Tests Strength of Advanced Thin Films
micrograph of a nanoporous insulation film
after “wrinkling” with a new NIST
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challenge of determining whether thin films—some
no thicker than a single molecule—are strong enough
for a growing number of important technology jobs just
got easier and quicker. A team led by researchers at
the National Institute of Standards and Technology (NIST)
reported in the the August issue of Nature Materials
that they have developed an inexpensive testing
method for such measurements.
for evaluating all types and combinations of materials,
the new method measures and analyzes the strength and
stiffness of a thin-film sample in about 2 seconds,
as compared with several minutes for indentation and
other conventional approaches. In addition, the NIST-developed
technique accommodates high-throughput testing, so that
hundreds or even a few thousand systematically varying
samples can be tested in rapid succession.
testing could spur progress in a large variety of existing
and emerging technology areas that rely on thin-film
advances for improved performance or enhanced protection.
Examples include semiconductors, solar cells, fuel cells,
coatings, magnetic storage devices and prospective nanotechnology
new method entails mounting a postage-stamp-sized assortment
of incrementally varying thin films on a strip of silicone
rubber about the size of a Band-Aid. Placed on a custom-built
stage, the combination of sample array and soft substrate
then is stretched or compressed. At a critical point
of instability, a sample buckles, wrinkling like a piece
of corrugated cardboard.
beneath the stage, a laser beams through the sample
and a camera captures the scattered light. From the
resulting diffraction pattern, the buckling wavelength—or
distance between the peaks of adjacent wrinkles—is
determined. Through a series of mathematical calculations,
the buckling wavelength is related
to the strength of the material.
further information, see www.nist.gov/public_affairs/releases/thin_films.htm.
Bello, (301) 975-3776
Safer Way to Make Metal Nanospheres
surface defects that form during processing can reduce
the quality and yield of semiconductor devices, magnetic
storage media and other products. Inspection tools that
locate, identify and characterize surface defects based
upon how they reflect or scatter light need to be calibrated
with accurate particle size standards in order to work
properly. Making metallic standards for such calibrations
is typically a hazardous process, but researchers at
the National Institute of Standards and Technology (NIST)
and the University of Maryland have invented a safer
method and apparatus for producing these standards.
Nanoscale spheres typically are used as size standards
for calibrating surface inspection instruments. NIST
produces a number of Standard Reference Materials (SRMs)
used by the semiconductor industry for calibration purposes,
including SRM 1963, which consists of 100 nanometer
(nm) polystyrene spheres. The new method produces uniformly
sized metal nanospheres, which might be used to determine,
for example, whether surface inspection systems can
differentiate metal contaminants from other defects.
new method, patented earlier this year and licensed
through the University of Maryland to MSP Corp., makes
spheres 50 nm to 300 nm in diameter out of copper, nickel,
cobalt and other metals. The method involves generating
aerosol droplets of a solution in an inert gas and heating
the droplets to form metal particles. The solution contains
a metal compound, water, and a solvent such as methanol
or ethanol. By contrast, the best of current production
technologies use hydrogen gas as the solvent, posing
a risk of fire or explosion.
ownership in the patent is also available for licensing.
Inquiries should be directed to Terry Lynch, (301) 975-02691or
further information, see www.nist.gov/public_affairs/factsheet/semiconwest04.htm.
Ost, (301) 975-4034
Standards to Improve Measurements of Microdevices
at the National Institute of Standards and Technology
(NIST), along with their colleagues at several companies,
are completing experiments that validate new standards
aimed at improving emerging new microelectromechanical
systems, or MEMS, devices.
Microaccelerometers, the devices used to activate automotive
airbags, are MEMS devices. In the future, microscopic
MEMs devices made with gears and motors may, for example,
be developed to clear blockages in arteries.
scientists presented their findings at the semiconductor
industry’s annual SEMICON West trade show, held
July 12-16, 2004, in San Francisco.
with ASTM International, NIST has developed three new
standards aimed at helping researchers measure more
accurately several characteristics of materials used
to construct MEMS devices. With more accurate measurements
of microsystem materials, designers and manufacturers
hope to improve the design and performance of these
devices. Currently, laboratories measuring the properties
of similar device materials produce widely varying results.
new standard is a set of procedures for measuring dimensions
or a particular materials property. One standard advances
the “in-plane length” measurement of a microsystem,
or its length in one dimension, typically from 25 micrometers
to 1,000 micrometers. A second standard would improve
measurement of “residual strain,” or the
strain the parts of a microsystem undergo before they
relax after the removal of the stiff oxides that surround
them during manufacturing. The final standard aims to
improve measurement of the “strain gradient,”
which determines the maximum distance that a MEMS component
can be suspended in air before it begins to bend or
companies have been collaborating with NIST on a so-called
“round robin” experiment to validate the
MEMS standards. The standards should significantly reduce
variations in measurements between laboratories.
Nance, (301) 975-5226