[TWIAR] H-P proposes alternative to transistors

[Greg Williams]

Crossbar latches of metal and molecules but no silicon

Eric Risberg / AP

Three researchers at Hewlett-Packard have demonstrated a technology that
dwarfs transistors and could replace them in computers.  

The Associated Press

Updated: 3:00 p.m. ET Feb. 1, 2005

SAN JOSE, Calif. - Challenging a basic tenet of the semiconductor
industry, researchers at Hewlett-Packard Co. have demonstrated a
technology that could replace the transistor as the fundamental building
block of all computers.

The devices, called crossbar latches, could be made so small that
thousands of them could fit across the diameter of a human hair,
enabling the high-tech industry to continue to build ever-smaller
computing devices that are less expensive than their predecessors.

For years, engineers have been able to pack more and more smaller
transistors onto a fingernail-size silicon chip.  The rate of
integration, first predicted by Intel Corp. co-founder Gordon Moore in
1965, has driven computer performance and prices for more than 30 years.

But the pace of Moore's Law can't continue forever, and the high-tech
industry has been scrambling to develop workarounds for the day —
expected in a decade or so — when transistor dimensions become too small
for the materials commonly used today.

"If we're going to extend Moore's Law for another several decades, we've
got to have an alternative strategy," said Phil Kuekes, one of the
paper's authors at H-P Labs.  "This is the final piece of the puzzle in
what H-P has been putting together as such a strategy."

The smallest features of today's silicon-based transistors are about 90
nanometers long, a nanometer being roughly one hundred-thousandth the
width of a human hair.  The crossbar latch, by comparison, can work in a
space of about 2 to 3 nanometers.

The H-P research, reported in Tuesday's Journal of Applied Physics,
scraps the transistor entirely.  In its place is basically a series of
platinum wires crossed opposite directions.  At the junctions are
molecules that in the H-P research happen to be steric acid.  "It's
metal and molecules.  Nothing else," Kuekes said.  "We're getting away
from the physics of silicon."

Like in a transistor, an electrical signal that passes through a
crossbar latch is manipulated to perform logic functions.  The latest
research shows that the technology also can be used for amplifying a
signal, allowing multiple functions to be applied.

"The power of this device is not when it's by itself. It's when it glues
together other pieces of logic," said Duncan Stewart, another H-P Labs
scientist and study co-author.  "As soon as you're able to do that, we
call that a computer."

The researchers have not glued together multiple crossbar latches,
though they say it's something they're continuing to pursue.  They
expect it to be commercially viable as early as 2012.  The latches are
formed through a specialized stamping process for nano-sized imprints.

They also must persuade an industry built on transistors that an
alternative technology can be just as effective, said Stan Williams,
director of Quantum Science Research at H-P Labs and another of the
paper's co-authors.

"There came to be a mantra that you have to have transistors to build
computers," he said.  "A latch is a different way of achieving that same
function, but it turns out it has significant advantages over a
transistor."

Do more
The crossbar latch not only works at a much smaller scale than a
transistor but also can do more, he added.  "In order to do the same
thing that a latch can do, you actually need many transistors," Williams
said.

In fact, other researchers have been focused on building molecular
transistors, which are much more challenging to build at such a small
scale, said James C. Ellenbogen, principal scientist in the Nanosystems
Group at the MITRE Corp.

"This may enable the field to proceed toward nanoprocessor
demonstrations and applications more rapidly and at lower cost," he
said.

It also could prove to be less expensive to build because engineers can
more easily work around defects that arise during manufacturing than
with those that occur during silicon fabrication, where defects are
avoided at great cost.

But crossbar latches aren't going to replace today's silicon chips
anytime soon.  At first, they would likely be used for memory and later
for specialized devices.  They also will have to integrate with today's
silicon chips for the time being.

"Transistors will continue to be used for years to come with
conventional silicon circuits," Kuekes said, "but this could someday
replace transistors in computers, just as transistors replaced vacuum
tubes and vacuum tubes replaced electromagnet relays before them."

Gregory S. Williams
k4hsm at knology.net