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Nanotube fab looks forward to multiple chip apps

Posted: 04 Jun 2008 ?? ?Print Version ?Bookmark and Share

Keywords:nanotube? chipmakers? foundry? applications?

Carbon nanotube chips appear ready for commercialization, claiming the first foundry offering carbon nanotube thin films to fabless chipmakers.

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, VP operations and general manager, SVTC.

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

Using next-generation lithography, Nantero noted that nanotube thin films could ultimately be capable of terabit-per-chip capacities by squeezing bit cells down to as small as 5nm 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, touchscreens, solar cells, sensors and MEMS devices," said Greg Schmergel, co-founder, president and CEO, Nantero. "Our process puts carbon nanotube thin films on a variety of substrates where they can be mass produced in any CMOS foundry. You can make the films thinner and thicker, change their density, even make them transparent for displays and touchscreens," he stressed.

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 materialswith 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 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 claimed nanotubes are unique by allowing an unlimited number of such on/off deformations.

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

Nantero was founded in 1999. It has raised $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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