Researchers Explore Copper Replacements In Chips

As consumer demand grows for smaller and faster chips, copper interconnects become more difficult and costly to fabricate; one partnership is exploring the use of nanotubes instead.
SAN JOSE, Calif. — Arrowhead Research Corp. and Duke University on Friday (Nov. 4) announced plans to research and develop carbon nanotube-based interconnects as a possible replacement for copper in computer chips.

Arrowhead, a nanotechnology company, will also work with Jie Liu, a nanotube expert at Duke. Arrowhead (Pasadena, Calif.) has agreed to provide approximately $680,000 in funding over the next two years to develop Liu's technology.

In exchange, Arrowhead will have the exclusive right to license the resulting intellectual property and commercialize the process developed at Duke. Duke University is developing what it calls a single-walled nanotube (SWNTs) synthesis process.

“We developed an improved CVD method for preparing SWNTs with high catalyst productivity. The total amount of high quality SWNTs produced is greater than 200 percent the weight of the catalysts. The materials made using the method are of high quality as characterized by SEM and TEM,” according to Duke University.

The diameter of the resulting SWNTs ranges from 0.7- to 1.5-nm, with a standard deviation of 17 percent, according to the university.

"There is a burning need in the semiconductor industry for a new material to replace copper interconnects,” said R. Bruce Stewart, Arrowhead's president, in a statement. "Our intention is to fund development of a CMOS-compatible process at Duke over the next two years, and then partner with device manufacturers to integrate carbon nanotube-based interconnects into their manufacturing processes."

As consumer demand grows for smaller and faster chips, copper interconnects become more difficult and costly to fabricate. Also, copper's structural and electrical properties intrinsically degrade at smaller scales, according to Arrowhead.

A phenomenon known as electromigration threatens the reliability of nanometer-size copper interconnects. Electromigration causes internal and external cavities that lead to wire failure.

Copper burns out at one million amps per square centimeter while nanotubes can carry up to a billion amps per square centimeter. Bundles of densely packed nanotubes can also have substantially lower resistance than copper.

Although several players in the semiconductor industry have identified nanotubes as a prime candidate to replace copper, substantial challenges remain in synthesizing the materials and integrating them into chips.

"To our knowledge, corporate research groups have encountered recurring problems in the manufacturing strategies they have pursued," said Stewart. "We believe Dr. Liu and his research team at Duke have a completely different approach that could enable large volume manufacturing of nanotube interconnects in future chips."

Editor's Choice
Cynthia Harvey, Freelance Journalist, InformationWeek
John Edwards, Technology Journalist & Author
Sara Peters, Editor-in-Chief, InformationWeek / Network Computing