Trend of continuous improvement in computer chips may be ending

SAN FRANCISCO -- For more than three decades, Moore's Law has been an unshakable principle for the computer industry: every 18 months, the number of transistors that will fit on a silicon chip doubles.

Named for semiconductor pioneer and Intel co-founder Gordon Moore, who first stated it in 1965, the phenomenon has been the foundation of the computer revolution and the rise of the Internet. As transistors have been scaled ever smaller, computing performance has risen exponentially while the cost of that power has been driven down. And it has been assumed in the industry that the rate of progress would hold for at least another 10 to 15 years.

But now a researcher at Intel, the world's leading chip company, has reported glimpsing a potentially insurmountable barrier to the advance of Moore's Law much closer at hand, perhaps early in the coming decade.

In an article in the journal Science, the Intel scientist, Paul A. Packan, says it is not clear whether the most common type of silicon transistor can be scaled down beyond the generation of chips that will begin to appear next year, because semiconductor engineers have not found ways around basic physical limits.

"These fundamental issues have not previously limited the scaling of transistors," he wrote in the Sept. 24 issue. "There are currently no known solutions to these problems," he added, calling it "the most difficult challenge the semiconductor industry has ever faced."

Dennis Allison, a Silicon Valley physicist and computer designer, said: "The fact that this warning comes from Intel's process group is really significant. This says that they see actual limits."

The report by the Intel scientist will be echoed by researchers from the University of Glasgow in a paper to be presented in December at a conference in Washington.

Without further advances in the miniaturization of silicon-based transistors, hopes for continued progress would have to be based on technologies that are promising but unproved: new materials, new transistor designs and advances like molecular computing, in which single molecules act as digital on-off switches.

In the last decade, the advances described by Moore's Law have had an accelerating impact on the personal computer industry, driving the cost of desktop machines down from $3,000 to as low as $500 while increasing their power.

But for the first time the global semiconductor industry is grappling with transistors so small that the placement of individual atoms will soon become crucial.

For example, in the current generation of semiconductors, the wires that interconnect transistors are etched as fine as 0.18 micron -- 1/500 the width of a human hair -- and the individual insulating layers that are inside a transistor may be only four or five atoms thick.

Semiconductor factories in Japan plan to begin mass production of chips based on widths of 0.13 micron early next year, and such chips should be in widespread use within two years. But beyond that generation, the industry's leading researchers acknowledge there remain far more questions than answers.

The next step would be widths of 0.1 micron, a milestone that in the Moore's Law progression would be expected three to five years from now. But at that scale, Packan writes, transistors will be composed of fewer than 100 atoms, and statistical variations in this Lilliputian world are beyond the ability of semiconductor engineers to control.

Packan said he had written the Science article to challenge the industry and academia to focus on areas where breakthroughs are needed. "For the last 30 years we've been engineering the device, and now what's required is fundamental science," he said in a telephone interview.

Intel executives cautioned against reading too much gloom into their technical papers, saying that while they did not yet have precise engineering solutions for breaking the 0.1 micron barrier, they were confident that answers would be found.

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