Nanotechnology, the ability to manipulate and organize matter and structures from the atomic up to the molecular scales, is widely viewed as the most significant technological frontier being explored. Generally meant to define devices with feature sizes of 100 nm or smaller (1 nm equals the span of about seven to 10 hydrogen atoms), nanotechnology is being heralded as a vastly more powerful technology than ever seen before. Major innovations are anticipated in virtually every industry and public sector.
The military has intense interest in nanotechnology to create better materials, more durable armaments, widely dispersed sensing systems, and robust communications systems. It believes that nanotechnology will alter warfare more than the invention of gun powder. The Department of Defense (DoD) has supported nanotechnology research for over two decades and expects to spend $243 million on it this fiscal year.
In 1986, researcher and author K. Eric Drexler introduced the term nanotechnology in his book Engines of Creation. The book describes anatomically precise molecular manufacturing systems and their products. Drexler also is the cofounder and chairman of the Foresight Institute, a nonprofit educational organization consisting of leading scientists whose goal is to help prepare society for anticipated advanced technologies.
But the idea for nanotechnology really dates back to late 1959, when physicist and Nobel Laureate Richard Feynman gave an invited talk to the American Physical Society's annual meeting. His noted speech, "There's Plenty of Room at the Bottom," described the challenges of manipulating and controlling things on a very tiny scale of molecules and atoms. This can be considered the dawn of the present-day vision of nanotechnology.
The original visionaries and many present-day researchers view nanotechnology from a bottom-up perspective, concentrating on a better understanding of the chemical, biological, and quantum properties of atoms and molecules of all types of materials, not just silicon. However, the inevitable march of semiconductor technology with its top-down approach of squeezing smaller and smaller features into a given area also is ongoing.
Like it or not, IC designers are being forced to solve these very issues addressed by the bottom-up group of researchers. They also face the increasing costs of lithographically fabricating ever smaller silicon devices. In fact, many bottom-up proponents warn that eventually we must move away from semiconductor lithography and find new ways to shrink things because it doesn't look like existing planar technology can get us down to the molecular precision levels being sought.
Ken Smith, vice president for technology at Carbon Nanotechnologies Inc., shares some of these views. "If the apparent promise of nano-electronics continues to be strong during the next decade, a growing number of engineers will have to develop new design paradigms required for circuitry that are truly different from those developed during the 'silicon age' of the last 50 years," he says. Smith anticipates that these new design paradigms will rely on what has been learned from silicon fabrication and will use some of the same approaches while adding others to deal with circuitry in which the active elements and interconnects are nanometer dimensions.
Meyya Meyyappan, director of nanotechnology for NASA's Ames Research Center, is even more vociferous on this point: "The most important and major challenge to realizing commercially available nanodevices is to overcome material problems. That means designers must look at what architectures to use. Continuing with conventional CMOS processes will get very expensive. The true realization of nanotechnology will only happen if we come up with novel process solutions, the so-called bottom-up assembly approach, instead of using just IC lithography alone."
As a good example, Meyyappan cites the bottom-up approach that Hewlett-Packard Labs is taking under the direction of scientist Stan Williams. Meyyappan is committed to addressing this bottom-up issue with electronics designers at every conceivable meeting he will speak at.
"Most nanotechnology researchers come from the chemical field and view things with a chemically oriented mindset," says James Von Ehr II, founder, chairman, and CEO of Zyvex Inc. "They say self-assembly is the only way to work in the nano field, and that's how they've learned it from chemistry. We're approaching it from the standpoint of engineers and software specialists as well as chemical and biological knowledge. We're looking to engineer improved subsystems, independently of one another, then tie them all together for a more useful solution."
Zyvex is one of the few companies, if not the only one, that employs both the bottom-up and top-down approaches. "Nanotechnology will make possible self-assembling systems using parallel nano-assemblers and hundreds of manipulators to handle nanocomponents," says Von Ehr. "Adaptable, affordable, and molecularly precise self-assembling manufacturing, the Holy Grail of nanotechnology, would become a reality."
Zyvex's present plan is to produce a family of nanomanipulation systems that can be used as flexible, cost-effective modular R&D tools that are compatible with scanning-electron microscopes (SEMs), transmission-electron microscopes (TEMs), optical microscopes, and probe stations. In fact, it has just introduced such a system, the S100, that will allow researchers to assemble, characterize and test nano structures and materials.
Philip Wong, senior manager of nano-scale materials, processes, and nano-scale devices at IBM's T.J. Watson Research Center, sees a natural ongoing evolution from the semiconductor age to the atomic and molecular realm. "By and large, nano-electronics is a continuation of the semiconductor revolution we've seen over the last 30 years. I see a gradual migration to atomic- and molecular-scale devices over the next couple of decades that will provide us with unique components for more versatile and precise self-assembly and improved materials," he says.
THE IMPORTANCE OF BEING PRECISE
"Precision" is a word often heard from many chemistry-oriented and physics-oriented scientists working the nanotechnology field. "The ultimate goal is to be able to accurately arrange atoms and molecules in most of the ways permitted by physical law, and to do so inexpensively," says Ralph Merkle, vice president for technology assessment at the Foresight Institute and winner of the 1998 Feynman Prize in Nanotechnology for Theory. "The trend toward greater precision will eventually take us to the point where we'll deal with the highest levels of precision. The trend to flexibility will give us the most flexible manufacturing systems. And the trend toward lower cost will lead us to a point where the manufacturing costs are not that much greater than the costs of the raw materials and energy used in the manufacturing process."
