Densest IC ever made

[Andre Kesteloot]

  International Herald Tribune <http://www.iht.com>
A tiny package with punch: Scientists create the densest chip ever
By Kenneth Chang
Thursday, January 25, 2007
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Scientists have built a tiny memory chip that uses new technology to 
pack a relatively large amount of information into a square about 
one-2,000th of an inch on a side.

Although the chip is modest in capacity --- with 160,000 bits of 
information --- the bits are crammed together so tightly that it is the 
densest chip ever made.

The achievement points to a possible path toward continuing the 
exponential growth of computing power even after current silicon 
chip-making technology hits fundamental limits in 10 to 20 years.

The scientists, led by James Heath of the California Institute of 
Technology and Fraser Stoddart of the University of California, Los 
Angeles, reported their findings in the issue of the journal Nature 
dated Thursday.

The density of bits on the chip --- about 100 billion per square 
centimeter --- is about 40 times that of current memory chips, Heath 
said. Improvements to the technique could increase the density by a 
factor of 10, he said.

As far back as 1999, Heath and Stoddart reported on aspects of their 
work, which included switches made of molecules and a novel technique 
for making ultrathin wires.

"Our goal always was to develop a manufacturing technique that works at 
the molecular scale," said Heath, a professor of chemistry. "It's a 
scientific demonstration, but it's a sort of a stake in the ground."

But Heath said he did not know if this technique would be commercially 
useful. "I don't know if the world needs memory like this," he said. "I 
do know if you can manufacture at these dimensions, it's a fundamentally 
enabling capability."

A critical component of the chip is its molecular switch, designed by 
Stoddart.

The switch, which belongs to a class of molecules known as rotaxanes, 
looks like a dumbbell with a ring that can slide along the central bar. 
Voltage pulses push the ring between two positions on the bar, which 
represent the zeros and ones used by computers to store data. The 
dumbbell shape keeps the ring from sliding off.

To build the chip, the researchers etched 400 parallel wires, each with 
of width of less than less than a millionth of an inch, or 0.000024 
millimeters, and separated by about one-750,000th of an inch from its 
neighbors.

On top of the wires, they deposited a layer of the molecular switches, 
the dumbbells standing vertically, and then a second set of 400 wires 
turned 90 degrees to the first set.

Each crossing point between two perpendicular wires, with about 100 of 
the molecular switches wedged in between, is the storage location of one 
bit of information.

While many researchers are looking for ways to make molecular-size 
electronics, most are still building circuits containing only a handful 
of bits, compared with the 160,000 in the new chip.

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