QMT Features: September 2008
Focus on NIST
The US National Institute of Standards  and Technology (NIST) plays a significant role in underpinning  US economic and technological development. By Thomas Shattuck


The National Institute of Standard and Technology, NIST, is a non-regulatory agency under the United States Department of Commerce that aims to improve the standards of measurement to provide economic  stability and technological development. 

NIST received approximately 755.9 million dollars this past year to fund its various projects and is currently seeking a 7.4 percent increase for the year 2009, though only a 1.4 percent increase has been approved by the US Congress.  With the budget significant returns have been made.  For every dollar spent on metrology, the Institute calculates a return of three dollars and thirty cents throughout  industry as a whole.

Within NIST, the Dimensional Metrology Program (DMP) aims to improve American competitiveness by providing metrological standards and tools for industries with a significant U.S. presence.  DMP achieves their goals in many ways, most notably through coordinate-measuring machines (CMM) - particularly transportable systems such as laser interferometers and laser trackers.

The large scale metrology industry is rapidly moving to optical measurement systems. Unlike large fixed placement CMMs, these new systems can be easily transported to different measurement sites, have significantly lower capital equipment costs, and allow factory floor space to be rapidly reconfigured.

New optical technologies that provide absolute distance measurement (ADM) capability eliminate the need to transport retroreflectors from the system to the workpiece and the associated problems of beam breakage. For that reason, measurement technology using ADMs has exploded in recent years and numerous firms are developing new products and measurement services. The United States claims to lead the world in this technology, particularly in the development of ADM laser trackers.

The DMP is supporting this crucial technology through development of a high accuracy 60 meter test range that can calibrate ADM ranging systems. Direct assessment of the errors in these (often highly proprietary) ADM systems helps manufacturers of this technology to improve the accuracy of their equipment and gives users confidence in the measurements. Using NIST’s existing tape calibration facility, augmented with a newly developed high accuracy long range interferometer system, represents a unique US national resource. Current test range calibration uncertainties are U(k = 2) = 2 µm + 3 × 10-7 L for cooperative targets (specially made to be ADM friendly) and U(k = 2) = 10 µm + 1 × 10-6 L for noncooperative targets .

Along with improving metrological tools, the DMP is also interested in entrenching US technical standards in new fields.  They have succeeded in several key areas including measurement uncertainty, traceability and standards for Cartesian CMMs.  Furthermore, the DMP hopes to develop standards for laser scanning sensors  increasingly used with various types of CMMs.  This will allow for the accurate measurement of objects in the <50 nanometre range. 
Examples of improvements in ultra precsion measurement include the creation of what is referred to as the "M Cubed", or the molecular measuring machine.  It is currently located underground in a clean room at NIST's metrology wing to prevent environmental disturbances.  Its primary use is ultra precise two-dimensional measurements and is able to draw lines on silicon as small as 10 nanometres wide and 4 nanometres high. 

In the Precision Engineering Division (PED), under the supervision of Doctor Michael Postek, several advances in metrological tools have been made.  PED is split into multiple groups focusing on different aspects,  all serving NIST's mission objectives. 
Like other divisions, the PED serves as both a research organization and as a calibration service.  The division has made great strides on the smaller scales including the creation of a 150 x 150 millimetre reference artifact with less than 30 nanometre measurement uncertainty and has completed experiments for next generation of single crystal critical dimension reference material. This allows for the accurate comparison of size and provides a point of reference for measurements on a nanoscale. 

Other recent PED accomplishments include blind tip estimation for critical dimension atomic force microscopes.  Blind estimation is particularly useful because the detailed shape of the tip characterizer need not be known. Until very recently, blind reconstruction could only be applied to conventional non-reentrant tips. The surface of such a conventional tip can be represented by a single-valued function. Blind reconstruction has now been extended to objects with multi-valued heights by using a dexel-representation for such objects.

As for the future of metrology and the growth of manufacturing in the U.S. and internationally, Dr. Postek believes that NIST will play a central role.   " NIST’s specific role as a neutral third party with technical excellence provides NIST a unique role for national and international standards. Well written standards have positive externalities to industry.  These externalities include the avoidance of costs for individual (i.e. idiosyncratic) testing, optimizing capital purchases (by allowing meaningful comparisons between different products) and the lowering of  barriers to new technology adoption through  increased confidence and technical information.”  Dr Postek says that early adoption allows economies of scale to take place, letting mass production create affordable, reliable tools sooner.  Also, with the ability to compare similar products, optimal decisions can be made, promoting intelligent investments of capital and sustained growth.

www.nist.gov
E-mail: thomas.w.shattuck@Vanderbilt.Edu

 

  
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