As a result, rather than covering a roof with expensive solar cells (the semiconductor devices that transform sunlight into electricity), the cells only need to be around the edges of a flat glass panel. In addition, the focused light increases the electrical power obtained from each solar cell "by a factor of over 40," Baldo says.

Because the system is simple to manufacture, the team believes that it could be implemented within three years--even added onto existing solar-panel systems to increase their efficiency by 50 percent for minimal additional cost. That, in turn, would substantially reduce the cost of solar electricity.

• Fact sheet: MIT's solar concentrators

In addition to Baldo, the researchers involved are Michael Currie, Jon Mapel, and Timothy Heidel, all graduate students in the Department of Electrical Engineering and Computer Science, and Shalom Goffri, a postdoctoral associate in MIT's Research Laboratory of Electronics.

"Professor Baldo's project utilizes innovative design to achieve superior solar conversion without optical tracking," says Dr. Aravinda Kini, program manager in the Office of Basic Energy Sciences in the U.S. Department of Energy's Office of Science, a sponsor of the work. "This accomplishment demonstrates the critical importance of innovative basic research in bringing about revolutionary advances in solar energy utilization in a cost-effective manner."

Solar concentrators in use today "track the sun to generate high optical intensities, often by using large mobile mirrors that are expensive to deploy and maintain," Baldo and colleagues write in Science. Further, "solar cells at the focal point of the mirrors must be cooled, and the entire assembly wastes space around the perimeter to avoid shadowing neighboring concentrators."

The MIT solar concentrator involves a mixture of two or more dyes that is essentially painted onto a pane of glass or plastic. The dyes work together to absorb light across a range of wavelengths, which is then re-emitted at a different wavelength and transported across the pane to waiting solar cells at the edges.

In the 1970s, similar solar concentrators were developed by impregnating dyes in plastic. But the idea was abandoned because, among other things, not enough of the collected light could reach the edges of the concentrator. Much of it was lost en route.

The MIT engineers, experts in optical techniques developed for lasers and organic light-emitting diodes, realized that perhaps those same advances could be applied to solar concentrators. The result? A mixture of dyes in specific ratios, applied only to the surface of the glass, that allows some level of control over light absorption and emission. "We made it so the light can travel a much longer distance," Mapel says. "We were able to substantially reduce light transport losses, resulting in a tenfold increase in the amount of power converted by the solar cells."

This work was also supported by the National Science Foundation. Baldo is also affiliated with MIT's Research Laboratory of Electronics, Microsystems Technology Laboratories, and Institute for Soldier Nanotechnologies.

Mapel, Currie and Goffri are starting a company, Covalent Solar, to develop and commercialize the new technology. Earlier this year Covalent Solar won two prizes in the MIT $100K Entrepreneurship Competition. The company placed first in the Energy category ($20,000) and won the Audience Judging Award ($10,000), voted on by all who attended the awards.

• Video: Marc Baldo discusses MIT's solar concentrator
• Article from MIT News website

"What we found is that we can make 'paper' from an interwoven mesh of nanowires that is able to selectively absorb hydrophobic liquids--oil-like liquids--from water," said Francesco Stellacci, an associate professor in the Department of Materials Science and Engineering and leader of the work.

In addition to its environmental applications, the nanowire paper could also impact filtering and the purification of water, said Jing Kong, an assistant professor of electrical engineering in the Department of Electrical Engineering and Computer Science and one of Stellacci's colleagues on the work. She noted that it could also be inexpensive to produce because the nanowires of which it is composed can be fabricated in larger quantities than other nanomaterials.

Stellacci explained that there are other materials that can absorb oils from water, "but their selectivity is not as high as ours." In other words, conventional materials still absorb some water, making them less efficient at capturing the contaminant.

The new material appears to be completely impervious to water. "Our material can be left in water a month or two, and when you take it out it's still dry," Stellacci said. "But at the same time, if that water contains some hydrophobic contaminants, they will get absorbed."

Made of potassium manganese oxide, the nanowires are stable at high temperatures. As a result, oil within a loaded membrane can be removed by heating above the boiling point of oil. The oil evaporates, and can be condensed back into a liquid. The membrane--and oil--can be used again.

Two key properties make the system work. First, the nanowires form a spaghetti-like mat with many tiny pores that make for good capillarity, or the ability to absorb liquids. Second, a water-repelling coating keeps water from penetrating into the membrane. Oil, however, isn't affected, and seeps into the membrane.

