individual electrons. At present, there is no fundamental representation of current; the standard for current is realized through the representations of voltage and resistance. An independent representation of current could provide significant additional confidence in the coherency of the realization of the SI (International System of Units) electrical units. This project is a good example of how NIST uses new technologies to update and enhance its capabilities in fundamental metrology.

In the Manufacturing Engineering Laboratory (MEL), the establishment of the X-ray Optics Calibration Interferometer (XCALIBIR) system provides NIST with best-in-the-world capability in optical figure metrology. The instrument is housed in a specially constructed, controlled-environment enclosure and will be used, among other purposes, for calibration of the very-high-precision optical components necessary for the Laser Interferometer Gravitational-wave Observatory (LIGO) and the Department of Energy National Ignition Facility (NIF).

The Building and Fire Research Laboratory (BFRL) program on service life prediction for materials used in construction (such as paints, coatings, and roofing materials) focuses on techniques for measuring durability. Recent accomplishments include the construction of a 2-m ultraviolet integrating sphere that can be used to examine the durability of materials exposed to combinations of well-controlled environmental conditions. This is a significant improvement over techniques commonly used in industry today, which can vary widely from measurement to measurement.

Researchers in the Physics Laboratory (PL) are world leaders in the fabrication and analysis of thin magnetic layers and other nanoscale features. This group is now attempting to develop the measurement capability to allow scientists to probe the underlying physics in quantum confined structures on a nanometer scale. To this end, it has recently completed the design and assembly of a unique facility for fabrication and measurement of such structures. Such measurements are valuable as researchers across the nation seek to understand and develop devices and applications based on nanotechnology.

Materials Science and Engineering Laboratory (MSEL) staff are using the laboratory's outstanding measurement capabilities to better understand copper metallization techniques for chip interconnection. Electrodeposited copper is quickly gaining acceptance as a replacement for aluminum in chip interconnection technology. The quality of the copper fill in these processes is dependent on the use of added agents to promote complete fill and the desired final materials properties, but the mechanism of action of these agents is poorly understood. Recent measurements in the MSEL have begun to illuminate these mechanisms so that industrial processes can be more efficiently designed and optimized.

The Chemical Science and Technology Laboratory (CSTL) continues its development of cavity ring-down spectroscopy (CRDS) for use in sensing low-level gaseous contaminants in manufacturing processes. The measurement precision that the laboratory has obtained with this method is already very close to the 2001 target for measuring water vapor in semiconductor fabrication lines given in the International Technology Roadmap for Semiconductors.1 The laboratory has also miniaturized this technology to create a CRDS optical cavity that can detect and quantify small amounts of materials in contact with or adsorbed on a surface. CSTL researchers are now exploring its potential as a miniature detector for lab-on-a-chip use.

The Information Technology Laboratory (ITL) and the MSEL have jointly developed a general software tool for modeling real material microstructures —the object-oriented finite-element (OOF) analysis system. The result of an effort initiated in support of an MSEL research project, the OOF system is now used by a number of major companies. Further refinement of the software has attracted


Semiconductor Industry Association, International Technology Roadmap for Semiconductors, Semiconductor Industry Association, San Jose, Calif., 1999.

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