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It’s a new year, and with it begins a new phase and renewed excitement about the University of Notre Dame’s cutting-edge research in the realm of nanoelectronics.
MIND, which stands for the Midwest Institute for Nanoelectronics Discovery, enjoyed a highly productive initial phase in its first three years. It is now poised to transition into a second phase.
|Robert Dunn, Managing Director, Notre Dame Center for Nano Science and Technology and MIND (Midwest Institute for Nanoelectronics Discovery) talks with Indiana Governor Mitch Daniels after a meeting of the Indiana Economic Development Commission at Stinson-Remick Hall. Photo by Matt Cashore/University of Notre Dame|
The next stage of MIND, dubbed MIND 1.5, recently received approval for a contract extension for another two years at $1.1 million per year beginning January 1, 2011. MIND 1.5 will focus on continuing development of the most successful devices and applications borne from the basic research discoveries so far uncovered.
MIND was established by the Semiconductor Research Corp.’s Nanoelectronics Research Initiative, a national consortium that funds four separate centers around the country. The original MIND team, based at Notre Dame, included more than 70 researchers at eight universities, including University of Michigan, University of Illinois, Purdue University, University of Texas at Dallas, Penn State University, Cornell University and Georgia Tech University. The MIND 1.5 team is now comprised of researchers from Notre Dame, Purdue, University of Texas and Penn State. Its sponsors are IBM, Intel, Global Foundries, Micron, Texas Instruments and the National Institute of Standards and Technology.
When MIND researchers initially set off on their journey of inquiry and discovery, Jeffrey Welser, director of the Nanoelectronics Research Initiative, described the MIND 1.0 phase as a time to “let a thousand flowers bloom.”
The idea was to plant and nourish the seeds of various promising nanoelectronics projects to see what would “take root,” so to speak. Now that the first flowers have bloomed, MIND’s leadership team has determined what direction to take next.
MIND also will continue to have a leadership role in evaluating and benchmarking all new device technologies that are being developed across the Nanoelectronics Research Initiative. Notre Dame will continue to host leading NRI researchers at a summer workshop, which serves as a forum to compare and evaluate the various technologies pursued in all four Nanoelectronics Research Initiative centers.
The race to replace the transistor
Robert M. Dunn, managing director of MIND, says the Nanoelectronics Research Initiative has asked each of its centers, including MIND, to focus on the two most-promising research approaches that have the greatest probability of successfully replacing the current transistor technology, known as complementary “metal oxide semiconductor field-effect transistors” or MOSFETs. The industry has relied on these devices for the past 25 years.
The MIND 1.5 grant involves Penn State, Purdue and UT Dallas as partner universities with Notre Dame.
|Clean Room in Stinson-Remick. Photo by Matt Cashore/University of Notre Dame|
“Other areas of focus for this next phase include expanded research in circuits and architecture design, device demonstration, as well as continued participation in the emerging device benchmarking project,” Dunn says. “What this means is that we are comparing the performance of new and emerging technologies with other devices being developed at the other NRI centers.”
With each of the four Nanoelectronics Research Initiative centers now focusing their efforts on their top technologies for replacing the conventional transistor, MIND is turning to its two lead technologies with the most potential: tunnel field-effect transistors (TFETs) and nanomagnet logic devices.
TFETs are low-voltage semiconductor switches used for computing and low-power portable applications, used in devices like cameras, cell phones and MP3 players. Nanomagnet logic devices are permanent magnets (created on a nanometer scale). They also hold great potential for computing, because they are low power and are nonvolatile, which means they can retain stored information even when the power is switched off.
During MIND’s initial phase, such TFETs were successfully created in compound semiconductors (rather than in traditional silicon-based materials) for the first time. These new TFETs are advantageous because they can outperform even the very best types of conventional transistor technology in use today. Why? Because they effectively deal with the issue of quantum tunneling — when electrons break the rules of classical physics by passing through thin barriers. This tunneling phenomenon has led to the leakage of current in today’s transistors, undermining their energy efficiency, thereby creating a major technological roadblock in their continuing development in the years to come.
In contrast, the experimental new TFETs created at MIND actually harness the current. As a result, the current doesn’t leak, and it is controlled in a way that makes the transistor even more energy efficient.
These experimental demonstrations have led to two U.S. patent filings and two provisional patent filings.
“We are encouraged by the experimental findings,” says Professor Alan Seabaugh, director of MIND. “We now see the key technical challenges and know where to focus the research effort.”
Specifically, the promise of TFETs hinges on achieving higher currents and lower-operating voltages. However, in order to improve this technology, MIND researchers are working on another vexing issue: the presence of unwanted charges that hamper the efficiency of current flow in the TFET device. In short, researchers are trying to determine the sources of these undesirable charges, and to figure out how to turn them off.
The other technology MIND 1.5 is forging ahead with is nanomagnets. MIND researchers have conducted experiments to explore whether nanomagnet technology is a promising alternative to perform what is known as “digital logic.” The results have clearly demonstrated that this is the case.
“The simplest and most common digital logic system is based on the answers to ‘yes’ or ‘no’ questions,” Seabaugh says. “In electronics we represent the ‘yes’ and ‘no’ by high- and low-voltage levels, or in new ways, such as the orientation of a nanometer-scale magnet.”
In essence, digital logic systems are the very heart of all computing devices, from laptops to mainframe computers.