The membrane is created by the same general technique as its low-tech cousin, paper. "We make a suspension of nanowires, like a suspension of cellulose [the key component of paper], dry it on a non-sticking plate, and we get pretty much the same results," Stellacci said.

In a commentary accompanying the Nature Nanotechnology paper, Joerg Lahann of the University of Michigan concluded: "Stellacci and co-workers have provided an example of a nanomaterial that has been rationally designed to address a major environmental challenge."

In addition to Stellacci and Kong (who is also affiliated with MIT's Microsystems Technology Laboratory and Research Laboratory of Electronics, or RLE), other authors are Jikang Yuan, a postdoctoral associate in MIT's Department of Electrical Engineering and Computer Science (EECS) and RLE; Xiaogang Liu, now at the National University of Singapore; Ozge Akbulut of the Department of Materials Science and Engineering; Junqing Hu of the National Institute for Materials Science in Japan; and Steven L. Suib of the University of Connecticut, Storrs.

This work was primarily funded by the Deshpande Center for Technological Innovation at MIT.

- by Elizabeth A. Thomson, MIT News Office
May 30, 2008

A version of this article appeared in MIT Tech Talk on June 4, 2008 (download PDF).

"Professor Gibson brought a depth of experience, sound and thoughtful judgment, and a strategic perspective to this position, and I am deeply grateful for her service," Reif said. "I look forward to working with Professor Schmidt to build on the strong foundation she helped establish."

Professor Schmidt SM '83, PhD '88 has been a faculty member since 1988. From 1999 to 2006 he served as the director of the Microsystems Technology Laboratories (MTL) at MIT. His teaching and research is in the areas of micro and nanofabrication of sensors, actuators, and electronic devices, microelectromechanical systems (MEMS), design of micromechanical sensors and actuators, and micro/nanofabrication technology. He is the co-author of more than 60 archival journal publications and 110 peer-reviewed conference proceedings. His appointment will commence July 1.

The Associate Provost chairs the Committee for the Review of Space Planning (CRSP), with oversight for space planning, allocation and renovations across the Institute. The position also includes responsibility for managing faculty affairs, including faculty development, renewal, and grievance policies and procedures.

During her tenure as Associate Provost, Professor Gibson oversaw the David H. Koch Institute for Integrative Cancer Research from program development through to the beginning of construction. Working with Vice President for Human Resources Alison Alden and her staff, as well as the staff in the Provost's office, she also helped develop the recently announced program for faculty renewal. In addition, she chaired the Advisory Council on Neuroscience overseeing faculty searches.

From http://web.mit.edu/newsoffice/2008/assoc-provost-0606.html

The Faculty Early Career Development (CAREER) Program offers the NSF's most prestigious awards in support of the early career development activities of young faculty. The program is designed to recognize young scholars who demonstrate most effectively the integration of research and teaching within their organizations.

More information about the research activity in Prof. Dawson's group can be found at mtlweb.mit.edu/~jldawson.

LEES, an interdisciplinary research lab, provides the theoretical basis as well as the component, circuit and system technologies required to develop advanced electrical energy applications. Private financial support for the work that LEES performs is vital since much of the work that the lab does is at the forefront of innovation.

"This generous gift provides us the resources to initiate research into new areas and concepts that are not sufficiently developed to generate sponsored support," said LEES Director John Kassakian.

EECS Department Head Eric Grimson concurred. "At a time when traditional forms of financial support for this type of exciting research are disappearing, philanthropic gifts like these are especially critical to fulfilling MIT's mission to be at the cutting edge of both education and technology. We are deeply grateful to Dr. and Mrs. Landsman for their generosity."

A recognized expert in the field of power electronics, Emanuel Landsman formerly worked at Lincoln Laboratory, in the Space Communications Group and the Energy System Engineering Group. In 1981, he co-founded American Power Conversion Corp., a manufacturer of uninterruptible power supply products for computers and other electronic devices. Landsman has served as vice president and director of American Power Conversion since its inception. He is a recipient of the IEEE William E. Newell Award for Outstanding Achievement in Power Electronics.

A version of this article appeared in MIT Tech Talk on April 30, 2008 (download PDF).

Tomas Palacios' group at MTL uses wide bandgap semiconductors to revolutionize the fields of power electronics, ultra high frequency amplifiers and biosensors. More information about his research can be found on his group's website: http://web.mit.edu/tpalacios/

It's not that new treatments are needed--medical science long ago figured out how to cure tuberculosis using a cocktail of antibiotics. The problem is getting the medicine to the people who need it and, most difficult, making sure they follow the six-month regimen of daily doses.

