Everspin Technologies Inc. (Chandler, Arizona) has said it will be in volume production of the industry's first spin-transfer torque magnetoresistive RAM, a 64-Mbit memory in a DDR3 format, in the second half of 2014.
The company, a 2008 spin-off from Freescale Semiconductor Inc. (Austin, Texas), has also revealed that sales of embedded MRAM – where Everspin adds MRAM to CMOS logic wafers processed at other foundries – is exceeding sales of stand-alone MRAM.
Everspin started to sample STT-MRAM back in November 2012 but all of its volume shipments of MRAM are still of its earlier, "toggle" MRAM devices.
MRAM, a non-volatile memory that stores data after power is removed, is attracting the interest of both startups and major memory vendors. Because data is stored as a magnetic state rather than electronic charge, the memory cells do not suffer the wear-out or data retention issues associated with flash technology. The memory chip market leaders including Micron, Samsung, SK Hynix and Toshiba seem to be pitching STT-MRAM as a DRAM replacement at large capacities and aggressive geometries. However, none has yet brought the technology to market. STT-MRAM is considered superior to conventional MRAM by way of lower power consumption and better scalability. Samsung acquired STT-MRAM pioneer Grandis Inc. in August 2011 but has still not brought its technology to market.
This together with the slowness of Everspin's transition to volume have given rise to suggestions that STT-MRAM, with its magnetic materials, may be hard to get to high yield in wafer fabs.
Speaking at Embedded World exhibition in Nuremberg, Germany, Scott Sewell, vice president of worldwide sales at Everspin, said: "It is taking longer than we anticipated but we are also dependent on customers' development of applications. We will see spin-torque in volume in the second half of 2014."
In November 2013 Everspin announced that its 64-Mbit STT-MRAM had been designed into solid-state drive (SSD) from Buffalo Technology (USA) Inc. (Austin, Texas) as cache memory. Sewell added that the ability to embedded STT-MRAM in 90nm CMOS would follow within a year of the stand-alone parts hitting volume.
The 64-Mbit STT-MRAM, part numbered EMD3D064M, is manufactured by Everspin in a 90nm process. Everspin uses foundry vendors for front-end production and does magnetic layer and back-end processing of the STT-MRAM on its 200-mm production line. It can be seen that stand-alone production is similar to the production of embedded MRAM in SoCs.
The EMD3D064M is functionally compatible with the industry standard JEDEC specification for the DDR3 interface, which delivers a memory bandwidth of up to 3.2Gbytes/second. It is the first product on a roadmap that is intended to scale to gigabit capacities. The company is jumping to 40nm process for a 256-Mbit and Sewell said Everspin is working with a number of customers on bring up MRAM on a 28nm process.
Since its spin off from Freescale Everspin has raised about $45 million in venture capital but the company is also making revenue from sales of toggle MRAM and embedded toggle MRAM. Sewell said he expected Everspin to reach breakeven in 2014 but declined to comment on whether or how quickly an initial public offering of Everspin stock might follow.
However, Sewell indicated that sales are on an upward ramp that will be boosted when STT-MRAM hits volume.
He said that Everspin has shipped more than 12 million stand-alone MRAMs. This compares with about 7 million that had shipped by November 2012. And SoCs with Everspin's MRAM embedded have totalled more than 19 million units, Sewell said. "Mainly we are replacing battery-backed SRAM in an SoC. By switching to MRAM the user gets the same functionality and can throw out the coin cell in the equipment," he said. This reduces the PCB footprint and can make equipment simpler to qualify because it no longer contains at least one hazardous component, Sewell said.