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Semiconductors
Promising
Strategy May Help Overcome Measurement Dilemma
As
the features of electronic circuits continue to shrink,
it becomes increasingly difficult to accurately measure
their widths because images of object edges are inherently
fuzzy at extreme magnification. No microscope is perfect,
so images always contain distortions at some level, and
width measurements are particularly sensitive to these.
With mathematical models of the instruments, the distortions
can be corrected.
But
how accurate are the models? The answer can be found only
by testing the models with a sample for which the exact
width is known. Unfortunately, there are no such samples;
the inherent image fuzziness makes them hard to come by.
Now,
researchers at NIST have
taken a major step in solving that problem. Their solution
is to make a sample that can be measured by different instruments
that operate on completely different principles. Then, the
image distortion is corrected with models developed at NIST
(and in some cases, now commercially available). The better
the results agree, the less likely that significant model
errors exist.
NIST
scientists have successfully measured a silicon sample with
three types of measurement techniques: scanning electron
microscopy, atomic force microscopy and a method called
electrical critical dimension (or ECD) measurement, which
determines the width of a feature by analyzing its electrical
resistance.
The
uncertainties for the first two instruments were a mere
5 and 13 nanometers, respectively. The electrical measurement
technique yielded a higher uncertainty of 34 nanometers,
possibly because the sample's low electrical conductivity
made it less than optimal for this type of measurement.
The next step will be to measure a sample with higher conductivity
so that the ECD can be better measured.
For
technical information, contact John
Villarrubia, NIST, 100 Bureau Dr., Stop 8212, Gaithersburg,
Md. 20899-8212; (301) 975-3958.
Media
Contact:
Michael E. Newman, (301) 975-3025 
Optoelectronics
Spare
the Rod, Spoil the Accuracy for Fiber Measurements
Three
standard reference materials relating to the diameter of
coated optical fibers are available for sale through the
NIST
Standard Reference Materials Program. They were developed
jointly by the NIST
Optoelectronics and Precision Engineering Divisions.
These SRMs are intended primarily for use in calibrating
instruments that measure the diameter of coated optical
fibers. Each SRM unit--consisting of an uncoated glass rod
approximately 100 millimeters long and 250 micrometers in
diameter--is individually certified for index of refraction
and diameter. The index of refraction of the glass rod was
chosen to match that of certain fiber coatings. Three indexes
are available: 1.504 (SRM 2553), 1.515 (SRM 2554) and 1.535
(SRM 2555). Each rod is marked with a glued-on tab to assist
in proper angular orientation during measurement. This flag
also serves as the orientation reference for additional
certified measurements at the angular positions indicated
on the SRM certificate.
To
order one or more of the standards, contact the SRMP, NIST,
100 Bureau Dr., Stop 2320, Gaithersburg, Md. 20899-2320;
(301) 975-6776; fax: (301) 948-3730; srminfo@nist.gov.
Each SRM costs $363.
Media
Contact:
Fred McGehan (Boulder), (303) 497-3246
MEP
New
Report Charts Path to Transformation with MEP's Help
The
NIST Manufacturing Extension
Partnership has helped thousands of small manufacturers
solve problems and improve the way they do business. But,
some of MEP's clients not only have improved, they have
transformed into models of high-performing, world-class
enterprises.
For
example, Dynagear Oil Pumps, Inc., in Maquoketa, Iowa, was
losing profits and customers. Rumors that the company was
going bankrupt were causing low employee morale and even
lower productivity and product quality. After working with
the Iowa Manufacturing Technology Center, an affiliate of
the NIST MEP, Dynagear completely transformed its culture
and improved its business. Profits increased by 20 percent
in 1997 and by 65 percent in 1998. Wages have increased
by 16 percent over the past four years. Scrap rates have
been reduced by 61 percent and product rework by 50 percent.
The company has received several awards from key clients.
A
new MEP report documents seven transformed firms, including
Dynagear, describing the firm and its problems, the changes
that were made, and the results in performance. The report,
Transformed Firms Case Studies, can be obtained by
calling (800) MEP-4-MFG (637-4634).
This
report is the latest in a series of case studies on MEP's
client companies. Other reports are Exemplary Projects
Case Studies, Workforce Development Case Studies and MEP
Successes: A Case Study Approach.
The
NIST MEP is a nationwide network of manufacturing extension
centers helping smaller manufacturers in all 50 states,
the District of Columbia and Puerto Rico. Smaller manufacturers
can call the toll-free number listed above to reach the
MEP center serving their region or check out the MEP World
Wide Web site at www.mep.nist.gov.
Media
Contact:
Jan Kosko, (301) 975-2767
Materials
Researcher
Investigates Reliability Problems with Flip-Chips
In
an effort to make electronic circuit boards smaller, cheaper
and faster, the electronics industry has gone to flip-chip-on-board
technology. This means attaching silicon chips to printed
wiring boards with solderballs. Increased speed is achieved
by decreasing the distance between the chip and the substrate.
This technology works well at temperatures from 20 degrees
to 120 degrees Celsius but fails at an unacceptable rate
when temperatures are reduced to minus 55 degrees Celsius.
