Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Stanford engineers show nanotube circuits can be made en masse

Abstract:
Most innovations don't go far unless there is a way to turn them into products that are manufacturable on a mass scale. That's why new research on carbon nanotubes, presented June 19 by a group of Stanford electrical engineers, is likely to draw industry attention.

The engineers unveiled a method for making integrated circuit chips with complex nanotube components on the scale and with the parallelism that the semiconductor industry must employ to make chips that are economical.

Stanford engineers show nanotube circuits can be made en masse

PALO ALTO, CA | Posted on July 10th, 2008

"We have shown here processes that are scalable, that are akin to conventional semiconductor manufacturing on the wafer scale," said electrical engineering Professor H.-S. Philip Wong, one of the authors of a paper presented at the Symposia on VLSI Technology and Circuits in Honolulu. Wafers are the large discs of silicon on which semiconductor manufacturers pattern several hundred computer chips that are then cut out and packaged as products. "The lithography is on a wafer scale, the nanotube growth is on the wafer scale and all the processes that we use here are very similar to conventional semiconductor manufacturing," Wong said.

Because of their potential to act as high-performance transistors at higher speeds and lower power than conventional silicon technology, nanotubes are the subject of intensive research worldwide. So far, however, researchers have only been able to make nanotube circuits one at a time, rather than on the scale known as VLSI, for Very Large Scale Integration.

Moreover, the information processing components of the circuits, known as logic gates, have typically been simple inverters, rather than the whole variety of more complex gates that are needed in useful logic circuits. This new ability to make chips on a large scale with the needed variety of logic gates therefore represents an important advance toward making commercially viable nanotube integrated circuits, said Subhasish Mitra, an assistant professor of electrical engineering and of computer science.

The paper also represents the first real demonstration of a design technique that makes complex logic functional even when the nanotubes turn out to have goofy kinks and bends (rather than lying straight) or are in the wrong place. Wong and Mitra unveiled the technique last year in simulations but have now shown that it works in an actual fabrication process.

In addition to Wong and Mitra, the paper's other authors are Nishant Patil and Albert Lin, both electrical engineering graduate students, and Edward Myers, a staff member of the Stanford Nanofabrication Facility, a research fabrication facility on campus that is part of the National Nanotechnology Infrastructure Network.
Handling the heat

The Stanford-devised process involves growing nanotubes on a quartz wafer—a 4-inch diameter platter—and then transferring them like a kid's temporary tattoo onto a silicon wafer patterned with metal electrodes. The nanotubes could then connect the electrodes to make transistors and logic gates. The quartz-to-silicon transfer technology had already been established for small pieces of substrates, but what has often stymied researchers has been finding a way to grow nanotubes on such a large slab of quartz. Quartz helps facilitate nanotube growth but is sensitive to the heat required in the process.

The Stanford engineers overcame that problem by realizing that the quartz wafer would shatter like glass if it were heated too quickly as the temperature approached a certain critical point (roughly 1,100 degrees Fahrenheit). By slowing down the heating process, the researchers kept the wafers intact.

The nanotubes were then transferred to the silicon wafer to be overlaid on the electrodes. The electrodes were patterned according to special algorithms designed to ensure that however the individual nanotubes were laid out, the logic gates that were created would still work.

In all, the group created about 197 dies, or chips, on the 4-inch diameter wafer. Each chip had about 1,000 transistors, meaning that the wafer had more than 100,000 transistors. Random testing of 18 transistors per chip revealed that 99 percent of the transistors were functional. Full-scale commercial chips, of course, would require millions of transistors per chip and sophisticated interconnections among them.

Even before a full-fledged commercial nanotube chip could be designed, more research is needed to resolve some fundamental problems. Among them is a need to increase the density of nanotubes on the wafer, a goal that could be accomplished by repeated transfers from different quartz wafers to the same silicon wafer and further optimizing the nanotube growth conditions. In addition, researchers must find a way to thoroughly weed from their logic gates pesky "metallic" nanotubes, which can short-circuit transistors.

Still, the researchers are optimistic about the progress so far.

"The fundamental problem in this domain which we were able to overcome is that in the past researchers would have to find the nanotubes on the substrate and then make devices and circuits wherever they were," Mitra said. "But you want to be able to make things in parallel—at VLSI scale—without worrying about the exact placement and orientation of the nanotubes. We can now show that we are able to do that."

The research was funded by the Focus Center Research Program, a Semiconductor Research Corp. program, and the National Science Foundation.

####

For more information, please click here

Contacts:

Stanford News Service
425 Santa Teresa St.
Stanford, CA 94305-2245

(650) 723-2558 (main number)
(650) 725-0247 (fax)

Copyright © Stanford University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Shaping the Future of Nanocrystals: Berkeley Lab Researchers Obtain First Direct Observation of Facet Formation in Nanocubes August 21st, 2014

Hiden Release New Gas Analysis Catalogue August 21st, 2014

Wyatt Technology’s 24th International Light Scattering Colloquium to Highlight Developments in Applications and Characterization of Nanoparticles August 21st, 2014

Water window imaging opportunity: A new theoretical study elucidates mechanisms that could help in producing coherent radiations, ultimately promoting high-contrast imaging of biological samples August 21st, 2014

Chip Technology

Electrical engineers take major step toward photonic circuits: Team invents non-metallic metamaterial that enables them to 'compress' and contain light August 19th, 2014

Promising Ferroelectric Materials Suffer From Unexpected Electric Polarizations: Brookhaven Lab scientists find surprising locked charge polarizations that impede performance in next-gen materials that could otherwise revolutionize data-driven devices August 18th, 2014

AI Technology (AIT) Introduces Novel High Temperature Large Area Underfill with Proven Stress Absorption August 15th, 2014

Iranian Scientists Stabilize Protein on Highly Stable Electrode Surface August 14th, 2014

Nanotubes/Buckyballs

Iranian Scientists Stabilize Protein on Highly Stable Electrode Surface August 14th, 2014

SouthWest NanoTechnologies Appoints Matteson-Ridolfi for U.S. Distribution of its SMW™ Specialty Multiwall Carbon Nanotubes August 13th, 2014

Immune cells get cancer-fighting boost from nanomaterials August 13th, 2014

SouthWest NanoTechnologies Inc. Announces $2.7 Million in New Financing to Fund Growth, Plant Expansion and Technical Personnel August 11th, 2014

Discoveries

Shaping the Future of Nanocrystals: Berkeley Lab Researchers Obtain First Direct Observation of Facet Formation in Nanocubes August 21st, 2014

Water window imaging opportunity: A new theoretical study elucidates mechanisms that could help in producing coherent radiations, ultimately promoting high-contrast imaging of biological samples August 21st, 2014

Nanotechnology Helps Production of Super Adsorbent Polymers August 21st, 2014

Rice physicist emerges as leader in quantum materials research: Nevidomskyy wins both NSF CAREER Award and Cottrell Scholar Award August 20th, 2014

Announcements

Wyatt Technology’s 24th International Light Scattering Colloquium to Highlight Developments in Applications and Characterization of Nanoparticles August 21st, 2014

Ultra-short pulse lasers & Positioning August 21st, 2014

Malvern’s Dr Alan Rawle talks TLAs in plenary lecture at Particulate Systems Analysis conference August 21st, 2014

Water window imaging opportunity: A new theoretical study elucidates mechanisms that could help in producing coherent radiations, ultimately promoting high-contrast imaging of biological samples August 21st, 2014

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More














ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE