profitable quarter

Everspin Technologies announced its financial results for Q2 2021. Revenues were $11.85 million, up 15% over Q1 2021 (and similar to Q2 2020), as STT-MRAM revenues jumped 56%. Net profit was $0.25 million, up from a loss of $0.46 million in Q1 2021 (and $1.29 million in Q2 2020).

Everspin Technologies chip photo

At the end of Q2 2021, Everspin had $14.2 million in cash and equivalents, down from $15.5 million from the end of Q1 2021. Cash flow from operations was negative at $0.56 million. Looking into the next quarter, Everspin expects revenues to be in the range of $11.7 million to $12.8 million.

Read the full story Posted: Aug 13,2021

Orthogonal Spin Transfer MRAM developer Spin Memory liquidates

Orthogonal Spin Transfer MRAM (OST-MRAM) technology developer Spin Memory is shutting down. The company's main investor and founding company, Allied Minds, said in a statement that the main reasons challenges in securing new customers and COVID-19 which "significantly delayed the required testing of its development chip with ARM".

MRAM by Spin Memory photo

This is a sad ending to Spin Memory, which began its way as Spin Transfer Technologies - a spin-off from NYU that was established together with Allied Minds.

Read the full story Posted: Jul 15,2021