RRAM Uncloaked As Super-Efficient Flash Killer

Tom Brewster is TechWeek Europe's Security Correspondent. He has also been named BT Information Security Journalist of the Year in 2012 and 2013.

Flash could soon be unseated from its throne by RRAM from start-up Crossbar

A start-up from the US has promised its memory chip technology is going to blow NAND-based Flash out of the water.

Crossbar came out of stealth mode yesterday, declaring its resistive RAM technology could squeeze 1TB of RAM on a single 200 square millimeter chip, whilst having 20 times the write speed of NAND, which still dominates the non-volatile storage space for devices like SSDs, USB drives and smartphones. The technology uses 20 times less energy than NAND too, the start-up said.

RRAM to end NAND domination?

The RRAM chips can be stacked on top of one another t0o for so-called “3D stacking” arrangements. The use of a low temperature cell allows multiple memory array layers to be integrated on top of the controller CMOS as well, Crossbar said. The very fact it uses CMOS compatible materials means it should be available, perhaps in common usage, in the next three years or so.

Actual production of the chips shouldn’t be far away, according to Crossbar, which said it had produced a Crossbar memory array at a commercial fab.

The RRAM technology differs from NAND largely in its architectural simplicity. There are no transistors as there are in NAND memory cells. Instead a cell consists of three layers: a metallic top electrode, a switching medium and a bottom non-metallic electrode.

Crossbar 2

The top electrode passes metal ions into the switching medium, creating a filament that connects the top and bottom electrodes. If that filament connection is broken with a negative charge, there is no resistance meaning the status of the cell is changed to store either a 1 or a 0.

Crossbar 1

RRAM also differs from the memristor style technology that has caused a stir in recent times. Instead of a filament between electrodes, memristor cells consist of two electrodes on either side of a chalcogenide, which can switch from amorphous to crystalline states very easily to record data.

“Non-volatile memory is ubiquitous today, as the storage technology at the heart of the over a trillion dollar electronics market – from tablets and USB sticks to enterprise storage systems,” said George Minassian, chief executive officer at Crossbar.

“And yet today’s non-volatile memory technologies are running out of steam, hitting significant barriers as they scale to smaller manufacturing processes. With our working Crossbar array, we have achieved all the major technical milestones that prove our RRAM technology is easy to manufacture and ready for commercialisation. It’s a watershed moment for the non-volatile memory industry.”

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