Seeking
the reason for the failure, Elizabeth S. Drexler of NIST's
Materials Reliability Division, Boulder, Colo., used
the electron-beam moire technique to study local deformations
in a flip-chip package and interactions among the various
materials found within the package. As temperatures changed,
images of the moire fringe patterns were acquired and compared.
The package was subjected to 10 complete thermal cycles
from minus 55 degrees Celsius to 125 degrees Celsius over
several days.
Drexler
found, after only one complete thermal cycle, that debonding
initiated between the solderball and the solder mask where
that interface meets the printed circuit board. This debonding
continued to grow through the solder mask and into the underfill,
then arrested after going one-quarter of the way around
the solderball. At the end of the 10 cycles, holes about
200 nanometers across were found at other locations where
the solderball/solder mask meets the printed circuit board.
However, the holes never coalesced to form a crack. Deformation
also was induced within the solderball, becoming more pronounced
with more thermal cycles.
For
a copy of two papers (listed as no. 17-99) discussing the
flip-chip problems, contact Sarabeth
Harris, MC 103, NIST, Boulder, Colo. 80303-3337; (303)
497-3237.
Media
Contact:
Fred McGehan (Boulder), (303) 497-3246
Electromagnetic Properties
Documents
Tell How to Improve Cavity Measurement Accuracy
The
air-filled stripline cavity is used widely in industrial
laboratories for measuring the dielectric and magnetic properties
of materials at RF/microwave frequencies. The results of
two recent NIST studies suggest that the measurement accuracy
of this technique is unsatisfactory. The reasons: less-than-optimal
perturbation of the internal cavity fields by the material
specimens under test, failure to correct for magnetic depolarization
errors (in complex permeability measurements only), and
excessive radiation losses during dielectric measurements
which create major errors in the estimation of losses.
Methods
of improving measurement accuracy are suggested, including
how to choose optimal specimen dimensions. The NIST studies
are documented in three recent publications: NIST Technical
Note 1505, Stripline Resonator for Electromagnetic Measurements
of Materials; Paper 8-99a, Permittivity and Permeability
Measurements Using Stripline Cavities--A Comparison; and
Paper 8-99b, On RF Material Characterization in the Stripline
Cavity.
All
three documents are available from Claude Weil, NIST, MC
813.01, Boulder, Colo. 80303-3337; (303) 497-5305; weil@boulder.nist.gov.
Media
Contact:
Collier Smith (Boulder), (303) 497-3198
Administration
Kovac
Named to NIST Visiting Committee; Goesser Resigns
NIST
Director Ray Kammer has named Caroline A. Kovac, vice president
of services, applications and solutions for the IBM Research
Division, to serve on the Visiting
Committee on Advanced Technology, the agency's primary
private-sector policy adviser. Kovac's three-year term expires
Jan. 31, 2002.
At
IBM, Kovac oversees about 650 scientists and engineers around
the world that develop innovative technologies in electronic
business, supply chain management, user interface, electronic
collaboration and other areas. Kovac's prior positions at
IBM include vice president of technical strategy and worldwide
operations for IBM Research, director of intelligent production
decision solutions for the IBM Manufacturing Industry Solution
Unit, and director of manufacturing research. She is a member
of the IBM Academy of Technology.
Kammer
also announced that Louise Goesser, formerly the general
manager, Refrigeration Product Team, North American Appliance
Region, at Whirlpool Corp., has resigned from the VCAT to
meet the demands of her new position as vice president,
Quality, at Ford Motor Co.
The
VCAT was established by Congress in 1988 to review and make
recommendations on NIST's policies, organization, budget
and programs. Its membership was increased from nine to
15 by the National Technology Transfer and Advancement Act
of 1995.
Media
Contact:
Michael E. Newman, (301) 975-3025
Awards
NIST
Scientist Receives Gold Medal for Refrigeration Work
At
its centenary meeting in London recently, the Institute
of Refrigeration awarded its J&E Hall Gold Medal to NIST's
Ray Radebaugh for his development of super-cold pulse tube
refrigerators.
"Dr.
Radebaugh's pioneering work on the development and theory
of pulse tube refrigerators has stimulated an intense worldwide
study of this new refrigeration method for many cryogenic
cooling applications," the citation states.
The
award is sponsored by J&E Hall Ltd., the world's oldest
refrigeration company.
Leader
of NIST's Cryogenic Technologies Group, Radebaugh long has
studied super-cold refrigerators and co-developed the first
cryogenic refrigerator with no moving parts. These refrigerators
are used to cool infrared instruments on civilian and military
satellites. They also are used to cool microwave filters
in cellular-phone base stations. Experiments now are under
way to use pulse tube refrigerators to liquefy natural gas
as a clean-burning fuel for fleet vehicles. They also may
have applications in making semiconductor chips.
In
addition to the gold medal--which he must return in a year--
Radebaugh received a silver medal to keep and a cash award
of $8,000.
Media
Contact:
Fred
McGehan, (303) 497-3246
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