Nanotechnology: Embrace the Future

To an industry that has been working in the angstrom regime for many years, the recent emphasis on "nanotechnology" as a science unto itself is almost a joke. It's true that today's nanotechnologists are working at the molecular level, but that's nothing new for the semiconductor industry. Almost from the beginning, the behavior of individual atoms and molecules has been an issue during ion implantation, deposition, etching, gettering and many other processes. Even from the standpoint of fabricating individual structures, gate dielectrics now measure ~5-10 nm, and critical linewidths will soon be below 100 nm. Surely that must be considered "nano" technology.

But to think that what's going on in nanotechnology is merely an extension of past semiconductor work would be wrong. Nanotechnology, probably best defined in the United States by the National Nanotechnology Initiative (NNI), represents a clear break from conventional thinking. The NNI defines nanotechnology in this way:

"Research and technology development at the atomic, molecular or macromolecular levels, in the length scale of approximately 1-100 nm range, to provide a fundamental understanding of phenomena and materials at the nanoscale and to create and use structures, devices and systems that have novel properties and functions because of their small and/or intermediate size. Nanotechnology research and development includes manipulation under control of the nanoscale structures and their integration into larger material components, systems and architectures. Within these larger scale assemblies, the control and construction of their structures and components remains at the nanometer scale. In some particular cases, the critical length scale for novel properties and phenomena may be under 1 nm (e.g., manipulation of atoms at ~0.1 nm) or be larger than 100 nm (e.g., nanoparticle reinforced polymers have the unique feature at ~200-300 nm as a function of the local bridges or bonds between the nanoparticles and the polymer)."

Although very broad in scope, including such things as nanoparticles used in sunscreens and applications in medicine, there's naturally a strong focus on electronics. One good example of nanotechnology work that might prove to be a cornerstone of future electronics technology is the carbon nanotube. Already, researchers at IBM have produced arrays of carbon nanotube transistors, and built a logic-performing computer circuit within a single molecule from a carbon nanotube (see Semiconductor International, October 2001).

Another good example is the recent work at Hewlett-Packard and UCLA, where wires of erbium were grown on a silicon substrate and used to "switch" molecules called rotaxanes, whose resistivity in the "on" state is 80-100× less than in the "off" position (see "Molecular-Level Nanowires Formed with Erbium"). Using this approach of chemical self-assembly instead of traditional lithography, researchers believe they could produce a prototype molecular computer in five years, and something you might imagine buying in 10 years.

That's not just idle speculation. "I often say nature's been good to us. The very first molecules we tried, these rotaxanes, actually worked. It could have taken years to find the right molecule," said Phil Kuekes of HP. "Another example is that we thought we might make rectangular wires with the erbium disilicide, and they ended up being very long."

Although now working at the nanoscale level, the semiconductor industry has relied on the same basic technology since its inception, where silicon-based transistors and interconnects are patterned with lithography. Someday — perhaps in about 10 years or so — that approach will run out of steam. Presumably, the industry will then turn to "new" technologies like carbon nanotubes and chemical self-assembly (or, heaven forbid, optical computing). If nature continues to be good to nanotechnologists, however, a viable alternative could be found sooner rather than later.

What do you think?