Commerce's NIST Celebrates 40 Years of Semiconductor Research in Partnership with Industry

The Commerce Department and the U.S. semiconductor industry next month will celebrate the 40th anniversary of a partnership in a field that has enabled such technological advances as the development of sophisticated diagnostic medical devices, laptop computers and home breadmaking machines. These advances have profited from the support the industry has received in the past 40 years through the semiconductor research program at the Commerce Department's National Institute of Standards and Technology.

From a couple of projects on transistor measurements in the Tube Laboratory to today's multidisciplinary National Semiconductor Metrology Program, some aspects of NIST's semiconductor work have remained consistent and dependable:

• selection of research efforts that are guided by the semiconductor industry;
• commitment to fulfilling the measurement needs critical to semiconductor research; and
• proven effectiveness in transferring research results to those who can benefit from them.

Striving to achieve the next milestone is something NIST does routinely. "I think it is not enough to be the keeper of the national electrical standards, not enough to be assigned the lead role in measurements by Congress, and not enough to be asked by industry for help and directed by Congress to provide it," said Judson C. French, director of NIST's Electronics and Electrical Engineering Laboratory. "There has to be a mechanism for addressing these roles that actually works." History has shown that NIST has one.

A Tradition of Excellence

It all began in July 1955, when electronics scientist Judson French was entrusted by management at the National Bureau of Standards, NIST's predecessor organization, with a budget of $10,000 and a mission: to see what kind of support NBS could give to the growing transistor industry. French approached the American Society for Testing and Materials and the Electronic Industries Association to help define a need that NBS could fulfill. Each organization identified measurements critical to dealing with the great discrepancies in both manufacturing and product specifications and that were still unresolved by member companies. So, armed with a project from each organization, NBS embarked on a new program of measurement research that would, decades later, inspire the Semiconductor Industry Association to note that "NIST is the only place in the U.S. where the broad range of measurements needed for semiconductor processing are routinely and systematically developed."

One problem identified early on was the measurement of silicon resistivity, the most important property of semiconductors for device design and manufacturing. Discrepancies in measurements within and between companies were many times the allowable uncertainty. Initially, industry believed that only a destructive method could provide the precision required. However, the NBS scientists showed that it was possible to make a practical, non-destructive method greater than 10 times more precise than conventional procedures. The new method proved useful for both standards laboratories and manufacturing processes. It provided the basis for five industrial standards set by the private sector and led NBS to produce several resistivity standard reference materials, which industry continues to purchase to this day to calibrate their measurement instruments.

Conducting research that filled a key industry need soon paid off in economic terms. A benefit-cost study conducted after the first major phase of the resistivity work showed that economic benefits, in marketplace transactions alone, were estimated by industry at over $30 million—a return of greater than 100 times the cost of the NBS work.

At some points along the way, NBS found ways of partnering with other federal agencies to continue developing measurements for integrated circuits for manufacturing and the marketplace that would benefit its industrial customers. For example, in the early 1970s, NBS was requested by the Defense Advanced Research Projects Agency to help the Defense Department develop integrated circuits with increased performance and reliability levels.

Both military and private-sector organizations profited from the measurement improvements. In one case, the investigation of wire bonding of integrated circuits established new procedures—now implemented in commercially available equipment—that increased circuit yields by as much as 35-fold and made possible large military hybrid circuits that utilize more than 500 wire bonds each.

In 1981, Charles River Associates conducted studies to investigate the economic benefits provided by NBS' work in semiconductor technology. These studies found that industry respondents received several benefits from the use of NBS results:

• improved product reliability,
• increased production yields,
• increased ability to meet customer specifications,
• improved product features,
• cost reductions, and
• new directions of company research.

The report concludes that "the overall industry productivity level was approximately one percent higher for the years 1973 to 1977 [which were covered by the studies] than it would have been had the technical information acquired from NBS not been available" and that the median rate of return to the economy and society on investment in the NBS work was 140 percent per year. Later comparisons with industry data showed that NBS had provided four percent of the total industry productivity increase during the period.

