October 6, 2015 1:07:36 am
TECHNOLOGY: MAKING TRANSISTORS SMALLER
Published in Science, October 2, 2015
Authors: Qing Cao, Shu-Jen Han and Others
In the semiconductor business, it is called the “red brick wall” — the limit of the industry’s ability to shrink transistors beyond a certain size. However, IBM scientists reported last week that they now believed they saw a path around the wall. Writing in the journal Science, a team at the company’s Thomas J Watson Research Center said it has found a new way to make transistors from parallel rows of carbon nanotubes.
The advance is based on a new way to connect ultrathin metal wires to the nanotubes that will make it possible to continue shrinking the width of the wires without increasing electrical resistance.
One of the principal challenges facing chip makers is that resistance and heat increase as wires become smaller, and that limits the speed of chips, which contain transistors.
The advance would make it possible, probably some time after the beginning of the next decade, to shrink the contact point between the two materials to just 40 atoms in width, the researchers said. Three years later, the number will shrink to just 28 atoms, they predicted.
The ability to reduce electrical resistance will not only make it possible to extend the process of shrinking transistors beyond long-held beliefs about physical limits. It may also be the key to once again increasing the speed of computer processors, which has been stalled for the last decade.
The report represents a big advance for an exotic semiconductor material that has long held great promise but has also proved maddeningly difficult for scientists to work with. Single-wall carbon nanotubes are strawlike structures that are a composed of a one-atom thick matrix of carbon atoms rolled into an infinitesimally small tube.
The challenge of carbon nanotubes in their typical state is that they form what scientists call a giant “hairball” of interwoven molecules.
However, researchers have found ways to align them closely and in regularly spaced rows and deposit them on silicon wafers with great precision. They then serve the crucial role of a semiconductor, allowing electrical current to be switched on and off in a computer circuit.
Until now, however, they have been just one of a range of new materials that have been seen as candidates to replace silicon, which has for more than half a century been the material of choice for chip makers.
“Of all the possible materials, this one is at the top of the list by a long shot,” said Dario Gil, vice president for science and technology at IBM.
At the same time, he acknowledged that challenges remained in perfecting carbon nanotube transistors, but he said that IBM was increasingly confident that they could be overcome.
— JOHN MARKOFF, THE NYT
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