Move over, NAND flash memory. Santa Clara-based startup Crossbar, Inc. has developed a non-volatile memory technology based on resistive random-access memory. Dubbed Crossbar RRAM, the tech promises 20X the write performance of NAND flash memory with 10X the endurance. RRAM isn't just a distant speck on the horizon, either. According to the Crossbar press release, a working test chip has already been produced. Company CEO George Minassian says Crossbar RRAM is "easy to manufacture and ready for commercialization," as well.
The Crossbar tech is based on RRAM patents licensed exclusively from the University of Michigan. Each cell sandwiches an insulating switching medium between electrode layers. Applying a voltage to those electrodes causes nanoparticles in the switching medium to form a conductive filament between them. The simple cell structure is amenable to stacking, according to Crossbar, and it can be scaled down to fabrication nodes smaller than five nanometers.
NAND endurance tends to diminish at smaller cell geometries, but longevity shouldn't be a problem for Crossbar RRAM. There's no need to erase the contents of cells before reprogramming them, which should cut down on write/erase cycles. The cells themselves are quite robust, too. Crossbar claims they can withstand one million write cycles. That figure likely refers to single-bit applications, but RRAM also supports MLC configurations with multiple bits per cell. The memory type's claimed 20-year data retention looks pretty solid, too.
Crossbar touts RRAM's easy integration with SoC circuitry, and the firm seems intent on providing on-chip storage for smartphone and tablet processors. Its first product will be an embedded SoC. SSDs—and particularly enterprise-oriented drives—are also mentioned as potential applications.
RRAM's prodigious storage potential makes it particularly appealing for PC applications. Crossbar says the technology can squeeze up to a terabyte onto a single, 200-mm² chip, though it doesn't detail the number of layers or the fabrication process required to achieve that feat. For the 25-nm chip pictured above, which is presumably a single-layer implementation, Crossbar RRAM more than doubles the storage density of NAND flash.
Flash memory is big business these days, but its limited write endurance presents a very real challenge to scaling down to smaller process geometry. RRAM looks like an attractive alternative, especially if SoC integration is as easy as advertised. We'll have to see how long it takes Crossbar to get RRAM products on the market—and how much they cost per gigabyte, of course. If you're curious about Crossbar RRAM, you can read more about it in this whitepaper (PDF).
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