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Nanoscopic ''ruler'' could provide microchip benchmark.
18:14 25 February
2005
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The magnified section shows lattice lines just 0.3 nanometres apart on a block measuring 40 nm x 275 nm (Image: NIST)
A
nanoscopic measuring device that uses atomic lattices to gauge tiny
distances could enable microelectronics engineers to build better
components, say US scientists.
The
"nanoruler" was developed by
researchers at the US government''s
National Institute of Standards and Technology (NIST) in Maryland, and
industry collaborators. They say it will enable researchers and
engineers working on nanoscale objects to calibrate their instruments
more precisely, resulting in greater accuracy in their work.
To
construct the instrument, NIST researcher Michael Cresswell says the
team exploited the way in which silicon atoms align themselves into
uniform lattice structures. They had to etch the raw silicon in the
correct orientation to ensure the lattices were perpendicular to the
top and bottom surfaces. If not, the distance between each lattice
would not be standard.
The
nanoscopic slab can provide precise measurements by counting the number
of silicon lattice lines crossed by an object. An advantage silicon is
that the width of each atomic lattice is known to within about
one-tenth of a nanometre, says Cresswell, at 0.3 nanometres.
Nanorulers
varying in size from 40 to 275 nanometres can be constructed. These
could, for example, be used by nano-engineers to improve the
calibration of instruments such as atomic force
microscopes, scanning
tunnelling microscopes and electron microscopes.
Especially useful
Researchers
currently use a variety of materials to calibrate their instruments,
the best of which is still seven times less accurate than the silicon
ruler, Cresswell told New Scientist. He adds that the nanoruler
could prove especially useful in microelectronics fabrication, where
engineers check the dimensions of components after each step of their
work.
Peter
Hatto, chairman of the European Committee for Standardization''s working
group on nanotechnology, says a precise standard for nano-measuring
would be a very useful research tool.
"You
really need to use a fundamental measurement standard but you can''t use
the metre without an artefact to calibrate against," he says. The NIST
nanoruler has the advantage that the properties of silicon are already
well understood, he adds.But Hatto also notes that it will be crucial
to provide researchers with easy access to the material to ensure it is
used.
The
ruler was developed by NIST in collaboration with three US companies;
Sematech, in Texas, US, and VLSI Standards and Accurel, both based in
California, US.