[Editors] MIT's Nanoruler could impact space physics, more

[Elizabeth Thomson]

MIT News Office
Massachusetts Institute of Technology
Room 11-400
77 Massachusetts Avenue
Cambridge, MA  02139-4307
Phone: 617-253-2700
http://web.mit.edu/newsoffice/www

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MIT's Nanoruler could impact space physics, more
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For Immediate Release
MONDAY, FEB. 2, 2004
Contact: Elizabeth A. Thomson, MIT News Office
Phone: 617-258-5402
Email: thomson at mit.edu

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CAMBRIDGE, Mass.--An MIT device that makes the world's most precise 
rulers-with "ticks" only a few hundred billionths of a meter 
apart-could impact fields from the manufacture of computer chips to 
space physics.

The Nanoruler is 10 to 1,000 times faster and more precise than other 
methods for patterning parallel lines and spaces (known collectively 
as gratings) across large surfaces more than 12 inches in diameter. 
Such large surfaces are key to a number of applications involving 
gratings, such as larger wafers for the production of computer chips 
and higher-resolution space telescopes.

"Patterning gratings with precise control across large areas has 
bedeviled labs around the world for a long time, despite great 
efforts," said Mark L. Schattenburg (Ph.D. 1984), leader of the team 
and director of MIT's Space Nanotechnology Laboratory in the Center 
for Space Research (CSR).

The Nanoruler can pattern gratings of lines and spaces separated by 
only a few hundred nanometers, or billionths of a meter, across a 
surface 300 millimeters in diameter. It does so with a precision of 
less than one nanometer. "That is the equivalent of shooting a target 
the size of a nickel in Manhattan all the way from San Francisco," 
said Carl G. Chen (Ph.D. 2003), one of Schattenburg's colleagues.

The researchers reported the results of initial trials of the 
Nanoruler in the November-December issue of the Journal of Vacuum 
Science and Technology B. In addition to Schattenburg and Chen, they 
include Paul T. Konkola (Ph.D. 2003) and CSR research scientist Ralf 
K. Heilmann. The team also received significant technical assistance 
from Robert Fleming of the CSR sponsored research technical staff.

The Nanoruler continues a line of research in advanced grating 
fabrication technology initiated at MIT in the late 1940s. Gratings 
are of particular interest to scientists and engineers because, among 
other things, they allow the analysis of light.

When the distance between one line and its neighbor, or period, is 
comparable to the wavelength of light, a phenomenon called 
diffraction occurs. Essentially the grating spreads the light into a 
spectrum, much as a prism spreads light into its colors. That 
spectrum, in turn, can be analyzed for information about the source.

For example, one such grating is key to NASA's Chandra X-ray 
Observatory. The High Energy Transmission Grating, also developed by 
Schattenburg's lab at MIT, spreads the X-rays from Chandra's mirrors 
into a spectrum that can then be "read" like a kind of cosmic bar 
code. From there, scientists can deduce the chemical composition and 
temperature of the source (such as the corona of a star).

BUILDING A BETTER RULER

Schattenburg began the Nanoruler project because he wanted to create 
a better ruler for the semiconductor industry. "Today's advanced 
computer chips are packed with millions of transistors," he said. 
"Increasingly, however, it becomes a challenge to stuff more and more 
of these ever-shrinking features into an area no larger than a 
thumbnail."

What Schattenburg wanted, in essence, was an extremely well-made 
ruler whose ticks are spaced not millimeters but nanometers apart, 
and whose size was comparable to the largest commercial silicon 
wafers. "If such a ruler could be created, it would help chip makers 
do a much better job of laying down the Lilliputian circuitry," he 
said.

The Nanoruler does the trick by combining two conventional methods to 
create gratings: mechanical ruling and interference lithography. 
Mechanical ruling essentially involves dragging a very sharp 
tool-almost always a diamond point-across the surface to form the 
sets of lines and spaces. Among other drawbacks, however, it is 
time-consuming.

In interference lithography, two beams of light interfere with each 
other to produce interference "fringes," or parallel planes of high 
and low light intensity. These fringes can then be recorded in the 
surface as lines and spaces, using the same techniques common to the 
patterning of miniscule designs on computer chips. Interference 
lithography is much faster than mechanical ruling since all the 
grooves are formed simultaneously in a single exposure.

The Nanoruler essentially moves the surface to be patterned on a 
stage as a laser creates the interference fringes that in turn become 
the lines and spaces. "While other tools can make gratings with 
smaller periods, none is as fast or as accurate as the Nanoruler," 
Schattenburg said.
The project, which took five years, has had its share of trials and 
tribulations, Chen recalls. For example, toward the end he was stuck 
in Beijing for six months due to a visa delay. During that time he 
was able to work out some of the fundamental physics validating the 
Nanoruler concept.

"The experience of building the Nanoruler from scratch has been 
immensely rewarding," he concluded.

NASA and DARPA sponsored the research. The Nanoruler is 
patent-pending. For more information, go to http://snl.mit.edu.

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