Nanotechnology
is challenging the National Institute of Standards and Technology to downsize
its measurement tools, which the agency did recently by releasing the world's
first silicon nano-ruler. Designed for the semiconductor microchip
manufacturing industry, the silicon nano-ruler is a "calibrated
artifact" that is individually measured and certified by NIST for the
spacing, angles and orientation of its silicon atoms. The silicon nano-ruler
allows semiconductor manufacturers to accurately measure the thickness, crystal
structure, embedded strain and orientation of the atoms in modern semiconductor
devices.
"Our
customers for this are people who are developing advanced semiconductors,"
said NIST materials scientist Donald Windover. "They need our calibrated
artifacts in order to measure the new types of structures they are making."
Currently,
NIST offers about 1,300 reference materials for calibrating instruments in all
industries, including electronics, manufacturing, chemistry, environmental
monitoring, criminal forensics and dozens of other fields.
"For
over 30 years, the National Institute of Technology has supplied calibration
artifacts," said Windover "You measure the NIST specimen with your
instrument to find out how much offset there is between your tool and our
measurements, then you correct your tool."
About
10 years ago, NIST realized that semiconductor microchips were headed for the
nanoscale and started constructing a new instrument capable of making
measurements that fine. Called a parallel beam diffractometer, NIST now claims
it has the world's most accurate measuring device of its kind. The instrument,
which took a decade to construct, now allows NIST to calibrate any number of
silicon nano-rulers for distribution to semiconductor microchip manufacturers
who use it to calibrate their X-ray diffraction tools.
"We
need to prepare and do these things about a decade in the future," said
Windover, "because it takes that long to eliminate all the uncertainties
in our measurements."
The
new silicon nano-ruler (priced at $1,506) is the first of a new family of
calibration artifacts that NIST wants to offer to the burgeoning manufacturers
of semiconductor microchips. Officially called Standard Reference Material 2000
(SRM-2000), each silicon nano-ruler is certified by NIST to have uncertainties
of under a femtometer—that's a million times smaller than your typical
atom—about the size of a neutron. Angles are measured with an accuracy of
better than an arc second, that's 1/3,600 of a degree, or the angle made by a
quarter when viewed from two miles away.
Other
members of the growing family will include a new set of standard reference
materials to measure the coatings used to pattern circuitry atop silicon
wafers, including thin films, epitaxial structures and the self-assembled
monolayers used to craft atomic scale features.