Failure to follow the regimen not only leads to likely death of that patient, but fosters the development of antibiotic-resistant strains of the disease. "The problem is, how do you get people to take this complex regimen," says Manish Bhardwaj, a doctoral student in the Department of Electrical Engineering and Computer Science who works in the Microsystems Technology Laboratories.

After a year of hard work and about eight revisions, Bhardwaj and a team of collaborators think they may have found the answer. It's a high-tech solution in a simple, inexpensive and easy-to-use -package.

The first part of the two-component system is a kind of "smart" pillbox, called the uBox. It has 14 chambers that can each be loaded with several pills, which it dispenses from one chamber per day. To alert the patient that it's time to take the medicine, the box flashes its lights and sounds a buzzer. When the compartment is opened, the uBox records the exact time and prevents double-dosing by refusing to open again until the next treatment is due.

After two weeks, a health care worker reloads the box and digitally records and transmits the information stored in it. Doctors and public health services can then get complete data on compliance, patient by patient, in almost real time, instead of having to wait until the end of the six-month treatment.

"How do you know if pills are getting to the patients or if patients are taking them? Today, there's no good way of doing this," Bhardwaj says. If people fail to take all their pills, "it is possible to do harm by treatment that doesn't have good adherence." Missing medication can lead to the development of resistant strains, which can then be spread by that noncompliant patient. "The people they infect have no chance." Today, less than half of the patients that start the regimen successfully complete it..

"We want to make sure the worker is motivated," Bhardwaj says, and at present there's no way to tell which workers are diligent about making the calls and which ones may skip some of their appointed -visits. Accordingly, the uBox has an additional feature: a receptacle for a tiny key, like a headphone plug, which is carried by the visiting health care worker. At each visit the worker inserts the key, thus recording the fact that the patient really has been visited--another important gauge of compliance.

The second part of the group's new system is a cell phone, called the uPhone. By using special software, health care workers can record a patient's temperature, weight, and answers to a list of questions related to symptoms, which adds to the set of detailed patient data analyzed by doctors monitoring the study.

By looking at patterns of effects, the doctors can tell which field workers are achieving the best adherence rates with their patients and find out just what it is that those people are doing right. They can then be recruited to train additional workers.

Bhardwaj has been working with MIT alumni Goutam Reddy and Sara Cinnamon on the engineering and electronics of the pillbox, doctoral student Bill Thies and alumnus Pallavi Kaushik on the uPhone software, and MIT seniors Oliver Venn and Jessica Leon on fundraising and logistics.

Bhardwaj and Thiess went to Bihar province this January to begin their first field test of the product, conducting a training session for 22 workers who will, in turn, train the field workers to distribute the pillboxes in the field. In late April, Bhardwaj will return to Bihar to train workers an two new sites. The first actual field test with 100 of the boxes and 10 cell phones should start in mid-May.

If all goes well, a second round of testing, using 1,000 uBoxes, is set to begin. After that, it all depends on the results--and on the ability to raise funds for future deployment. Health officials in India are already keenly interested in this test, and Bhardwaj is about to meet with representatives of the Bill & Melinda Gates Foundation to discuss possible collaboration and support.

The Ven. Tenzin Priyadarshi, MIT's Buddhist chaplain, helped to get the project started and says, "I am hopeful that the uBox-uPhone project will revolutionize the way we understand and provide health care in rural areas of the world."

While Bhardwaj is proud of the product his team developed, he is not proprietary about it. "We hope to make the uBox and the uPhone the standard of treatment in Bihar. We worked very hard to make something very simple and elegant," he says. "But we'd be delighted if someone beats us to it and builds a uBox cheaper. We hope other people will copy us."

David Chandler, MIT News Office
February 6, 2008

From: http://web.mit.edu/newsoffice/2008/itw-india-tt0206.html

Metcalfe is most known for inventing Ethernet - he shares four patents on the local-area networking (LAN) standard - and for founding the billion-dollar networking company 3Com. In 2005, he received the nation's highest honor for technical innovation, the National Medal of Technology, for his leadership in the invention, standardization, and commercialization of Ethernet.

