IEEE Spectrum August, 2009 - 9

Eye on
the Prize
In late June a
coalition of research
teams announced
that it had qualified
for the US $1 million
prize that Netflix has
offered to whomever
improves its movie
recommender
system by at
least 10 percent.
"We haven't won
the million yet,
just crossed the
necessary threshold,
moving the
competition into
a 30-day 'last call'
period," says Yehuda
Koren of Yahoo
Research, a member
of the coalition.
Koren and two
colleagues at his
former employer,
AT&T Labs Research,
won an earlier stage
in the competition
(see "The Million
Dollar Programming
Prize," IEEE Spectrum,
May 2009). Koren
says his team would
reveal its latest
algorithmic tricks "if
and when we win."

16

Big flaw found in
transistor noise theory

E

ngineers at the U.S.
National Institute of
Standards and Technology
(NIST) say that the basic theory
explaining the origin of a certain
type of noise produced by very
small transistors is totally wrong.
Known as random telegraph
noise, this aberrant signal is
becoming a problem for static
RAM and flash memory, and it
will also become a threat to future
low‑power logic circuits as their
dimensions continue to shrink and
the voltage at which they operate
decreases. Without a theory,

engineers will find it difficult to
reduce the noise, predicts Jason
Campbell, a National Research
Council postdoctoral fellow at
NIST. "If you don't know where
it's coming from, you don't
know how to fix it," he says.
"It's critical to raise this issue,"
says Genadi Bersuker, a fellow at
Sematech in Austin, Texas. "The
whole spectrum of processes
involved in noise is much richer
than the simplified description
everyone tends to use."
The prevailing theory says
that as an electron passes
through the transistor's channel
it can temporarily get stuck in the
insulation above. That happens
because of a quantum mechanical
phenomenon called tunneling,
which makes it possible for
the electrons to jump through
the insulation as if it weren't
there. According to the theory,
electrons randomly tunnel into
defects in the insulation and

then tunnel out. The random
moving‑stuck‑moving pattern
was thought to cause the noise.
The duration of the tunneling
process is related to the thickness
of the insulation, and decades
ago, when the theories were
formulated, insulation was
micrometers thick. But now
it is measured in nanometers.
Campbell measured production‑
quality nanometer‑scale test
transistors, made by TSMC, that
were much smaller than those
in high‑end microprocessors
and whose insulation was
only 1.4 nm thick. He expected
to see tunneling that took
nanoseconds to picoseconds.
Instead, the process took the
milliseconds to seconds you'd
see in a much bigger transistor.
"What people thought is very
likely not correct," says Campbell,
who presented the results at two
IEEE‑sponsored conferences in
April and May. -Samuel K. Moore

Dinosaur Egg

Djemel Lellouchi, of
microelectromechanical
systems reliability firm
Nova MEMS, in Ramonville,
France, found this oddity
when investigating the failure
of an optical switch due to an
electrostatic discharge. The
image won the annual Art of
Failure Analysis photo contest
at the IEEE International
Symposium on the Physical and
Failure Analysis of Integrated Circuits, in Suzhou, China, from 6 to 10 July.
The egg was just one of many microscopic curiosities collected by failure‑
analysis experts this year, including a sulfide flower, a tungsten snake's tail,
and an infant's face on gold. For the top 10 entries, see http://www.spectrum.
ieee.org/slideshow/semiconductors/devices/slideshow‑the‑art‑of‑failure‑2009.

Na * IEEE spEctrum * august 2009

www.spectrum.ieee.org

Djemel lellouChi

news
briefs

Future of LowPower Chips
in Doubt
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Table of Contents for the Digital Edition of IEEE Spectrum August, 2009
