Spin Transfer Technologies: next up in the MRAM race

by Robin Harris on Wednesday, 19 April, 2017

MRAM technology is hot. I’ve written about Everspin – they’ve been shipping for years and just IPO’d – and now I’d like to introduce Spin Transfer Technologies. They’ve kept a low profile – they AREN’T shipping, are sampling protos, and they do have some nice Powerpoints. I spoke to their CEO, Barry Hoberman, and the VP Engineering, Bob Warren, last week.

Context
STT was founded in 2012, based on IP that NYU incubated for years. Their primary funder is the IP commercialization firm Allied Minds. (IP commercialization is a newish business model too.) Here’s a word from Allied Minds:

Allied Minds is a private equity-funded innovation company that forms, funds, manages and builds startups based on early-stage technology developed at renowned U.S. universities and national labs. Allied Minds serve as a diversified holding company that supports its businesses with capital, management and shared services and is the premier firm to utilize this novel and fully-integrated approach to technology commercialization.

STT has raised $109 million and is embarked on an 8 year development plan. Their secret sauce is

. . . a proprietary OST-MRAM™ (orthogonal spin transfer MRAM) that offers a much higher speed-power-endurance operating point than other conventional perpendicular ST-MRAM technologies. The result: MRAM operating speeds matching those of SRAM cache memories — but without the endurance and data retention limitations or excessive power consumption of other MRAM implementations.

A long game
A company that started in 2012 with an 8 year development program is planning to ship in 2020. They have developed working devices that they are sampling so potential customers can get an idea of what their technology can do.

Which is? The first market for OST-MRAM is as an SRAM replacement. Their big advantage there is density: an MRAM cell is 6-10x smaller than an SRAM cell. But SRAM is also fast, so STT is working to get their parts down to a 10ns cycle time. Not easy. Current MRAM is in the ≈30ns range.

STT also believes they have other key advantages over other MRAM and ReRAM technologies as well.

One is a better write error rate. According to STT:

. . . setting a magnetic polarization vector is a probabilistic event—writing an MRAM cell one trillion times will mostly work, but very occasionally may not. One of the biggest challenges with MRAM technology is making the write error rate (WER) as low as possible, and also compensating for the few errors that will occur.

STT believes they have a solid answer to this problem, which will make them competitive.

Another issue is the tension between write speed, power consumption, and endurance. Fast writes require more power, and more power reduces cell endurance. So technology that reduces WER, also helps write speed, power, and endurance.

The StorageMojo take
One of the points STT makes is that magnetic tunnel junctions do not require atoms to move, unlike ReRAM and PCM, and that MTJ technology is already widely used in disk drive heads. So maybe the HDD folks have the inside track.

STT also thinks they have a shot at replacing DRAM. The claim is that there are just 2-3 more processing steps over CMOS to make MRAM, so the costs should be competitive, while lower power consumption will seal the deal.

But the early market will be IoT and SRAM replacement. They aren’t the only ones targeting IoT, but the concept is certainly viable.

Bottom line: the NVRAM market is heating up. And that’s a very good thing for the IT industry.

Courteous comments welcome, of course.

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