Gordon Moore, a founder of the Intel Corporation, in a photograph from the late 1960s. In 1965, in what came to be called Moore’s Law, Dr. Moore laid out the principle that the number of transistors that could be etched on a chip would double annually for at least a decade.Credit Intel
When you’re thinking that big, bumping into the limits of physics could be a most humbling experience.
“I think the most fundamental issue is that we are way past the point in the evolution of computers where people auto-buy the next latest and greatest computer chip, with full confidence that it would be better than what they’ve got,” Dr. Colwell said.
The Limits of Physics
Chips are made from metal wires and semiconductor-based transistors — tiny electronic switches that control the flow of electricity. The most advanced transistors and wires are smaller than the wavelength of light, and the most advanced electronic switches are smaller than a biological virus.
Chips are produced in a manufacturing process called photolithography. Since it was invented in the late 1950s, photolithography has constantly evolved. Today, ultraviolet laser light is projected through glass plates that are coated with a portion of a circuit pattern expressed in a metal mask that looks like a street map.
Each map makes it possible to illuminate a pattern on the surface of the chip in order to deposit or etch away metal and semiconducting materials, leaving an ultrathin sandwich of wires, transistors and other components.
The masks are used to expose hundreds of exact copies of each chip, which are in turn laid out on polished wafers of silicon about a foot in diameter.
Machines called steppers, which currently cost about $50 million each, move the mask across the wafer, repeatedly exposing each circuit pattern to the surface of the wafer, alternately depositing and etching away metal and semiconducting components.
A finished computer chip may require as many as 50 exposure steps, and the mask must be aligned with astonishing accuracy. Each step raises the possibility of infinitesimally small errors.
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“I’ve worked on many parts of the semiconductor process,” said Alan R. Stivers, a physicist whose career at Intel began in 1979 and who helped introduce a dozen new semiconductor generations before retiring in 2007. “By far, lithography is the hardest.”
To build devices that are smaller than the wavelength of light, chip makers have added a range of tricks like “immersion” lithography, which uses water to bend light waves sharply and enhance resolution. They also have used a technique called “multiple pattern” lithography, which employs separate mask steps to sharpen the edges and further thin the metal wires and other chip components.
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The Westmere Die, a processor introduced by Intel in 2010.Credit Intel
As the size of components and wires have shrunk to just a handful of molecules, engineers have turned to computer simulations that require tremendous computational power. “You are playing tricks on the physics,” said Walden C. Rhines, chief executive of Mentor Graphics, a Wilsonville, Ore., design automation software firm.
If that scaling first described by Dr. Engelbart ends, how can big chip companies avoid the Moore’s Law endgame? For one, they could turn to software or new chip designs that extract more computing power from the same number of transistors.
And there is hope that the same creativity that has extended Moore’s Law for so long could keep chip technology advancing.
If silicon is, in the words of David M. Brooks, a Harvard University computer scientist, “the canvas we paint on,” engineers can do more than just shrink the canvas.
Silicon could also give way to exotic materials for making faster and smaller transistors and new kinds of memory storage as well as optical rather than electronic communications links, said Alex Lidow, a physicist who is chief executive of Efficient Power Conversion Corporation, a maker of special-purpose chips in El Segundo, Calif.
There are a number of breakthrough candidates, like quantum computing, which — if it became practical — could vastly speed processing time, and spintronics, which in the far future could move computing to atomic-scale components.
Recently, there has been optimism in a new manufacturing technique, known as extreme ultraviolet, or EUV, lithography. If it works, EUV, which provides light waves roughly a tenth the length of the shortest of the light waves that make up the visible spectrum, will permit even smaller wires and features, while at the same time simplifying the chip-making process.
But the technology still has not been proved in commercial production.
Earlier this year ASML, a Dutch stepper manufacturer partly owned by Intel, said it had received a large order for EUV steppers from a United States customer that most people in the industry believe to be Intel. That could mean Intel has a jump on the rest of the chip-making industry.
Intel executives, unlike major competitors such as Samsung and Taiwan Semiconductor Manufacturing Company, or TSMC, insist the company will be able to continue to make ever-cheaper chips for the foreseeable future. And they dispute the notion that the price of transistors has reached a plateau.
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Yet while Intel remains confident that it can continue to resist the changing reality of the rest of the industry, it has not been able to entirely defy physics.
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