[Editors] MIT reports finer lines for microchips

[Elizabeth Thomson]

For Immediate Release
TUESDAY, JUL. 8, 2008

Contact: Elizabeth A. Thomson, MIT News Office
T. 617-258-5402   E.: thomson at mit.edu

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MIT reports finer lines for microchips

-- Advance could lead to next-generation computer chips, solar cells,  
more
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PHOTO AVAILABLE

CAMBRIDGE, Mass.—MIT researchers have achieved a significant advance  
in nanoscale lithographic technology, used in the manufacture of  
computer chips and other electronic devices, to make finer patterns  
of lines over larger areas than have been possible with other methods.

Their new technique could pave the way for next-generation computer  
memory and integrated-circuit chips, as well as advanced solar cells  
and other devices.

The team has created lines about 25 nanometers (billionths of a  
meter) wide separated by 25 nm spaces. For comparison, the most  
advanced commercially available computer chips today have a minimum  
feature size of 65 nm. Intel recently announced that it will start  
manufacturing at the 32 nm minimum line-width scale in 2009, and the  
industry roadmap calls for 25 nm features in the 2013-2015 time frame.

The MIT technique could also be economically attractive because it  
works without the chemically amplified resists, immersion lithography  
techniques and expensive lithography tools that are widely considered  
essential to work at this scale with optical lithography. Periodic  
patterns at the nanoscale, while having many important scientific and  
commercial applications, are notoriously difficult to produce with  
low cost and high yield. The new method could make possible the  
commercialization of many new nanotechnology inventions that have  
languished in laboratories due to the lack of a viable manufacturing  
method.

The MIT team includes Mark Schattenburg and Ralf Heilmann of the MIT  
Kavli Institute of Astrophysics and Space Research and graduate  
students Chih-Hao Chang and Yong Zhao of the Department of Mechanical  
Engineering. Their results have been accepted for publication in the  
journal Optics Letters and were recently presented at the 52nd  
International Conference on Electron, Ion and Photon Beam Technology  
and Nanofabrication in Portland, Ore.

Schattenburg and colleagues used a technique known as interference  
lithography (IL) to generate the patterns, but they did so using a  
tool called the nanoruler—built by MIT graduate students—that is  
designed to perform a particularly high precision variant of IL  
called scanning-beam interference lithography, or SBIL. This recently  
developed technique uses 100 MHz sound waves, controlled by custom  
high-speed electronics, to diffract and frequency-shift the laser  
light, resulting in rapid patterning of large areas with  
unprecedented control over feature geometry.

While IL has been around for a long time, the SBIL technique has  
enabled, for the first time, the precise and repeatable pattern  
registration and overlay over large areas, thanks to a new high- 
precision phase detection algorithm developed by Zhao and a novel  
image reversal process developed by Chang.

According to Schattenburg, “What we’re finding is that control of the  
lithographic imaging process is no longer the limiting step. Material  
issues such as line sidewall roughness are now a major barrier to  
still-finer length scales. However, there are several new  
technologies on the horizon that have the potential for alleviating  
these problems. These results demonstrate that there’s still a lot of  
room left for scale shrinkage in optical lithography. We don’t see  
any insurmountable roadblocks just yet.”

The MIT team performed the research in the Space Nanotechnology  
Laboratory of the MIT Kavli Institute of Astrophysics and Space  
Research, with financial support from NASA and NSF.

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Written by David Chandler, MIT News Office