Today, Metcalfe is a venture capitalist at Polaris Venture Partners in Waltham, MA. He also serves on the boards of Polaris-backed companies, including Ember, SiCortex, Mintera, Infinite Power, SiOnyx, 1366, and GreenFuel, of which he is also Interim CEO.

Metcalfe graduated from MIT in 1969, with SB degrees in both industrial management and electrical engineering. He went on to receive an MS in applied mathematics (1970) and a PhD in computer science (1973) from Harvard.

The seminar is sponsored by the Microsystems Technology Laboratories (MTL) at MIT. MTL is an interdepartmental laboratory that supports Microsystems research encompassing work in circuits and systems, MEMS, electronic and photonic devices, and molecular and nanotechnology.

MTL Seminar Series Schedule:

All seminars take place at 50 Vassar Street, room 34-101, at 4PM.

March 4 - Bob Metcalfe, Polaris Venture Partners
March 11 - Emilio Bizzi, MIT Institute Professor
March 18 - Larry J. Hornbeck, Texas Instruments
April 1 - Donhee Ham, Harvard University
April 8 - Ali Hajimiri, California Institute of Technology
April 15 - Carl L. Hansen, University of British Columbia
April 29 - Kelin J. Kuhn, Intel Corporation
May 13 - TBA, MTL Doctoral Dissertation Seminar

The innovative design will be presented Feb. 5 at the International
Solid-State Circuits Conference in San Francisco by Joyce Kwong, a
graduate student in MIT's Department of Electrical Engineering and
Computer Science (EECS).

Kwong carried out the project with MIT colleagues Anantha
Chandrakasan, the Joseph F. and Nancy P. Keithley Professor of
Electrical Engineering, and EECS graduate students Yogesh Ramadass
and Naveen Verma. Their Texas Instruments (TI) collaborators are
Markus Koesler, Korbinian Huber and Hans Moormann. The team
demonstrated the ultra-low-power design techniques on TI's MSP430, a
widely used microcontroller. The work was conducted at the MIT
Microsystems Technology Laboratories, which Chandrakasan directs.

The key to the improvement in energy efficiency was to find ways of
making the circuits on the chip work at a voltage level much lower
than usual, Chandrakasan explains. While most current chips operate
at around one volt, the new design works at just 0.3 volts.

Reducing the operating voltage, however, is not as simple as it might
sound, because existing microchips have been optimized for many years
to operate at the higher standard-voltage level. "Memory and logic
circuits have to be redesigned to operate at very low power supply
voltages," Chandrakasan says.

One key to the new design, he says, was to build a high-efficiency DC-
to-DC converter-which reduces the voltage to the lower level-right on
the same chip, reducing the number of separate components. The
redesigned memory and logic, along with the DC-to-DC converter, are
all integrated to realize a complete system-on-a-chip solution.

One of the biggest problems the team had to overcome was the
variability that occurs in typical chip manufacturing. At lower
voltage levels, variations and imperfections in the silicon chip
become more problematic. "Designing the chip to minimize its
vulnerability to such variations is a big part of our strategy,"
Chandrakasan says.

So far the new chip is a proof of concept. Commercial applications
could become available "in five years, maybe even sooner, in a number
of exciting areas," Chandrakasan says. For example, portable and
implantable medical devices, portable communications devices and
networking devices could be based on such chips, and thus have
greatly increased operating times. There may also be a variety of
military applications in the production of tiny, self-contained
sensor networks that could be dispersed in a battlefield.

In some applications, such as implantable medical devices, the goal
is to make the power requirements so low that they could be powered
by "ambient energy," Chandrakasan says-using the body's own heat or
movement to provide all the needed power. In addition, the technology
could be suitable for body area networks or wirelessly enabled body
sensor networks.

"Together, TI and MIT have pioneered many advances that lower power
in electronic devices, and we are proud to be part of this
revolutionary, world-class university research," said Dr. Dennis
Buss, chief scientist at Texas Instruments. “These design techniques
show great potential for TI future low-power integrated circuit
products and applications including wireless terminals, battery-
operated instrumentation, sensor networks and medical electronics."

The research was funded in part by a grant from the U.S. Defense
Advanced Research Projects Agency.

- David Chandler, MIT News Office

We are now accepting nominations for the Third Annual Senturia Prize for Outstanding Thesis in Micro/Nanosystems. This prize is awarded yearly to a graduating doctoral student whose thesis has made outstanding contributions to their field. In addition to receiving an honorarium, the recipient will present a lecture on their research at the MNSS seminar on May 8, 2008.

