What are carbon nanotubes?

The conventional way to boost chip speeds is to shrink them. Intel’s latest roadmap states that semiconductors using the 10nm process will arrive by 2017, keeping Moore’s law on the technology statute book for at least another couple of years.

However, the long-term prospects of Gordon Moore’s prophecy are under threat, as the silicon transistors used in chips today will soon hit their limits. Intel has already stretched its release “cadence” from two years to two and a half, as it struggles to shrink the process even further.

Moore’s law now hinges on a replacement being found for silicon. IBM believes that could be carbon nanotubes, with a paper in Science revealing a major breakthrough that could eventually replace silicon transistors.

What are carbon nanotubes?

To make a carbon nanotube, simply take single-atom-thick sheets of carbon and roll them into tubes – it’s essentially a reinforced version of graphene. Ta-da, you’re a materials scientist. Of course, it’s easier said than done, and manufacturing is a problem. However, the tiny tubes can be used to make small transistors for use in chips for miniscule devices. Plus, carbon nanotubes require less energy to switch state than silicon, so devices using the technology require less power.

And what has IBM come up with?

IBM’s researchers have found a new way of connecting carbon transistors to contacts, which are valves that manage the flow of electrons into the semiconductor. The smaller the contact, the larger the electrical resistance, which slows everything down. That led to a performance bottleneck at sizes below 10nm. Researchers have found a way to chemically weld carbon nanotubes to the metal atoms of the contacts using molybdenum, which allows their size
to be shrunk along with transistors, without hurting performance.

So welding is cutting-edge science now?

If the welding sounds rather unimpressive, remember it’s on a microscopic scale. IBM has managed to weld carbon nanotube to contacts measuring 9nm. Not quite the same as fiddling with a soldering iron.

How tiny are we talking?

IBM has previously unveiled a 9nm carbon nanotube transistor, but the latest breakthrough takes it down to 7nm – with the potential long-term ability to shrink as small as 1.8nm, keeping Moore’s law ticking for many years to come. For comparison’s sake, Intel’s latest Skylake chips are made on a 14nm process, with the next generation shrinking to 10nm. To put that into a vaguely understandable sense of scale, 10nm is about 10,000 times thinner than a human hair.

How long until chips go carbon?

Chips will be made from silicon for many years to come. To make the switch to carbon nanotubes happen, IBM must figure out how to purify carbon so that only semiconductor molecules are left, and how to better work with nanotubes to transform them into chips. Then, when it’s ready, production factories can be built and devices can be designed to use the new chips. Those hurdles aside, IBM believes carbon nanotube technology could be in use within the decade – and it’s investing $3 billion to develop this “post-silicon” future.

Images: Masakazu Matsumoto and AJ Cann used under Creative Commons