NIST Tech Beat - July 25, 2003

Editor’s Note: With the July 9, 2003 issue, we combined under one title two NIST newsletters, NIST Update and NIST TechBeat. We’ve made the change to help improve the timeliness of our topics. Our goal is to include newsworthy topics tied to publication of peer-reviewed papers, conference presentations, and other timely “news hooks” as often as possible. We also will be including photos and graphics whenever possible.
We hope you like the new look! Please let me know if you have any comments or suggestions.

Standards To Help Manufacturers Measure Micromachine Properties

When a car collides with another car, a tiny device called an accelerometer detects the change in motion and sets off an air bag, an innovation that has saved many lives.

The accelerometer is one of the most common uses of microelectromechanical systems (MEMS), but scientists and engineers also are starting to use them in devices ranging from angioplasty pressure sensors and pacemakers to optical disk drives.

MEMS, also known as micromachines, are a relatively new technology that uses existing microelectronics manufacturing methods to create complex machines with micrometer feature sizes. MEMS devices represent a rapidly growing component of the semiconductor industry. Many micromachines contain moving parts that are combined with integrated circuits. Like most high-tech devices, they must be made with precise dimensions and materials properties to operate properly. To help manufacturers ensure that their devices meet these exacting specifications, National Institute of Standards and Technology scientists and engineers helped develop three ASTM International standard test methods for the thin films used to make micromachines.

The test procedures, which are the first such standards in the world, will be published in The Annual Book of ASTM International Standards this month. The standards are expected to facilitate global commerce in MEMS technologies by enabling measurements that will lead to the development of more reliable and reproducible MEMS devices. The three standards provide detailed instructions for measuring thin-film dimensions and "strain," a property related to the stress in the thin film. NIST researchers have created a Web site to help semiconductor manufacturers perform the complex mathematical calculations required by the new standard test methods. For further information, see www.eeel.nist.gov/812/test-structures.

'Liquid Lenses' May Shrink Feature Sizes on Microchips

New data from the National Institute of Standards and Technology (NIST) will assist in the design of optics for liquid immersion lithography, an old idea that recently has attracted new interest as a possible means of improving image resolution and thereby shrinking feature sizes of computer chips.

Conventional optical lithography has advanced sufficiently to achieve a resolution of 100 nanometers (billionths of a meter), but there are physical and technical limits to how much better it can get. By placing certain liquids between the final optical element and the silicon wafer, it may be possible to extend the resolution to 65 nanometers for state-of-the-art lithography using the 193-nanometer wavelength of light, or even 45 nanometers or below for future systems using the 157-nanometer wavelength.

A key characteristic of liquids to be used in immersion lithography is their refractive index, which affects how light bends as it crosses an interface, such as that between the liquid and a lens or a silicon wafer. Air has an index close to one. By contrast, water has a refractive index almost 50 percent higher. Placing this higher-index fluid between the lens and the silicon wafer reduces the resolution-limiting effects of diffraction, enabling imaging of smaller feature sizes.

NIST physicists recently presented preliminary measurements of the refractive index for high-purity water, considered the best candidate for a "liquid lens" at the 193-nanometer wavelength. They also determined that the index is very sensitive to temperature changes, a critical issue for optics design. A forthcoming paper describes the techniques used to make these technically difficult measurements.* Future work will focus on refining these measurements and collecting data on other liquids that may be useful in 157-nanometer lithography.

*Burnett, John H., and Simon Kaplan. In press. "Measurement of the refractive index and thermooptic coefficient of water near 193 nanometers." To appear in Proceedings of SPIE Optical Microlithography XVI (2003) 5040-188.0

Media Contact:
Laura Ost, (301) 975-4034

Conference to Highlight Biometric Technologies

Automated methods of recognizing a person based on physiological or behavioral characteristics are expected to play an increasing role in arenas ranging from international border management to airport security. These biometric systems use technologies such as fingerprint matching, face recognition or iris identification.

To showcase recent advances in the field and examine technological and security issues facing the biometrics industry, the Biometrics Consortium Conference 2003 will be held Sept. 22-24, 2003, in Arlington, Va. The conference is sponsored by the National Institute of Standards and Technology (NIST), along with seven other federal, state and non-profit agencies that form the consortium.

Speakers will include executives from the biometrics industry, university researchers and representatives of federal agencies such as NIST, the National Security Agency and the Department of Homeland Security.

The conference will include a special session on research that will address topics such as the societal and political implications of deploying biometric systems, ways to measure effectiveness of various technologies and the challenges raised by countermeasures and spoofing. Other topics will include how biometric systems are starting to be deployed in some elementary and high schools, the role of biometrics in enhancing homeland security and transportation security, real world applications, interoperability, privacy, testing and evaluation, and security.

More than 70 biometric technology exhibits will be included at the conference, which will be held at the Hyatt Regency Crystal City.
For conference information and to register online, go to www.nist.gov/bc2003. Due to increased security at federal conferences, attendees must register in advance and produce photo identification to be admitted.

Standard Puts High-Speed Chips On the Fast Track

A new type of standard to be issued by the National Institute of Standards and Technology (NIST) this summer will help meet the need for speed in semiconductors.

The "interactive reference material" is designed to help users calibrate instruments that determine the germanium fraction in silicon-germanium thin films, now used in the conducting channels of high-speed semiconductors for computers. By measuring the composition of the standard material and comparing their results to NIST's values as part of the instrument calibration process, users can reduce measurement uncertainty and optimize thin film compositions with just the right amount of germanium. Germanium causes strain in the silicon lattice, allowing electrons to move faster and thereby increasing device operating speed as much as twofold.

The new standard—which consists of sets of thin films of varying compositions—is among the first to be developed through interactions between industrial participants, who supply and characterize the materials, and NIST staff, who coordinate the process, conduct additional measurements and tests, and assign values. The process is less rigorous than the traditional Standard Reference Material (SRM) approach and may not result in certified values. But interactive materials can be made available relatively quickly, just 1 to 2 years after a need is identified, compared to about 5 years for a new SRM.

The need for the silicon-germanium standard was identified at an industry workshop 2 years ago. The uncertainty of compositional measurements currently is limited by available analytical tools to about 5 percent; the new standard has been measured with an uncertainty of about 1 percent.

Fire Investigative Team Describes Progress

It's been five months since the February 2003 fire at The Station nightclub in West Warwick, R.I., left 100 dead and some 200 others injured. Many questions have arisen in the tragedy's aftermath about the behavior of the smoke and fire, the manner in which the nightclub was evacuated, and the most probable cause of the building's failure. NIST's ongoing technical investigation of the Rhode Island nightclub fire is making progress toward finding the answers that will lead to recommendations on how to improve the structural fire safety of similar buildings. A recent statement from the agency updates the status of the effort. The document, along with other information (including the complete investigation plan), may be found at www.nist.gov/ncst.

Quick Links

Baldrige Winners Share Tips: Senior leaders from organizations selected for the Malcolm Baldrige National Quality Award, including the first winners in health care and education, will share their best practices at conferences in Cincinnati, Ohio, on Sept. 23, and Scottsdale, Ariz., on Oct. 9. For more information and to register online, go to http://baldrige.nist.gov/2003_Regionals/Regionals.htm.