Students, you are encouraged to nominate yourself. If you feel that your work has had significant impact in the field of micro/nanotechnology, please send an email to senturia-prize@mit.edu by March 7 with your thesis topic, primary advisor, a 1-pg description of your thesis contributions and significance, and your (expected) graduation date. We will solicit a recommendation from your thesis advisor.

Guidelines: This prize is open to doctoral students from the MIT micro/nano community who have recently graduated (since June 2007) or expect to graduate by August 2008. Selection will be based upon the strength & impact of the student's research, recommendations by advisors and/or committee members, and any contributions to the MIT MEMS/NEMS community. Nominations are due by Friday March 7. The prize winner will be announced by the end of March, and should be available to give the seminar on May 8.

Thank you!

Pat Doyle
Carol Livermore
Joel Voldman
Anne Wasserman
www.rle.mit.edu/mnss/

The researchers have taken the common techniques of gas chromatography and mass spectrometry and shrunk them to fit in a device the size of a computer mouse. Eventually, the team, led by MIT Professor Akintunde Ibitayo Akinwande, plans to build a detector about the size of a matchbox.

"Everything we're doing has been done on a macro scale. We are just scaling it down," said Akinwande, a professor of electrical engineering and computer science.

Akinwande and MIT research scientist Luis Velasquez-Garcia plan to present their work at the Micro Electro Mechanical Systems (MEMS) 2008 conference next week. In December, they presented at the International Electronic Devices Meeting.

Scaling down gas detectors makes them much easier to use in a real-world environment, where they could be dispersed in a building or outdoor area. Making the devices small also reduces the amount of power they consume and enhances their sensitivity to trace amounts of gases, Akinwande said.

He is leading an international team that includes scientists from the University of Cambridge, the University of Texas at Dallas, Clean Earth Technology and Raytheon, as well as MIT.

Their detector uses gas chromatography and mass spectrometry (GC-MS) to identify gas molecules by their telltale electronic signatures. Current versions of portable GC-MS machines, which take about 15 minutes to produce results, are around 40,000 cubic centimeters, about the size of a full paper grocery bag, and use 10,000 joules of energy.

The new, smaller version consumes about four joules and produces results in about four seconds.

The device, which the researchers plan to have completed within two years, could be used to help protect water supplies or for medical diagnostics, as well as detecting hazardous gases in the air.

The analyzer works by breaking gas molecules into ionized fragments, which can be detected by their specific charge (ratio of charge to molecular weight).

Gas molecules are broken apart either by stripping electrons off the molecules, or by bombarding them with electrons stripped from carbon nanotubes. The fragments are then sent through a long, narrow electric field. At the end of the field, the ions' charges are converted to voltage and measured by an electrometer, yielding the molecules' distinctive electronic signature.

Shrinking the device greatly reduces the energy needed to power it, in part because much of the energy is dedicated to creating a vacuum in the chamber where the electric field is located.

Another advantage of the small size is that smaller systems can be precisely built using microfabrication. Also, batch-fabrication will allow the detectors to be produced inexpensively.

The research, which started three years ago, is funded by the Defense Advanced Research Projects Agency and the U.S. Army Soldier Systems Center in Natick, Mass.

- Written by Anne Trafton, MIT News Office

Akinwande was cited for "contributions to the development of digital self-aligned gate technology and vacuum microelectronic devices," and Hoyt was commended for "contributions to silicon-based heterostructure devices and technology."

Further details on the FFA Program can be obtained at:
http://mtlweb.mit.edu/services/fabrication/ffa.html

At present, several companies are FFA members and have found this model of interaction with MTL to be highly successful. Pixtronix is one of the most active current FFA companies using the MTL fabs.

Pixtronix is an emerging display company developing portable displays optimized specifically for mobile multimedia devices. The company's revolutionary DMS™ (Digital Micro Shutter™) display technology utilizes micro-electrical-mechanical systems (MEMS) to achieve levels of video image quality and power efficiency never before seen in a display. Pixtronix MEMS technology development is conducted at several clean room facilities, including MIT's Microsystems Technology Laboratories (MTL). The company's ties to MIT and MTL's flexible FFA program have been instrumental in achieving accelerated design cycles and process development. Pixtronix is located in Andover, Mass., and is funded by Atlas Venture, Kleiner Perkins Caufield and Byers, DAG Ventures, Gold Hill Capital and GF Private Equity Group. For additional information, visit Pixtronix at www.pixtronix.com.

