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Carbon nanotube chips ready for production

Posted: 04 Jun 2008     Print Version  Bookmark and Share

Keywords:carbon nanotube chips  foundry  CMOS 

Carbon nanotube chips appear ready for commercialisation, claims the 'first' foundry offering carbon nanotube thin films to fabless chip makers.

Nantero Inc. partnered with SVTC Technologies to offer the first eight-inch nanotube thin-film development foundry. SVTC uses Nantero's process to prototype commercial CMOS carbon nanotube designs for fabless chip houses.

"SVTC's partnership with Nantero enables us to offer a carbon nanotube process to third parties as a vehicle to their chip development efforts," said Bert Bruggeman, SVTC vice president of operations and general manager.

SVTC said its first customer is prototyping a carbon nanotube-based random-access memory (NRAM). Nantero claims NRAMs could be up to 20 times denser than current flash memories using 22-nm square bit cells compared to 100-nm cells for current 16-Gbit flash memories. That's a whopping 320-Gbit/chip densities for NRAM using current lithography.

Using next generation lithography, Nantero claims nanotube thin films could ultimately be capable of terabit-per-chip capacities by squeezing bit cells down to as small as 5-nm square.

Carbon nanotube ribbons can either deform to touch electrodes, marking a one, or remain planar by not touching an electrode, marking a zero.

"Beyond NRAM, there are also applications in displays, touch screens, solar cells, sensors and MEMS devices," said Greg Schmergel, Nantero co-founder, president and CEO. "Our process puts carbon nanotube thin films on a variety of substrates in a manner that can be mass-produced in any CMOS foundry. You can make the films thinner and thicker, change their density, even make them trasparent for displays and touch screens," he claimed.

Commercial carbon nanotubes are first purified in Nantero's process and sorted before being fabricated into a chip monolayer. Normal masking and etching steps are used to pattern carbon nanotube films on chips like other semiconductor materials—with circuitry fabricated using the nanotubes enjoying the higher electron mobility of carbon compared to silicon.

For NRAMs, carbon nanotube thin film is patterned as a strip suspended over each bit cell composed of a air cavity with a metal electrode at the bottom. The suspended carbon nanotubes are attracted to the electrode by electrostatic forces, deforming but not damaging the film, so that it shorts out against the electrode and is held there by van der Waal forces even when power is removed. The process makes NRAMs nonvolatile.

Because nanotubes are very flexible, the electrostatic force can be reversed to force the deformed nanotubes back up, making the film planar again and disconnecting it from the electrode. Nantero claims nanotubes are unique in allowing an unlimited number of such on/off deformations.

Besides NRAMs, carbon nanotube films are good candidates for applications like interconnection layers below the 45-nm process node where carbon nanotube thin films may outperform copper interconnects. The films also could be used to make cheap, durable touch screens, replacing indium tin oxide in flat panels for electron-field-emission displays. Other proposed applications include paper-thin batteries, super-efficient solar cells and for ultra-sensitive sensors.

Nantero was founded in 1999. It has raised Rs.126.07 crore ($31.5 million) in three financing rounds between 2001 and 2005. It currently employs 60 workers.

- R. Colin Johnson
EE Times

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