Crossbar Inc. (Santa Clara, Calif.) was formed in 2010 to commercialize research led by Professor Wei Lu at the University of Michigan. Professor Lu cofounded the company and serves as its chief scientific officer. Semiconductor Manufacturing International Corp. (Shanghai, China) is described as “one of Crossbar’s first foundry partners,” although it is the first to be publicly acknowledged.
The companies will now partner on integrating non-volatile Crossbar ReRAM within MCUs and SoCs within the Internet of Things, wearable and tablet computers and other consumer, industrial and automotive markets. ReRAM is expected to exhibit lower power consumption and superior performance to flash memory and also the ability to scale far below 40nm, something flash memory is not expected to do.
However, ReRAMs can be based on many different material systems and have proved difficult to bring to market. The technology has been pursued as a follow-on to flash and has been under research at large companies and at many startups for many years. When Crossbar first went public about its technology in 2013 CEO and co-founder George Minassian predicted embedded Crossbar memory in the market in 2015 and stand-alone multilayer versions of the technology about a year after that (see ReRAM Startup Bets on Silver).
Crossbar’s memory is based on silver top electrode over amorphous silicon over a polysilicon bottom electrode. The principle of operation is that a writing voltage causes silver ions to migrate through the silicon to form a filament connects the top and bottom electrodes. A reverse voltage causes the ions to move and break the connection. Lower voltages can be used to “read” the connection as a 1 or 0.
Crossbar has already demonstrated the ability to integrate a memory array above the access control circuitry and has plans to go to multilayer memory for high capacity 3D standalone memories.
“Crossbar is ready for engagement now with the RRAM PDK and in-house design services to support customized embedded memories. Crossbar is licensing memory macros to be embedded in customers’ MCU and SoCs. We expect samples this year and production ramp-up in 2017,” the company said in an email response to questions from eeNews Europe. Crossbar added that its technology does not impose capacity restrictions but that it foresees embedded memories of 256 kilobytes to 16 megabytes.
In response to a question about why Crossbar had not introduced its technology at 28nm, which does not have the commercial embedded option of flash or any other non-volatile memory, the company said: “The IoT market is one of the first segments we’re addressing and our customers foresee that the 40nm process node is going to be the sweet spot of the IoT space for at least 5 years. We also have plans to port our technology to smaller process nodes for other applications and are in discussions now to begin that process.”ulul
It has previously been reported that Crossbar would license its technology for embedded applications and come to market as a fabless vendor of stand-alone ReRAM. That may still be possible but the company is not ruling out the possibility of fabless licensees bringing stand-alone memories to market. “Our current business model with SMIC is to make our technology available to SMIC and its customers in a licensing model. While we expect customers to embed Crossbar RRAM blocks into SOC’s and MCU’s, they are not limited to using our technology in that way and certainly have the option to produce standalone devices with the license,” the company said and added “We are also in discussions now to port our technology to smaller process geometries for standalone high capacity devices and expect to announce more specific timelines for that port in the near future.”
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