However, Merkle cautions that a more focused effort in atomic and molecular nanotechnology is needed before many rosy predictions are realized. By way of analogy, he points to Charles Babbage's development of the stored-program computer, which sat on the shelf for a very long time due to a lack of a focused effort.
"In the 1830s, Babbage developed what he called the analytical engine but what we'd call a stored-program computer," says Merkle. "He even described how it worked, giving it his equivalent terms to our present terms of op codes, operations, memory, and CPU. Unfortunately, it wasn't until more than a century later that work resumed on a stored-program computer."
LOOKING AT NANOTECHNOLOGY'S FUTURE
All of these developments bode well for nanotechnology, which is receiving record levels of funding from governments, industry, and academic circles (see "Funding for Nanotechnology Skyrockets," p. 56).
At a system level, most nanotechnology researchers foresee nano-scale particles that could be assembled into a world of tiny computers that can be embedded everywhere, including the human body, to improve every aspect of our lives. They're trying to harness the power of atoms and molecules to do useful work, just like trees that grow by using basic elements of light, water, and nutrients in the soil to make leaves, food, and wood. The issue of nano-assembly is receiving considerable attention at leading technical conferences, seminars, workshops, and in technical literature (see "Upcoming Nano-Assembly Technical Conferences," below).
It's not just small companies like Zyvex that are attempting to make inroads into nanotechnology. Major companies are getting into the action, too, with large budgets and R&D efforts. They include IBM, Hewlett-Packard, Intel, Motorola, NEC, Samsung, Siemens, Infineon, and Lucent Technologies. Moreover, just about every university worldwide has an aggressive nanotechnology R&D endeavor.
Broadly speaking, both mechanical and electrical properties, superior to anything known so far, are being investigated in nanotechnology. Researchers aim to improve these properties to build better materials, devices, and systems, like the self-assembly systems previously mentioned. Improved materials, catalysts, filters, fuel cells, solar cells, batteries, photonics, magnetics, sunscreen lotions, and sensor-dust networks have already been demonstrated using nanotechnology materials and devices.
Filters represent a very large area, using nanomaterials for all sorts of purification and cleaning. Nanotechnology also has potential as an alternative power source using fuel cells.
One of the most fundamental materials under scrutiny is carbon nanotubes (CNTs)—in both the single- and multiwalled varieties. A third form of carbon that belongs to the fullerene family, CNTs offer very desirable properties when properly processed. They feature high surface-to-volume ratios, small size, and high sensitivity. CNTs exhibit excellent mechanical strength superior to steel, excellent mechanical stability, better thermal conductance than a diamond, very high current densities of up to 1010 A/cm2 (copper melts at 107 A/cm2), and extremely high conductivity and electrical resistance that's independent of their length. Some 100,000 Å thinner than a human hair, CNTs can be metallic or semiconducting. With such characteristics, they offer amazing possibilities for creating future nanoelectronic devices, circuits, and computers (Fig. 1).
Two main processing methods exist for making CNTs: electric-arc discharge and laser ablation. Both are difficult to combine with semiconductor processing and don't scale up well. But they're useful for those working from the bottom up like Carbon Nanotubes Inc., NEC, and Samsung.
Infineon Technologies has developed a multiwalled CVD process that doesn't use plasma enhancement. The company implemented this process to make multiwalled CNTs at lithographically defined locations and claims it's compatible with semiconductor processing.
PLENTY OF ELECTRONIC DEVICES
A slew of applications awaits nanotechnology, including nonlithographically produced nanowires, electrical vias, CNT-based field-emission cathode materials, nano-based displays, nano-based biomedical systems, memories, logic elements, transistors, and quantum-dot computers.
Nano-scale, very high-density memory is one of the most exciting areas of investigation. Memories with densities well over 1 Tbit/in.2 have been demonstrated (Fig. 2, Fig. 3). So have organic transistors an order of magnitude smaller than those produced to date.
Very powerful yet tiny molecular and quantum-dot computers will also usher in unprecedented levels of computational power. Right now, special nano-scale materials and dyes are under investigation for high-performance outdoor displays.
Last month, NASA's Ames Research Center announced a new chemical process for the creation of thin CNTs—about 100 nm in diameter and 3 µm high. It involves growing microscopic whisker-like CNTs on the surface of a silicon wafer. The CNTs can replace copper for on-chip interconnections. "We think this process will help sustain the Moore's Law growth curve," says NASA's Meyyappan.
All nanotechnology researchers are very excited about biomedicine and eagerly await more powerful and effective nano-based drugs, surgical and analytical tools, healthcare systems, human genomics, and so forth. CNTs are being used here on silicon bio chips to identify DNA and protein molecules. Combining new hybrid nano-scale materials, both biological like DNA proteins and nonbiological like polymer plastics, provides the biomedical world with instruments and drug-delivery systems.
Zyvex's Von Ehr points to some exciting strides being made in the biomedical field, where researchers have taken Carbon 60 Buckeyballs and functionalized them with a little molecule on the side to block a person's susceptibility to the HIV disease. According to Von Ehr, field trials are presently being conducted on this development.
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