SMALLER cellphones with better reception could be on the horizon, thanks to a
new microchip inductor that鈥檚 nearly three times as efficient as today鈥檚
devices, say researchers at the Korea Advanced Institute of Science and
Technology in Taejon. Their secret is to suspend the device in mid-air.
Cellphones need tuners and noise-filtering circuits, which include inductors:
conducting spirals that can be etched onto the surface of a semiconductor. The
efficiency of such devices is poor because current leaks from the conductor into
the chip.
Now Jun Bo Yoon and his colleagues at KAIST say they have solved the leakage
problem by hoisting the copper coil above the chip, creating an air gap. The
team will tell the International Electron Devices Meeting in Washington DC in
December how they made their inductors 鈥渇loat鈥� several hundredths of a
millimetre above the microchip鈥檚 base. The copper spiral is
deposited onto a substrate that is then etched away, save for some small support
posts.
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The filtering efficiency of an inductor is indicated by its quality factor
(Q). While today鈥檚 on-chip devices typically have a Q approaching 20, the new
device has a Q of up to 57. Peter Harrison, technology manager at Nokia, says
that efficient noise filtering in mobiles is essential. 鈥淎nd we would welcome
any new components that let us make smaller cellphones,鈥� he says.