Directed self-assembly grabs the spotlight at SPIE

SAN JOSE, Calif.—If there is a darling of this year's SPIE Advanced Lithography conference, it just might be directed self-assembly, a technology that emerged in recent years to land on the International Technology Roadmap for Semiconductors (ITRS) and is considered a potential candidate to extend optical lithography.

More than 10 papers on the conference schedule are focused on directed self-assembly, a technology that combines lithographically defined substrates and self-assembled polymers. Research has focused on using lithography to alter the surface of a silicon wafer, then adding block co-polymers that assemble themselves into regular arrays along the defined pattern.

"This is a long-range lithography technology,'' said G. Dan Hutcheson, CEO of market research firm VLSI Technology Inc. Researchers see it as a potential path to the sub-10-nm range, Hutcheson said.

Directed self-assembly first landed on the ITRS in 2007 as a potential solution for leading-edge, critical layer lithography. The technology is still part of the ITRS as of the 2009 edition.

"We are still there [on the 2009 ITRS], though numerous and daunting challenges remain," said Paul Nealey, Smith-Bascom professor of chemical and biological engineering for the Nanoscale Science and Engineering Center at the University of Wisconsin-Madison.

In a presentation at SPIE Tuesday (Feb. 23), Nealey said directed self-assembly is not competing with nano-imprint or interference lithography, two other promising alternative lithography technologies. Nealey added that he thinks that all three technologies will be needed in years to come.

But despite its prominence at SPIE and its inclusion on the ITRS, directed self-assembly is clearly a technology still in development.

Nealey and his team are working on fabricating a nano-wire array that can serve as a platform to help them study the effectiveness of their implementation of the technology. "We're close," Nealey said.

Nealey also said researchers are developing models that are on the verge of becoming predictive—nearing the stage where they can surmise what polymers will form at what boundary predictions.

"I think we are very close to having things that could be usable in the near future," said William D. Hinsberg of IBM's Almaden Research Center, in another paper presentation Tuesday. Hinsberg added that directed self-assembly "is not and never will be a drop-in replacement for lithography."

Both Nealey and Hinsberg appealed to materials engineers to keep working.

"There is a lot of polymer engineering that can be done on the design of block co-polymer materials that want to make the shapes of integrated circuit elements," Nealey said.

Hinsberg said that improved materials, including block co-polymers and surface control layers "will be critical to moving forward in the future."