Researchers get Moore's Law to work at the atomic scale
Moore's Law may just survive quirky quantum effects to oversee the incredible shrinking procession of computer chips for years to come if a new study by Australian and American researchers is adaptable to large-scale silicon fabrication.
Ohm's law, which suggests that electrical resistivity should remain constant no matter the size of an electrical component, also appears to be safe.
It turns out that silicon wires just an atom tall and four atoms wide can maintain low electrical resistivity if put together just the right way, according to a research team led by Michelle Simmons of the Center for Quantum Computation and Communication Technology at the School of Physics of the University of New South Wales in Sydney, Australia.
Chip manufacturers like Intel have managed to shrink their products regularly for decades—doubling the circuitry on silicon wafers roughly every two years, as per Intel co-founder Gordon Moore's eponymous "law" —thanks to technological innovation and lower manufacturing costs.
But as the transistors that make up computer chips have shrunk to sizes approaching the atomic scale, a new challenge looms—extremely tiny chip components tend to resist the flow of an electrical current. Since computer chips use electricity to conduct their business, that's a major problem. In fact, scientists have found that once circuitry gets below 10 nanometers, its resistivity increases exponentially the smaller it gets.
Semiconductor manufacturers are already producing 22nm chips for release this year and the 10nm node should come online in 2015, as per Moore's Law. But to get even smaller, chip makers will have to figure out ways around the resistivity problem and other atomic-scale problems like quantum tunneling.
Enter Simmons and researchers from the University of New South Wales, the University of Melbourne, and Purdue University's Birck Nanotechnology Center. In a study
published in the current issue ofScience
, they say they've achieved ohmic scaling to the atomic limit—which is to say they've managed to get electrical wires just a few atoms in width to work the way they're supposed to.
The researchers embedded phosphorus atoms within a silicon crystal "with an average spacing of less than one nanometer," they report, to create wires with widths ranging from 1.5 to 11 nanometers. The resistivity exhibited by the wires, from skinniest to thickest, was roughly the same—a result that Simmons and her co-authors say could "pave the way for single-atom device architectures for both classical and quantum information processing."
The trick, however, will be to translate the experiment to large-scale manufacturing processes.
Simmons and her team basically hand-crafted their circuitry, "covering a silicon crystal with a layer of hydrogen atoms and then carving out several-nanometer-wide channels in the hydrogen using the tip of a scanning tunneling microscope," according to Nature
, which reviewed the Science
That's a far cry from the mass-production techniques used in modern semiconductor manufacturing, one skeptic told Nature. Penn State electrical engineer Suman Datta said that in practical chip production, it probably wouldn't be possible to use as much phosphorous as the researchers did, meaning resistivity would still increase as circuitry reaches the atomic scale unless another solution is found.
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source: Researchers Get Moore's Law to Work at the Atomic Scale