IBM breakthrough buys time for Moore’s Law

In a discovery that could further extend the life of Moore’s Law by allowing more transistors to be placed on a computer chip, IBM Corp. researchers have developed a transistor technology that permits the mass production of semiconductors that are smaller and faster and require less power than chips currently made out of silicon. The findings are contained in a scientific paper entitled “Engineering Carbon Nanotubes and Nanotube Circuits Using Electrical Breakdown,” published in the April 27 issue of Science.

Moore’s Law, originally posited by Intel Corp. co-founder Gordon Moore, states that the number of transistors that can be placed on a computer chip will double every 18 months. Although common wisdom holds that Moore’s Law will hold out for at least another 10 years, observers have pointed to the physical-size limitations of transistors built using silicon as an eventual limit to the number of transistors that can be placed on a chip.

However, according to a statement released by IBM, company researchers have built the world’s first array of transistors out of carbon nanotubes, tiny cylinders of carbon atoms that measure as small as 10 atoms across and are 500 times smaller than silicon-based transistors, using a batch process for forming large numbers of nanotube transistors. The smaller size of carbon nanotube semiconductors allows more transistors to be placed on a chip than is possible using silicon.

Previously, nanotubes had to be positioned one at a time or by random chance, which though feasible for scientific experiments is considered impractical for mass production, IBM said. The batch process, dubbed constructive deconstruction, overcomes a major obstacle in the production of carbon nanotubes, which can be either metallic or semiconducting, the company said.

Researchers had been unable to use carbon nanotubes as transistors because existing synthetic methods of production yield a mixture of metallic and semiconducting nanotubes that stick together to form ropes or bundles, IBM said. This compromises the usefulness of nanotubes, because only semiconducting nanotubes can be used as transistors and the metallic nanotubes overpower the semiconducting nanotubes, the company said.

Given this challenge, the obstacle to using semiconducting nanotubes has been the absence of a means to separate the metallic and semiconducting nanotubes on a scale that would be useful for mass production, said IBM. The constructive destruction technique achieves this by allowing scientists to produce semiconducting carbon nanotubes with the electrical properties required to build computer chips by destroying metallic nanotubes with an electric shock wave, leaving only the semiconducting nanotubes needed to build transistors, said the company.

IBM Corp., in Armonk, N.Y., can be reached at