Due to the increasing complexity of the fabrication process, the price tag of a single semiconductor factory, or fab, could hit $10 billion by the decade’s end, up from $2 billion today.

In a dimly lit lab in Yorktown Heights, N.Y., the workbenches are crowded with scanning-tunneling microscopes, atomic force probes, and an assortment of other tools used to render the molecular world visible. There, at IBM’s (IBM ) Thomas J. Watson Research Center, Phaedon Avouris and his team are using these instruments to conquer the Everest of nanotechnology: They’re learning how to weave wisps of carbon, atom by atom, into working transistors. Advertisement

Avouris’ aim is to outrun a ticking clock. Since the dawn of the semiconductor industry a half-century ago, computer companies have depended on chipmakers to keep Moore’s Law on track, doubling the speed of their devices every 18 months. The chipmakers achieved this magic by packing transistors more closely together on ever-shrinking flecks of silicon. Tinier transistors run faster. But the chips also run hotter, and they become much more complicated to produce. As chip features shrink from 90 nanometers today toward 20 nm or 10 nm over the next decade, the burdens of heat, cost, and unruly physics could render silicon useless. If the industry doesn’t find an alternative, Moore’s Law will hit a brick wall.

EFFICIENT REPLACEMENT
The problems are already taking a toll. Today’s fastest PC chips run hot enough to cook an egg. If unchecked, the increase in heat is on track to hit metal-melting temperatures by decade’s end. That not only wastes power — as much as half the power consumed by today’s fastest processors may be lost as heat — but can also slow down or even damage a chip. “Chipmakers have to get away from multibillion-dollar fabs,” says Sam Brauer, a principal at Nanotech Plus LLC, a market consultant in Stamford, Conn. “It’s their Holy Grail.”



At IBM, Infineon, NEC, and a clutch of startups, the leading candidate to replace silicon is the ethereal carbon nanotube. This tiny molecule — 100,000 lined up side by side are about as thick as a human hair — promises to make circuits faster, less power-hungry, and more densely packed than anything possible today. And they could vastly simplify the way chips are made.



Even though such transistors are still in their infancy, says IBM’s Avouris, “Carbon nanotubes can get around most of the problems that doom very small silicon devices.” In the lab, he has backed this statement up. It took him four years to assemble his current, third-generation prototype of a carbon nanotube transistor, but in the end, the device can carry up to 1,000 times the current of the copper wires used in today’s silicon chips, making it vastly more efficient.



The nanotubes themselves are deceptively simple. Joined in superstrong hexagonal bonds, carbon atoms arrange themselves in a cylinder, like a coil of chicken wire. By changing the geometry of the tube’s honeycomb of atoms, researchers can tune them to resist or conduct electricity, which is one reason they can carry very high currents while emitting little heat. “Mixing together nanotubes with different electrical properties could simplify the design of future chips,” says Paolo A. Gargini, chairman of the International Technology Roadmap for Semiconductors, an industry planning consortium, and Intel Corp.’s director of technology strategy. It would eliminate many of the exotic chemicals and processes now used to make chips.



The virtues of nanotubes go beyond electricity. In addition to being excellent conductors of heat, the tubes are 10 times stronger than steel and are resistant to radiation. This matters because as chips get smaller, they are becoming more vulnerable to damage from high-energy solar particles. So, long before they replace transistors as the brains of chips, says Craig Sander, Advanced Micro Devices’ (AMD ) vice-president for technical development, carbon nanotubes are likely to be mixed in as part of the chip’s structural layer.



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