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

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

Avalanche announces space-grade Gigabit-density STT-MRAM

pMTJ STT-MRAM developer Avalanche Technology announced its third-generation 1Gb space-grade parallel asynchronous x32-interface high-reliability P-SRAM (Persistent SRAM) memory devices. The company says that these new devices enable customers to design unified memory architecture systems for high reliability aerospace applications, in extremely small form factors.

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

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

The new Parallel x32 Space Grade series is offered in 512Mb, 1Gb, 2Gb and 4Gb density options and has asynchronous SRAM compatible 45ns/45ns read/write timings. Data is always non-volatile with >10^14 write cycles endurance and 10-year retention at 125°C. All four density options are available in a small footprint 142-Ball FBGA (17mm x 11mm) package.

Read the full story Posted: Jun 16,2021

Avalanche has been awarded four key "milestone" STT-MRAM patents

Avalanche Technology has been awarded four key "milestone" patents for its STT-MRAM technology and solid-state storage array system design. Avalanche has over 200 filed patents that covers the full spectrum from memory cell/circuit design and manufacturing to solid-state storage system development and deployment.

Avalanche (founded in 2006 and based in California, US) developed patented Spin Programmable STT-MRAM (SPMEM) memory that uses a revolutionary proprietary spin current and voltage switching technology. The company wants to license their technology for embedded applications and also build discrete standalone memory devices. In July 2012 the company raised $30 million.

Read the full story Posted: Mar 26,2014

Avalanche has been awarded four more key STT-MRAM patents

Last month we reported that Avalanche Technology has been awarded four key "milestone" patents for its STT-MRAM technology and solid-state storage array system design. Today the company announced that it has been awarded four new STT-MRAM patents in areas of Perpendicular STT-MRAM and MRAM Integration and Manufacturing. Avalanche has over 200 filed patents that covers the full spectrum from memory cell/circuit design and manufacturing to solid-state storage system development and deployment.

The company has been awarded three key patents in the area of Perpendicular STT-MRAM:

Read the full story Posted: Apr 22,2014

Avalanche raises $30 million to bring their STT-MRAM products to market

Avalanche Technology announced that it has raised $30 million from existing investors (Vulcan Capital, Sequoia Capital, Bessemer Venture Partners, Thomvest Ventures and Qualcomm Ventures) and also from a new investor, VTB capital. Avalanche hopes that this investment will enable them to bring the first products into the market.

Avalanche will produce STT-MRAM chips based on their proprietary SPMEM (Spin Programmable Memory) technology. SPMEM uses a revolutionary spin current and voltage switching technology that enables "lower write current, smaller cell size and excellent scalability". The first products will use a 65 nm process, but the company says that their technology is scalable to 10 nm or even less.

 
Read the full story Posted: Aug 01,2012

Avalanche starts production of space-grade 16-64Mb STT-MRAM devices

pMTJ STT-MRAM developer Avalanche Technology announced that it is now shipping new space-grade parallel asynchronous x16-interface high-reliability P-SRAM (Persistent SRAM) memory devices, based on its latest STT-MRAM technology.

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

Avalanche says that its STT-MRAM devices are smaller and more efficienct compared to Toggle MRAM based products, currently adopted in aerospace applications. The Parallel x16 Space Grade series is offered in 16Mb, 32Mb and 64Mb density options and has asynchronous SRAM compatible 45ns/45ns read/write timings. All three density options currently in production and available within industry standard lead times.

Read the full story Posted: May 05,2021

Avalanche Technology announces its 2nd-generation pMTJ STT-MRAM chips at 1-32 Mb densities

pMTJ STT-MRAM developer Avalanche Technology announced its 2nd-generation serial non-volatile discrete MRAM memory family. The SPnvSRAM family offers 1 Mb to 32 Mb densities at extended-temperature industrial-grade specifications. Avalanche says that these devices, available in low pin count, small package options, are ideal for a broad range of industrial, automotive and consumer applications.

Avalanche Technology SPnvSRAM G2 MRAM evaluation board photo

Avalanche's 2-Gen SPnvSRAM is offered in 108-MHz Quad Serial Peripheral Interface (QSPI) performance as a byte addressable memory thus eliminating the need for software device drivers.

Read the full story Posted: Nov 18,2018

Avalanche Technology raises $33 million in a new funding round

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.

Read the full story Posted: Jun 03,2019

Avalanche Technology starts to sample 32/64 Mbit STT-MRAM chips

STT-MRAM developer Avalanche Technology announced that it began to sample STT-MRAM chips. Avalanche's proprietary perpendicular magnetic tunnel junction (pMTJ) cells are manufactured in a high volume, low cost, standard CMOS 300mm process.

Those first sample chips are 32Mbit and 64Mbit in size, and offer an industry-standard SPI interface built on a 55nm-node foundry process. Avalanche is also offering its STT-MRAM technology (which they brand as AvRAM) under license as embedded memory for integrated SOC designs.

Read the full story Posted: Jul 03,2015