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        Summer 1999 Newsletter

The Big Picture on Nanoscale Engineering

The SNF & NNUN

Joanna Evans

"The way I like to describe NNUN facilities is basically as sandboxes for people to play in. We don't control the research people work on, we simply provide the means for them to do their science. So although we can't guarantee major break-through research results in area X or Y, what is entirely predictable is that there are going to be some pretty remarkable things coming out of this program."
--Professor Jim Plummer, SNF Director

 

At the Stanford Nanofabrication Facility (SNF), the ability to manufacture structures smaller than a human blood cell is driving forward research in biology, medical devices, chemistry, optoelectronics, physics, agriculture, MEMS, and materials, as well as in the traditional fields of microelectronics and semiconductors one tends to associate with microfab facilities.

Originally known as the CIS lab when it was built in 1985, the SNF lab changed titles in 1994 when it became part of the National Nanofabrication Users Network (NNUN), a program funded by the National Science Foundation (NSF) in recognition of the need for research labs devoted to fostering education and diversity in the area of nanofabrication. The NNUN program supports five university facilities that offer a complementary array of equipment and technology to academic researchers and industry users. Each of the universities (Stanford, Cornell, Howard, UC Santa Barbara and Penn State) has a specialized focus, though they all support work in a range of technical areas.

One of the new sectors the NNUN has chosen to focus on recently is the area of biology and biomedical devices. Micro-scale bio- and biomedical engineering has experienced rapid growth in recent years, and the NNUN has sought to address this increased interest by promoting partnership among scientists and disciplines. The SNF hired Biotechnology Liaison Mary Tang last year to promote this specific area of research by building bridges between the physical and life science communities. The SNF hopes to facilitate cross-disciplinary collaborations between researchers with similar interests and complementary expertise through seminars, workshops and other resources. (More information is available at the NNUN Biotechnology Website: http://www.nnun.org/biosite/biosite.html.)

SNF users at a wafer cleaning station.

 

Thanks to NNUN support, SNF users have already achieved some exciting results. One of the most interesting success stories to come out of this field recently is the artificial retina, developed and built at the SNF by two brothers, Drs. Vincent and Alan Chow, one an ophthalmologist, the other an engineer. In some diseases of the eye, the signal processing cells underlying the retina are still functional, although the photoreceptors in the retina itself are not. To mimic the photoreceptor network, the brothers built a dense array of microphotodiodes on a silicon microchip only three millimeters in diameter. When implanted in place of the damaged retina, the microphotodiodes transduce light into electrical impulses, thus allowing "visual" sensing by the signal processing cells. Although still undergoing refinement, this "bionic" eye could eventually restore eyesight to millions of people who suffer from diseases like retinitis pigmentosa and macular degeneration.

The Chows' retina project exemplifies the interdisciplinary approach the NNUN seeks to nurture in American industry and academia. Through seminars, workshops and use of the Web for increased visibility, the SNF and NNUN continue to recruit researchers from a variety of backgrounds and differentiated perspectives, in an effort to build the most vibrant and heterogeneous research environment. "The NNUN is really pushing for a multi-disciplinary approach to problem solving," says Tang. " And we're looking to the nontraditional areas of research to do that."

 

"I think broadly sharing the facilities across many disciplines is by far the best solution."

-Jim Plummer

Each of the five university sites has a representative serving on the Network Access Committee (NAC), a group that reviews proposed projects and ensures the smooth flow of work from concept to completion. Researchers, whether from Stanford or outside organizations, propose projects to the NAC via phone, fax, email and the Web. Once a project is accepted, the NAC decides which site is most appropriate for the research and assigns a liaison to assist with technical questions, equipment use and general acclimation. Stanford's representative to the NAC, John Shott (Senior Engineering Research Associate) oversees this process for the SNF.

SNF users working with a Poly Silicon Etcher from LAM Research

 

One of the biggest challenges facing Shott and his colleagues is avoiding the cross-contamination issues that may arise in a lab with so many different users and materials. The SNF accommodates projects that employ a broad variety of metals and insulators, requiring the SNF staff to be vigilant in monitoring the materials and ensuring that they don't contaminate other projects. "Striking that happy balance is, on a day-to-day basis, the single trickiest aspect of running a facility like the SNF," says Shott.

Researchers can also work off-site, accessing NNUN resources (such as process libraries, device simulators and fabrication testing) with the assistance of their technical liaison. Currently, only a small percentage of projects (roughly 5%) are handled in this way, but Shott hopes that number will grow over time, along with the lab's capability of accommodating complex projects remotely. "I think it's a great way of giving a broader population access to the capabilities in our lab," explains Shott.