Charlie Sodini received his Bachelor of Science Degree in Electrical Engineering and a Bachelor of Arts Degree in Sociology from Purdue University in 1974. After graduating from Purdue, Charlie was a Technical Staff Member, and later Project Leader, at Hewlett Packard Labs. While at HP, Sodini continued his studies and was awarded his Master of Science Degree in Electrical Engineering (1981) and Ph.D. (1982) from the University of California, Berkeley. He was appointed to our faculty in 1983, and promoted to Full Professor in 1992. Charlie's research interests are in electronics and integrated circuit design and technology. More specifically, his research concerns technology intensive integrated circuit and systems design, with application toward sensory interface electronics and wireless communication emphasizing analog signal processing and RF integrated circuits. He has published extensively in these areas, and is co-author with Roger Howe of the textbook Microelectronics: An Integrated Approach.

Charlie has been very visible in professional leadership, having served as President of the IEEE Solid-State Circuit Society, as well
as General Chair of the IEEE VLSI Circuits Symposium and the International Electron Devices Meeting. He has also been involved in commercialization activities, co-founding SMaL Camera Technologies, which develops digital imaging solutions for a variety of business and consumer markets, including ultra-slim digital still cameras, automotive vision systems, and camera-enabled mobile devices (such as cell phones). Charlie has won best paper awards from ISSCC and the Darlington Award from the Circuits and Systems Society. He was elected a Fellow of the IEEE in 1995 for contributions to the development of over sampled A/D converters, DRAM devices and circuits,
and integrated circuits process technology.

Those variations can cause fluctuations in circuit speed and power so the chips don't meet their original design specifications, says MIT Professor Duane Boning, whose research team is working to predict the variation in circuit performance and maximize the number of chips working within the specifications.

The researchers have recently developed a model to characterize the variation in one kind of chip. The model could be used to estimate the ability to manufacture a circuit early in the development stages, helping to optimize chip designs and reduce costs.

"We're getting closer and closer to some of the limits on size, and variations are increasing in importance," says Boning, a professor of electrical engineering and computer science (EECS) and associate head of the department. "It's becoming much more difficult to reduce variation in the manufacturing process, so we need to be able to deal with variation and compensate for it or correct it in the design."

Boning and EECS graduate student Daihyun Lim's model characterizes variation in radio frequency integrated circuits (RFICs), which are used in devices that transfer large amounts of data very rapidly, such as high-definition TV receivers.

The researchers published their results in two papers in February and June. They also presented a paper on the modeling of variation in integrated circuits at this year's International Symposium on Quality Electronic Design.

RFIC chips are essential in many of today's high-speed communication and imaging devices. Shrinking the size of a chip's transistors to extremely small dimensions (65 nanometers, or billionths of a meter), improves the speed and power consumption of the RFIC chips, but the small size also makes them more sensitive to small and inevitable variations produced during manufacturing.

"The extremely high speeds of these circuits make them very sensitive to both device and interconnect parameters," said Boning, who is also affiliated with MIT's Microsystems Technology Laboratories. "The circuit may still work, but with the nanometer-scale deviations in geometry, capacitance or other material properties of the interconnect, these carefully tuned circuits don't operate together at the speed they're supposed to achieve."

Every step of chip manufacturing can be a source of variation in performance, said Lim. One source that has become more pronounced as chips have shrunk is the length of transistor channels, which are imprinted on chips using lithography.

"Lithography of very small devices has its optical limitation in terms of resolution, so the variation of transistor channel length is inevitable in nano-scale lithography," said Lim.

The researchers' model looks at how variation affects three different properties of circuits--capacitance, resistance and transistor turn-on voltage. Those variations cannot be measured directly, so Lim took an indirect approach: He measured the speed of the chip's circuits under different amounts of applied current and then used a mathematical model to estimate the electrical parameters of the circuits.

To the researchers' surprise, they found correlations between some of the variations in each of the three properties, but not in others. For example, when capacitance was high, resistance was low. However, the transistor threshold voltage was nearly independent of the parasitic capacitance and resistance. The different degrees of correlation should be considered in the statistical simulation of the circuit performance during design for more accurate prediction of manufacturing yield, said Lim.

The research was funded by the MARCO/DARPA Focus Center Research Program's Interconnect Focus Center and Center for Circuits and Systems Solutions, and by IBM, National Semiconductor and Samsung Electronics.

- Patti Richards, MIT News Office