Nantero’s Carbon-Nanotube-Based Chips Could Outdo Other Types of Computer Memory
Instant-on computers. Laptops that eat up less battery power. Cell phones that store a selection of movies. Those are the benefits Nantero hopes to bring to consumers by creating a new type of computer memory that combines the speed and density of SRAM and DRAM chips with the permanent storage capacity of flash memory. The Woburn, MA-based company is building computer memory with carbon nanotubes, which it says will provide advantages that other memory technologies can’t.
“There’s a growing need for more and more memory in portable devices,” says Greg Schmergel, CEO of Nantero. “In a few years, it’ll be common to talk about how many terabytes you have.”
That’s the vision that Schmergel has been pursuing since founding Nantero in 2001 along with a pair of chemistry Ph.D.s from Harvard, Thomas Rueckes and Brent Segal. Since then, the company has amassed 60 employees, 50 patents (and another 100 pending), and $31.5 million in funding from investors including Charles River Ventures, Globespan Capital Partners, Draper Fisher Jurvetson, and Stata Venture Partners. The company also has growing revenues from licensing its technology (more on that in a moment) and from a partnership with Brewer Science of Rollo, MO, which manufacturers carbon nanotubes for electronics manufacturers to use in designing and building their own products.
Nantero is working on what it calls NRAM, or nonvolatile random access memory; the technology was invented by Rueckes, who’s now the company’s CTO. Like flash memory, which is common in digital cameras, NRAM will hold data indefinitely without drawing any power, but can easily be rewritten when the power’s turned on. But it will have far more storage capacity and will work much faster.
NRAM makes bits out of pairs of carbon nanotubes. One nanotube is fixed to the surface of the chip, another stands up perpendicular to the first. Give one nanotube a negative charge and the other a positive charge, and the upright nanotube bends down and touches the other. Because of physical forces at this tiny scale, measured in billionths of a meter, the two nanotubes stick together and stay that way, unless a new pulse of electricity gives them the same charge and they repel one another. The closed and open pairs represent the ones and zeros of digital data.
“You’re moving a few hundred carbon atoms over distances measured in billionths of a meter,” Schmergel says. It takes only a little power and a short time to do that, making the data-writing process fast and easy. The speed and power advantages alone make NRAM superior to today’s flash memory, he says.
But more important is the fact that NRAM will be able to go to even smaller sizes, packing more memory into the same space. “Flash is hitting the scaling wall,” says Schmergel. “It’s becoming ever more difficult to scale it and make it smaller. By contrast, scaling NRAM is quite simple.”
Packing in more memory is a matter of inscribing smaller features in the layer of carbon nanotubes deposited on the silicon chip. Schmergel says the technology should work with features down to about 5 nanometers in size. Most flash memory is working with features measuring 65 nanometers, though the industry is trying to move to 45 nanometers.
The NRAM technology is designed to be compatible with the current computer chip manufacturing process. Manufacturers would lay down a thin layer of nanotubes on top of a silicon substrate, then use standard photolithography and chemical etching to inscribe the lines that make up various circuits on the chip. “There’s nothing that the semiconductor fabs haven’t seen before other than the carbon nanotube material,” Schmergel says. The technology has to be compatible with current processes if Nantero wants to gain a foothold in the well-established chipmaking industry, which he admits is an enormous challenge. “That’s why we’ve made all of the effort to make sure our memory could be made in today’s fabs, using only the existing equipment and the existing people.”
Indeed, Nantero doesn’t build any memory itself. It’s licensing its technology to a number of partners, including Hewlett-Packard; ASML, the Netherlands-based maker of chip-making equipment; and BAE, a major international manufacturer of electronic systems for consumers and military customers. The partners are developing the processes for making NRAM chips, and have already produced some test chips. Schmergel says he’ll leave it up to the partners to announce when they’ll have products ready for the market, but that the first should show up within a couple of years. “It’s in the near future,” he says, “unlike most nanotech, which is many years away.”
One possible near-term product might be an NRAM-based solid-state drive for a computer laptop. Solid-state drives are available today, based on flash technology, but they cost more and hold much less data than a standard hard drive.
“Most observers of the laptop industry believe that solid-state drives are going to eventually be a huge segment of the market,” Schmergel says. “Hopefully, we’ll be the ones who will convince you to replace your hard drive with a solid-state drive.”
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