BY JOHN MARKOFF
New York Times
Saturday, October 9, 1999, the
San Jose Mercury News
SAN FRANCISCO -- For more than three
decades,
Moore's Law has been an unshakable
principle for the computer
industry: every 18 months, the
number of
transistors that will fit on a
silicon chip
doubles.
Named for semiconductor pioneer
and Intel
co-founder Gordon Moore, who first
stated
it in 1965, the phenomenon has
been the
foundation of the computer revolution.
As
transistors have been scaled ever
smaller,
computing performance has risen
exponentially
while the cost of that power has
been driven
down. And it has been assumed in
the
industry that the rate of progress
would hold
for at least another 10 to 15 years.
But now a researcher at Santa Clara-based
Intel, the world's leading chip
company, has
reported glimpsing a potentially
insurmountable barrier to the advance
of Moore's Law
much closer at hand, perhaps early
in the
coming decade.
In an article in the journal Science,
the
Intel scientist, Paul A. Packan,
says it is not clear
whether the most common type of
silicon
transistor can be scaled down beyond
the
generation of chips that will begin
to appear
next year, because semiconductor
engineers
have not found ways around basic
physical limits.
``These fundamental issues have
not
previously limited the scaling
of transistors,'' he
wrote in the Sept. 24 issue. ``There
are
currently no known solutions to
these
problems,'' he added, calling it
``the most
difficult challenge the semiconductor
industry
has ever faced.''
Dennis Allison, a Silicon Valley
physicist
and computer designer, said: ``The
fact that
this warning comes from Intel's
process group
is really significant. This says
that they
see actual limits.''
The report by the Intel scientist
will be
echoed by researchers from the
University of
Glasgow in a paper to be presented
in
December at a conference in Washington.
Need for new materials
Without further advances in the
miniaturization of silicon-based
transistors, hopes for
continued progress would have to
be based on
technologies that are promising
but
unproved: new materials, new transistor
designs and advances like molecular
computing,
in which single molecules act as
digital
on-off switches.
To be sure, such dire warnings have
been made
periodically in the past -- an
article in
Scientific American in 1987 said
Moore's Law
was unlikely to be maintained through
the
1990s -- and each time semiconductor
designers have shown remarkable
ingenuity to
surmount seemingly impossible barriers.
The inventors of the original semiconductor
design technology are for the most
part still
bullish about extending that progress,
whatever the immediate hurdles.
``Historically the economic incentives
to
find new methods for device improvement
have
regularly overcome the predicted
scaling
limits,'' said John Moussouris,
a physicist and
semiconductor designer. ``The physical
challenges may be getting harder,
but the people
and financial resources to surmount
them are
also growing each year.''
But for the first time the global
semiconductor industry is grappling
with transistors so
small that the placement of individual
atoms
will soon become crucial.
For example, in the current generation
of
semiconductors, the wires that
interconnect
transistors are etched as fine
as 0.18 micron
-- 1/500 the width of a human hair
-- and the
individual insulating layers
that are inside
a transistor may be only four or
five atoms
thick.
Semiconductor factories in Japan
plan to
begin mass production of chips
based on widths
of 0.13 micron early next year,
and such
chips should be in widespread use
within two
years. But beyond that generation,
the
industry's leading researchers
acknowledge there
remain far more questions than
answers.
The next step would be widths of
0.1 micron,
a milestone that in the Moore's
Law
progression would be expected three
to five
years from now. But at that scale,
Packan
writes, transistors will be composed
of fewer
than 100 atoms, and statistical
variations in
this Lilliputian world are beyond
the ability
of semiconductor engineers to control.
Packan said he had written the Science
article to challenge the industry
and academia to
focus on areas where breakthroughs
are
needed. ``For the last 30 years
we've been
engineering the device, and now
what's
required is fundamental science,''
he said in a
telephone interview Friday.
Intel executives cautioned against
reading
too much gloom into their technical
papers,
saying that while they did not
yet have
precise engineering solutions for
breaking the 0.1
micron barrier, they were confident
that
answers would be found.
`Serious challenges'
They suggested that part of the
reason for
Intel's recent pessimism might
have more to do
with the need for corporate secrecy
than the
arrival of fundamental technical
limits.
``We face serious challenges,''
said Mark
Bohr, an Intel technology development
director and co-author of an internal
Intel
technical paper that enumerates
the company's
unsolved problems. ``We all have
ideas to
address some of these problems
and
admittedly they are iffy and not
fully
developed, and you don't want to
tip your cards too
soon.''
And Carver Mead, a physicist and
a pioneer in
semiconductor design, says he still
adheres to what has been the conventional
industry wisdom, suggesting that
Moore's
Law will continue to account for
the pace of
silicon technology advances until
at least
2014. ``There are still some open
issues,''
he said. ``and so the Chicken Little
sky-is-falling articles are a recurring
theme.''
But James Heath, a chemistry professor
at the
University of California at Los
Angeles
who is a co-inventor of the Carbon
60
molecule known as the Buckyball,
said the
industry might be overly optimistic
because
it has such a vast investment in
today's
silicon technology.
With researchers at Palo Alto-based
Hewlett-Packard, Heath has developed
a prototype
memory cell the size of a single
molecule
that operates on different principles
than
today's semiconductors.
Unrealistic
``I think their optimism for
being able to
continue until 2014 is not very
realistic,'' he
said. ``When you get to very, very
small
sizes, you are limited by relying
on only a
handful of electrons to describe
the
difference between on and off.''
Executives at IBM, which along with
Intel and
Motorola is one of the nation's
dominant
chip makers, conceded that it may
be accurate
to warn of an impending limit to
the
shrinking of today's dominant chips,
known as
CMOs, or complimentary metal oxide
semiconductors. But they said they
believed
they had found an alternative approach,
known as silicon-on-insulator,
that held
great promise at dimensions of
0.1 micron and
smaller.
``This paper is quite consistent
with work
we've published,'' said Randall
Isaac, vice
president for systems technology
and science
at IBM's Watson Laboratory in Yorktown
Heights, N.Y. ``But when a given
technology
saturates, it is usually replaced
by a new
one.''
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