Higher-Capacity Memory

A new type of memory could soon be available to device makers.

Sharp memory: Ultrasharp silicon tips like this one, which is just 10 nanometers wide, are the core of a new memory technology that could soon provide an alternative to flash. Credit: Nanochip

An alternative to the flash memory that stores and retrieves data with arrays of microscopic probes could soon be on the market. Nanochip, a company based in Fremont, CA, has recently raised $14 million to complete work on prototypes that it hopes to ship to electronics device makers for evaluation next year.

Nanochip's technology offers advantages to flash memory, both in terms of the amount of data that can be stored and the cost per memory chip, says Gordon Knight, the company's CEO. The first prototypes will store about 100 gigabytes, he says--more than the tens of gigabytes stored on flash memory cards today. Eventually, the devices could store terabytes' worth of data, he says. That's likely out of the reach of flash-type memory, says Stefan Lai, formerly the director of flash memory technology at Intel and now a scientific advisor to Nanochip.

In flash memory, information is stored using specialized transistors, each of which is addressed by a grid of conducting wires. The Nanochip technology, in contrast, stores information by writing data to a thin-film material using an array of microscopic cantilevers, each with an extremely sharp tip. The size of each bit will be 15 nanometers in the first devices, but it could theoretically be as small as just a couple of nanometers.

Nanochip's array-based memory provides an alternative to both flash memory and hard drives. In addition to storing more data than flash, it will be cheaper and can be about as fast, Knight says. What's more, it could last longer than flash. Compared with hard drives, the manufacturing processes used will make Nanochip's devices more economical for small portable electronics, Lai says. The company's memory devices would also be more rugged than hard drives and run virtually silently.

The idea of using microscopically sharp tips to store data is not new. In the late 1990s, IBM demonstrated its Millipede technology, which used arrays of a thousand such tips to write and read bits. (See "Bugged about the Future of Magnetic Storage?") The Millipede program is still active at IBM but so far hasn't produced a commercial memory chip. Nanochip uses a similar approach.

However, while IBM's Millipede uses a polymer material, with data stored by heating and indenting the material with the ultrasharp tip, Nanochip uses a material that can be written electronically: applying a voltage through the tip changes the electronic state of the material at the point of contact. That state can later be read using a weaker voltage. Knight says that the electronic process is faster than a thermal process.

A remaining challenge is engineering a complete chip with thousands of cantilevers. The arrays will need to be mounted on a stage that can be moved, using electrostatic forces, over the storage material and combined with electronics that make it possible to control each tip separately. Part of the challenge will be writing the algorithms for controlling the device to optimize how to store data using the moving stage, says William King, professor of mechanical science and engineering at the University of Illinois at Urbana-Champagne. (King was part of the Millipede team at IBM and is a scientific advisor to Nanochip.) In both hard drives and flash memory, he says, bits can be accessed sequentially. But in this system, to take advantage of the parallel arrays of tips, methods of storing and retrieving thousands of bits at once will need to be developed.

"It's a big challenge, but it's something I believe can be done," Lai says. "And if you solve the problems, then you have a whole new memory technology that's available."

http://www.technologyreview.com/Nanotech/20192/