NIST's unique role in providing measurement research and services for the semiconductor industry has harvested a number of successful interactions. For example:

• NIST's work on photomask linewidths led to a tenfold reduction of intercompany measurement discrepancies, stimulated the production of new instrumentation, extended the range of use of optical microscopes, and provided techniques and calibration standards that have been adopted industry-wide. Hewlett-Packard, IBM and Texas Instruments, for example, reported that they stopped using their internal standards and adopted those of NIST. A study of the benefits of this work estimated a $30 million annual savings to the photomask producers alone.
• NIST created the world's most accurate ellipsometer to develop and issue standard reference materials for measurement of silicon dioxide layer thicknesses between 10 and 200 nanometers, measurements critical to industry for precise manufacturing control.
• NIST stimulated the first marketplace use of integrated circuit test structures, which are devices formed on the wafer during manufacture that can be probed electrically to measure properties of materials, quality of processing steps, device operation and mechanical properties.
• Results of NIST's methods of evaluating susceptibility to electromigration—which causes the interconnect metal on modern integrated circuits to fail—have been used by at least 14 companies. An independent study reported that benefits to this industry, including reduced production and transaction costs as well as improved research efficiencies, led to an estimated aggregate social rate of return of 117 percent.

Someone not accustomed to metrology issues may wonder why an industry with a job as technology intensive as manufacturing semiconductors would need any help measuring materials, processes and devices. In fact, high-tech industries "push the envelope" of measurement technology—it is precisely these industries that need the measurement infrastructure NIST provides.

Development of advanced measurement technology for use by large numbers of organizations in the public domain is a high-cost, high- risk undertaking where diffuse benefits discourage action by an individual company or mission-oriented agency, and anti-trust regulations inhibit company cooperation. NIST is in a unique position to respond to these needs because of its primary mission in measurements and support for industry. The agency's neutrality, which arises from its freedom from buyer, seller or regulatory roles, allows it to gather the information necessary to synthesize non- proprietary methods that are universally applicable and then test the methods in inter-lab experiments.

Strong Partnerships Today

Sometimes, casual interactions between researchers lead to real-life success stories, as in the case of Analogy, Inc., of Beaverton, Ore., makers of simulation software tools for designers of electronic circuitry. Daniel Diebolt of Analogy attended a technical conference for electrical engineers where he heard NIST's Allen Hefner give a talk on an important, relatively new component of power electronics called an insulated gate bipolar transistor (IGBT). The cooperative research that resulted from their meeting led to new simulation tools that already are changing the way Motorola makes some of its electrical products and the way Ford Motor Co. makes cars. "We view this as a strategic collaboration, and we want to continue down this path," said Peter Decher, Analogy's director of modeling.

The NIST researchers themselves provide an uncommon resource to their industrial partners, who enjoy ready access to professionals whose careers have focused on semiconductor measurements. "Almost everyone here working on semiconductor research has frequent interaction with industry—many on a daily basis," said Robert Scace, manager of the National Semiconductor Metrology Program at NIST, which began in 1994 at the request of the semiconductor industry.

Industry representatives agree. "U.S. manufacturers have the advantage of NIST, the preeminent laboratory in the world in most aspects of the metrological know-how needed for semiconductor manufacturing," the Semiconductor Industry Association stated recently when recommending to the Semiconductor Technology Council that funding for NIST's National Semiconductor Metrology Program should be increased to address critical technology gaps.

The experience that comes with a long tradition of measurement research coupled with the intimate connection with one of the world's fastest-paced industries have taught those in the NIST semiconductor program to keep their eyes on the road ahead. Theirs is a unique ability to work toward long-term results for an industry with 36- month product cycles.

Terry Francis, director of global microcontamination at Applied Materials, recently summed up his organization's interactions with NIST measurements research by saying, "We strongly support and encourage NIST's efforts to produce standards and cooperate with the American Electronics Industry to solve key problems."