A group ofresearchers at MIT have developed a new modern microprocessor from carbon nanotubetransistors, which are widely seen as a faster, greener alternative to theirtraditional silicon counterparts.
A close up of a modern microprocessor built from carbon nanotube field-effect transistors. Credit: MIT
The microprocessor can be built using traditional silicon-chip fabrication processes and represents a major step toward making carbon nanotube microprocessors more practical.
Silicon transistors have carried the computer industry for decades. The industry has been able to shrink down and cram more transistors onto chips every couple of years to help carry out increasingly complex computations. But experts now foresee a time when silicon transistors will stop shrinking.
Makingcarbon nanotube field-effect transistors (CNFETs) has become a major goal forbuilding next-generation computers. Research indicates they have propertiesthat promise around 10 times the energy efficiency and far greater speedscompared to silicon. But when fabricated at scale, the transistors often comewith many defects.
Researchers at MIT have invented new techniques to dramatically limit defects and enable full functional control in fabricating CNFETs, using processes in traditional silicon chip foundries. They demonstrated a 16-bit microprocessor with more than 14,000 CNFETs that perform the same tasks as commercial microprocessors.
“This is by far the most advanced chip made from any emerging nanotechnology that is promising for high-performance and energy-efficient computing,” said co-author Max M. Shulaker. “There are limits to silicon. If we want to continue to have gains in computing, carbon nanotubes represent one of the most promising ways to overcome those limits.”
But the new carbon nanotube microprocessor isn’t ready yet to take over silicon chips. Each one is about a micrometer across, compared with current silicon transistors that are tens of nanometers across. Each carbon nanotube transistors in this prototype can flip on and off about a million times each second, whereas silicon transistors can flicker billions of times per second.
Shrinkingthe nanotube transistors would help electricity zip through them with lessresistance, allowing the devices to switch on and off more quickly. At the sametime, aligning the nanotubes in parallel, rather than using a randomly orientedmesh, could also increase the electric current through the transistors to boostprocessing speed.
The researchers have now started implementing their manufacturing techniques into a silicon chip foundry through a program by the Defense Advanced Research Projects Agency, which supported the research.
Although no one can say when chips made entirely from carbon nanotubes will hit the shelves, Shulaker says it could be fewer than five years.
