Nanotube-infused NRAM promises DRAM speeds with unlimited endurance

Since 2001, a company called Nantero has been working on making non-volatile storage with carbon nanotubes. The technology is called NRAM, and it's designed to deliver DRAM-like speeds with unlimited endurance and low power consumption.

That combination sounds too good to be true, but it's not just a pipe dream. Nantero CEO Greg Schmergel told us the firm has been working with two of the top five semiconductor foundries. Its nanotube tech is already deployed in seven production-grade fabs, he said, and multiple implementations are in different stages of qualification.

Instead of building its own products, Nantero licenses its intellectual property to others. That IP includes the "world's only method for purifying carbon nanotubes" to the standards required by CMOS fabs. This patented approach is compatible with existing fabrication tools and apparently requires no additional equipment investment.

NRAM is created by laying carbon nanotubes on top of a silicon wafer. That layer is then patterned with standard lithography and etching. On a 2x-nm node, each NRAM cell contains hundreds of nanotubes. The tiny strands can be scattered randomly with that geometry, but alignment is required to ensure adequate coverage when the feature size shrinks down to 10-nm territory.

Source: Nantero

Each cell effectively has its own nanotube fabric. The resistance is low when the nanotubes are touching and high when they're not. Applying voltage causes the cell to switch between those states in just picoseconds, according to Schmergel, and writes require a fraction of the power required by flash-based storage.

Unlike NAND, NRAM has "theoretically unlimited" endurance. Chips have already survived 1012 write cycles and 1015 reads, which might as well be infinity. They can purportedly survive just about anything, including extreme heat, cold, magnets, and radiation. A test chip has even been to outer space courtesy of an "open bay" in the Atlantis shuttle. That's some serious geek cred right there.

Although it sounds like the initial implementations will have one bit per cell, NRAM supports MLC configurations via nanotube sub-groups. Test chips have also been created with multiple layers. Interestingly, Schmergel told us that vertical stacking is a higher priority than squeezing extra bits into a single layer. Building up will apparently be required for NRAM to challenge flash memory on cost. It's supposed to be cheaper than DRAM already, though.

Some of the first NRAM products will use DDR4 interfaces. That's mostly for convenience; Schmergel said DDR4 isn't actually fast enough to fully exploit NRAM's potential. Nantero is exploring custom solutions that will.

We won't have the skinny on the first NRAM products until Nantero's partners are ready to reveal them. Schmergel told us to expect the first to be built on 2x-nm tech, so it probably won't be long before we hear something. If everything goes according to plan, the technology could be used in everything from servers to smartphones to embedded applications.

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