National Semiconductor Metrology Program travels Roadmap to future needs
12/01/1996
National Semiconductor Metrology Program travels Roadmap to future needs
Lorraine Savage, Associate Editor
The fast-paced development of integrated circuits requires dramatically improved measurement tools and tighter controls of more numerous and more sophisticated manufacturing processes to keep advanced microelectronic manufacturing competitive. Acknowledging this but noting the industry`s limitations, Robert Scace, director of the Office of Microelectronics Programs (OMP), which operates the National Semiconductor Metrology Program (NSMP), said, "Right now, some requirements of the National Technology Roadmap for Semiconductors cannot be met. For example, the Roadmap says that we ought to be able to measure critical dimensions to within a few nanometers, and 50 is the best we can deliver."
This is one obstacle that the NSMP has been created to overcome. The NSMP, with a current annual budget of $11 million supporting 23 internal projects, serves metrology and measurement needs that are not being met elsewhere, and aims to enhance future American competitiveness.
Established in 1994 by the National Institute of Standards and Technology (NIST), the NSMP draws on a full range of NIST expertise in semiconductor metrology, focusing on mainstream silicon CMOS technology addressed by the Roadmap.
The Semiconductor Industry Association (SIA) asked the Department of Commerce to fund the NSMP in support of the Roadmap. NIST`s Electronics and Electrical Engineering Laboratory (EEEL) is working with the SIA to identify and respond to key measurement technology needs that must be met in the next 15 years for the industry to manufacture future generations of chips. The EEEL`s OMP manages NIST`s relationship with the SIA, SEMATECH, and the Semiconductor Research Corp. (SRC). The OMP is responsible for maintaining the relevance of the NSMP`s specific projects through direct industry contacts and regular interaction with industry consortia.
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The NSMP addresses the Roadmap`s challenges by conducting, often with industrial collaborators, projects associated with lithography, interconnectivity, materials and bulk processes, and packaging (Table1). The program funds and manages these in-house metrology development activities. Six NIST laboratories conduct NSMP-sponsored work: Electronics and Electrical Engineering, Manufacturing Engineering, Chemical Science and Technology, Physics, Materials Science and Engineering, and Building and Fire Research.
NSMP work includes measurement development programs in a number of areas, listed in Table 2.
As part of these internal projects, the NSMP with NIST operates in industry partnerships. NSMP works with 23 integrated circuit makers, 46 manufacturing equipment and materials suppliers, 37 universities, 12 government agencies, seven standards organizations, and three industry consortia. These relationships allow NIST to learn from its collaborators and vice versa. Collaborations may range from a brief professional dialogue between two people working in related technical areas to multiyear associations involving extended residence of the collaborator at NIST. Partnerships that operate under NSMP include Cooperative Research and Development Agreements (CRADAs), contracts, facility use agreements, guest researchers, industry fellows, inter-institutional agreements, licenses of NIST intellectual property, memoranda of understanding, and simple "handshake" collaborations.
The industry participates in NSMP programs by contributing materials, special processing, and sometimes pieces of equipment needed for the semiconductor programs. Firms also provide private views of metrological needs that are factored appropriately into the NSMP`s plans.
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Researchers working in electronics and electrical engineering, manufacturing engineering, chemical science and technology, materials science and engineering, and fundamental physical sciences may staff NSMP projects.
"Being involved in the Roadmap process is a good way to learn about the issues from the people who have the problems," noted Scace. "We always go and talk to the industry. We have people involved in the various places where semiconductor-related standards are done, such as the American Society for Testing and Materials, as well as technical meetings like the IEEE and SPIE, where there are discussions about measurement. We`re also involved with the SRC and SEMATECH."
In recent months, the NSMP has completed or initiated several metrology projects needed by the semiconductor industry.
A NSMP project for near-term completion involves a new kind of thermocouple for measurement of temperature in such places as a diffusion furnace. Scace explains that existing platinum and platinum iridium are not accurate enough or stable enough at needed temperatures. The NSMP has been studying metallurgical effects when the alloy is held at a high temperature for a long time.
A project to be completed in about a year will improve the ability to measure moisture in gases from about 10 ppm down to about 10 ppb, or a factor of about 1000 improvement. The first tool is being tested and is expected to be on stream by the end of this month. The second tool should be up and running by mid 1997. Ongoing projects include new calibration services for ultraviolet light meters used to measure light intensity in steppers; and fundamental measurements on the physics and chemistry of ionized species that occur in plasma processing, plasma etching, and plasma deposition. The latter long-term research project will provide numbers to be used to model how plasma processes work.
An accomplishment of note, says Scace, is the superconductivity work being done in NIST`s Boulder, CO, lab. Now, an energy dispersive x-ray detector attached to a scanning electron microscope examines x-rays that come off the material when the electron beam strikes it, and identifies elements from the spectrum. "The problem is that this detector only has an energy resolution of about 100 electron volts," explains Scace. In some cases, peaks from more than one element will overlap at the same place, such as with titanium and nitrogen. "We have a new device based on microcalorimetry which actually measures the heat from one x-ray quantum that lands on a superconducting piece of material. The energy resolution is a factor of 10 better than you can do with other instruments. And that`s just the lab prototype. This will revolutionize this kind of analysis."
Results of NSMP research are disseminated back into the semiconductor industry. "We write reports and give talks at meetings," said Scace. "We also advertise. We have a catalog of reference materials and calibrations that we do on a regular basis. We put a lot of effort disseminating information back into the industry."
Government funding for NSMP doubled in FY95 to $10 million. Although the SIA supported a budget of $19 million for FY96, no funds were appropriated for this fiscal year. The program, when fully funded, will have $25 million.