“Since magnetism is already used for data storage as in disk drives, our work on nanomagnet logic opens the way to all-magnetic information processing systems, combining memory and logic,” explains Wolfgang Porod, professor of electrical engineering and director of the Center for Nano Science and Technology. “This work would enable instant-on computers, as well as have important applications for mobile systems due to low power.”
|Photo by Matt Cashore/University of Notre Dame|
The results from these experiments were a key factor in the awarding of the MIND contract extension by the Nanoelectronics Research Initiative, says Seabaugh.
Advances in TFET technology and nanomagnets at Notre Dame constitute one of the major milestones for MIND in the past several years. Several other highlights of the MIND initiative are worth applauding as well.
For example, the design, growth and fabrication capabilities were pushed to the atomic scale for low-power transistors. Notre Dame researchers demonstrated a technique for growth of one-atom-thick carbon channels for transistors — a material called graphene.
“This material is one of the most promising materials for low-power tunnel transistors,” says Seabaugh. “In fact, the Nobel Prize in Physics was awarded this year to the discoverers of graphene.”
Graphene is especially promising because, as a sheet form of carbon, only one atom thick, it is stronger and lighter than copper, yet can carry more current. It can be used for wiring or configured to be a transistor, switching at higher speeds than other semiconductors.
Another major milestone for MIND researchers in only the past year was the improvement of their capability for forming one-layer sheets of graphene into ribbons, a process that is essential for its use in transistors.
“At the start of the year, the best we could do was around 20 nanometers in width,” Seabaugh says. “Yet by using a clever processing trick, we have been able to reduce the ribbon width down to 12 nanometers, and we now are working on the next factor of 2.5. Our goal is to reach 3-5 nanometers of width in our tunnel transistor structures.”
Another significant grant awarded to MIND
Aside from the applied research focus that characterizes MIND 1.5, other noteworthy events mark the start of the new year.
The U.S. Defense Advanced Research Projects Agency (DARPA) recently announced that Notre Dame is the main contractor for a $9.9 million grant on nanomagnet logic research. Other research partners involved with this grant are the University of California Berkeley, the Technical University of Munich and private-sector firms IBM and Grandis. The funding became active last fall and is expected to last for four to five years.
Michael Niemier, assistant professor of computer science and engineering, says the DARPA grant relates to MIND 1.5, because one of the outcomes that the sponsors for this would like to see is an integrated circuit involving a new technology for transistors by the end of two years.
“The research efforts associated with the DARPA grant can leverage work associated with MIND 1.5; the work that we do will be beneficial to MIND and vice versa,” Niemier says. “MIND is investigating what a nanomagnet logic system would ultimately look like and how it works as a replacement for conventional technologies.”
He explains how, in conventional electronics, most computation is charge-based, and such computation generates a lot of heat. Think about how hot a laptop can get after it’s been on for a while. Nanomagnet logic devices, however, should produce much less heat and can retain information without needing power.
Niemier and his colleagues have been working on the magnetic logic project for the past five years, and the success of the emerging technology led them to write a proposal to expand the experimental effort, which can now begin.
“We have a really good team with a diverse set of skills,” he says. “The four core principal investigators (from Notre Dame) working on the project form an excellent feedback loop. We wouldn’t have advanced as far as we have if it weren’t for this group and our team effort. Moreover, adding additional partners from other universities and industry only enhances the research effort.”
The new Stinson-Remick Hall open for business
Dedicated this past September, the Stinson-Remick Hall of Engineering is home to MIND, as well as Notre Dame’s Center for Nano Science and Technology. The importance placed on the future of nanotechnology research at Notre Dame is evident by the University’s decision to devote 45 percent of the building’s resources to nanotechnology.
Encompassing 160,000 square feet, the $70 million Stinson-Remick building includes such cutting-edge features as a 9,000-square-foot clean room with air filtration 20,000 times purer than natural air for processing and fabricating nanoscale semiconductor devices. Additionally, Stinson-Remick was designed to minimize building vibration — a critical feature for the delicate manipulations involved in nanotechnology.
The opening of the state-of-the-art clean room facility within Stinson-Remick was notable for a number of reasons.
Last year Seabaugh and colleagues at Notre Dame worked with top instrument-manufacturing companies to specify cutting-edge fabrication tools to bring world-class fabrication capability to South Bend.
“In the first quarter of this year, we plan to take delivery of eight new processing tools for the clean room for a variety of specialized uses,” Seabaugh says. “With these tools, we will develop nanoelectronic devices that are smaller, faster and more energy efficient.”
The new tools are close to arriving, but already Seabaugh is clearly anticipating the benefits for MIND as it transitions into its new phase in this new year.
“MIND has been highly productive, as measured by the number of technical publications, conference presentations and patent disclosures,” he says. “And, despite being more than two years into this initiative, MIND research is still ramping up, with 2011 promising even more.”
Dunn agrees and is appreciative of the support that has propelled MIND to achieve all it has thus far.
“MIND is delighted to have the Nanoelectronics Research Initiative’s continued support for the next two years, as well as the ongoing support of the City of South Bend and the State of Indiana,” he says. “We are particularly excited to have the opportunity to extend the research in our two lead technologies of tunneling transistors and nanomagnet logic.”
Look for more groundbreaking discoveries and the possibility of additional research and application phases as MIND continues to move forward.