Moore's Law won't last forever. At some point, the physical laws that govern the behavior of transistors will make it impossible to keep...

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SAN JOSE, Calif. — Moore’s Law won’t last forever. At some point, the physical laws that govern the behavior of transistors will make it impossible to keep doubling the number of transistors on a single chip every couple of years.

The industry is trying to postpone the day of reckoning for at least 15 more years. But many experts believe silicon will eventually have to be replaced as the key material of computer chips to keep processing power growing at rapid rates.

“Any exponential extrapolated far enough predicts disaster,” said Intel co-founder Gordon Moore, who first made the prediction known as Moore’s Law. “The fact that materials are made of atoms will be a fundamental limit. We can’t go smaller than that.”

If the industry fails to find a solution and Moore’s Law falls off track, the consequences could be devastating for the $1 trillion electronics industry, which relies on chips getting cheaper and more powerful to drive improvements in the capabilities of everything from televisions to cellphones.

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The roots of the problem lie in the nature of silicon-based transistors, the tiny switches that turn the flow of electrons on and off in a circuit, creating the ones and zeroes that are the basis of electronic information.

Now that there are more than a billion transistors printed on a half-inch-square silicon chip, it’s getting harder to lay them down in the microscopic patterns that drive the chip’s functions. The lines separating the circuits are already smaller than the point of the sharpest tools available to draw and shape them.

Chip makers are also having trouble creating the insulation layers that separate the wires within transistors, since those layers are now only just a few atoms thick. And the packed-in transistors can generate enough heat to melt the entire chip.

The end of Moore’s Law has been forecast before, and each time the collective ingenuity of the $213 billion-a-year chip industry has come to the rescue with a technological solution to extend the capabilities of silicon chips.

But Moore and others admit they are getting more worried because there are more physical barriers standing in the way as manufacturing gets close to manipulating individual molecules.

At that level, a few atoms out of place could ruin an entire chip.

Bernie Meyerson, an IBM vice president, said alternatives to silicon will have to be found by 2020. Nanotechnology, a radically different approach to manufacturing on an atomic scale, offers the best potential for tools and materials that could enhance or replace silicon.

Traditionally, chip makers take a bulk material and winnow it down into a structure that they want. With nanotechnology, scientists envision starting with individual molecules and getting them to assemble themselves into larger electronic structures that can do the equivalent of what a chip does, which is store data or turn a switch on or off.

Governments are pouring $10 billion a year into nanotechnology research, but it may not be enough. “If we want to be in business by 2020, we have to start on it now,” said Paolo Gargini, a technical fellow at Intel.

In the short term, the industry will turn to a new type of insulator, known as a high-k dielectric insulator, to improve the power efficiency of silicon. Chip makers are also working on a way to write smaller patterns on chips. One research consortium has spent several hundred million dollars on extreme ultraviolet lithography, which will use mirrors and other methods to bend light to make writing patterns possible at tiny dimensions.

Looking out to 2010 or 2015, offshoots of nanotechnology could become useful to extend silicon’s usefulness. For instance, since 1991, scientists have been exploring carbon nanotubes, which are long sheets of graphene rolled into tube-like wires. These nanotubes can conduct electricity and are so thin they could replace today’s chip wiring, but so far, they are difficult to control.

In the long term, around 2020, true alternatives to silicon could materialize from current research into optical computing, which harnesses light to do calculations. Other promising experimental technologies include quantum dots, which are tiny switches that can be manipulated with a single electron, and spintronics, which exploits magnetic technology.

Moore himself is skeptical that the traditional methods for manufacturing chips will be replaced anytime soon.

“You can clearly make a tiny little transistor with potentially a very high frequency,” he said recently. “But can you connect a billion of them together? That’s really the problem.”

Economics may kill off Moore’s Law before technology does, said Bill Joy, a co-founder of Sun Microsystems and now a venture capitalist. Chip factories cost as much as $3 billion.