The smorgasbord of equipment available at NNUN facilities is certainly a strong draw for prospective researchers. Although much of the equipment is available commercially, start-up companies and researchers with highly innovative projects often have difficulty competing for lab time in the marketplace. "At a company, you have to specify what you want up-front," explains Tang. "You don't have the freedom to explore a variety of equipment and resources as you can at an NNUN lab."

World-class research is the primary objective of the SNF and the NNUN, but there is another, more pragmatic, benefit of a diversified user base. Fifteen years ago, the CIS lab had a narrow focus on mainstream chip research. But that strategy required a critical mass of users to offset the high operating costs, and before the advent of the NNUN, the lab averaged only 60-70 users a month. Today, with a broader spectrum of scientists and research within its walls, "business is booming." In any given month, there are 140-150 researchers in the lab, working on a variety of different projects, for a total of over 350 different researchers each year. The lab user base tends to be roughly 60% Stanford students and faculty, 25% industry and 15% outside academics. "I think broadly sharing the facilities across many disciplines is by far the best solution for this facility," maintains Professor Jim Plummer, Director of the SNF (and new Dean of the School of Engineering), "The NNUN program really saved us." One of the challenges facing the NNUN, and the SNF in particular, is the issue of "experiment saturation." The SNF lab currently has room to accommodate almost all of the proposed projects it receives. But the lab can only support a limited number of users at any given time. A few years down the line, it may have to start exercising greater selectivity. "Frankly, I hope we never get to that point," says Plummer, who notes that bringing other facilities into the network and expanding the number of research sites may be a solution. "That's a better response than beginning to turn away proposals," he concludes.

The National Science Foundation doesn't fund programs for more than ten years without re-competing them, so SNF's most recent renewal for another 5-year cycle was its last without having to vie with other university facilities. Assuming that the NSF continues funding the NNUN program, the field of competition will be wide open five years from now. "I think if we had to go through that competitive process today, Stanford and its NNUN partners would win hands down," says Plummer, "But if we don't continue to emphasize a diverse user base and new application areas over the next five years, that may not be the case. You can't assume just because you have something now, that you'll have it forever."

An exciting component of the NNUN is the Research Education for Undergraduates (REU) program. This nationwide program, in its third year of operation, brings roughly 40-45 undergraduates to the five NNUN sites each summer. As the West and East Coast hubs with the largest university facilities, Stanford and Cornell get the lion's share of these students. Candidates from all over the country apply for the REU program. Those who are accepted get trained to work in the lab and then undertake graduate-level research for the following ten weeks.

REU students are recruited from smaller schools, and people who wouldn't necessarily have access to major research facilities, especially women and minorities, are particularly encouraged to apply. The program also considers students who may not necessarily be thinking about going into engineering. "What we try to do is show them what graduate level research is all about," explains Mike Deal, who co-directs the Stanford REU program with Jane Edwards. Students join a research group from the wide selection of areas at the SNF. At the end of the ten-week program, they hold a "convocation," a sort of mini-technical conference where they present their research to staff members and other students. The convocation includes a feedback session in which Deal and Edwards get comments on the success of the program. "About 95% of the feedback is favorable," says Deal, "They really appreciate having this opportunity, and we really enjoy having them, too."

Deal hopes that students will carry favorable reviews of their experience at Stanford back to their home institutions and "spread the word" about the fertile ground at the SNF and how researchers can make use of it. "It's getting harder and harder to fund research facilities like this one and yet programs like the NNUN are critical to the science and engineering communities at large," says Deal.

CIS partner companies make contributions to REU student research through CIS Seed Research funding. What's in it for CIS? To begin with, the exposure of young students to exciting cutting-edge research can serve as a wide recruiting net, enlisting new minds into engineering fields. REU students are undergraduates in the process of selecting academic areas for graduate study. "By exposing these students to semiconductor technologies, CIS partner companies are in a sense widening the pool of people who go into science and engineering. Some students will of course choose to follow that avenue of study who otherwise would not have," says Plummer, "And of those individuals, some will undoubtedly end up working for CIS member companies."

CIS Seed Research funds also support the NNUN User Grant Program, providing underfunded researchers with the means to do their work. This program catches ideas in their infancy, seeding them before proposals have gone out and big contracts have been signed. Although the user grants are small, the fast turnaround protocol is definitely an attractive feature that contrasts sharply with traditional funding structures, in which it can sometimes take more than a year from proposal to receipt of funds. In the User Grant Program, the turnaround time is closer to one month. Many of the ideas that have been nurtured in this program have grown into major government-funded projects.

The NNUN program has provided significant advantages to CIS and the SNF. The willingness of CIS partner companies to see the lab take on this broader mission has been pivotal to its success. Thanks to the NNUN, the burden of lab infrastructure costs has been lifted so that CIS research funds can be directed exclusively at research. "Member companies understood the rationale for doing this and they were very supportive," says Plummer, "In the end, I think it was the only viable option."