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The Tiniest Transistor

11 June 2001 7:00 pm
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Nanoswitch. This ultrasmall silicon transistor and a billion of its brethren may soon be in a computer chip near you.

Over the last few years, researchers have crafted transistors--the key ingredients of computer chips--with components that measure in the nanometers, or billionths of a meter. But no one has yet figured out a way to produce these ultratiny devices en masse. At a meeting yesterday in Kyoto, Japan, however, researchers from Intel unveiled a nanoscale transistor, made with techniques used in mass-producing computer chips today. The work promises to continue the 35-year trend of creating ever more powerful computer chips through the end of this decade.

The smallest transistors are made with a technique called electron beam lithography, which uses a narrow beam of electrons to carve features into the chips. The technique can pattern features smaller than 10 nanometers across, but it's far too slow for manufacturing.

By contrast, current computer chips are made with photolithography, in which ultraviolet (UV) light is shone simultaneously through millions of features on a stencil onto a silicon wafer coated with plastics that absorb the light. Chemical etchants then remove either the exposed or unexposed plastic and a layer of the silicon underneath. But this technique can only make features around 125 nanometers wide, about half the wavelength of the 248-nanometer UV light used.

The Intel team--led by electrical engineer Robert Chau--also used 248-nanometer light. But according to team member Rob Willoner, they managed to carve far more precise features than usual, using a series of "tricks" that he declined to describe. The smallest feature was a transistor component called a gate--an electrode that controls the flow of electric current in the device--just 20 nanometers long. Because it's so small, current inside the transistor travels an extremely short distance as the device is switched on or off, allowing for an unprecedented switching speed of 1.5 terahertz, or 1.5 trillion times a second.

"This is a very impressive result," says Sandip Tiwari, who directs the Cornell Nanofabrication Facility in Ithaca, New York. The tiny transistor isn't ready for the factory floor just yet: The device still leaks current even when switched off, a flaw that if duplicated millions of times could cause a computer chip to overheat. But Willoner says Intel expects to fix that and incorporate the devices into chips by 2007. At that time, the company plans to pack about 1 billion such devices on a single chip--25 times the number in today's top-of-the-line Pentiums.

Related site

'Silicon Showcase,' a Web site about transistors and chips by Intel

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