MIT Researchers built a 16-bit carbon nanotube-based microprocessor that can accurately execute the full RISC-V instruction set. Employing newly invented techniques to mitigate material and manufacturing defects, the 14,000-transistor chip executed a classic Hello World program, as well as other tasks.
Because of their higher conductivity, carbon nanotubes might one day take the baton from silicon as the go-to semiconductor. A key obstacle, however, is the presence of metallic nanotubes, which ruin transistors. Even though present only in traces after careful synthesis and purification steps, there invariably are too much of them to build a working IC using conventional methods.
The MIT researchers overcame this problem by developing a design technique that positions the FETs in such a way that they don’t interrupt computing. Together with new techniques to prevent ‘clumping’ of the tubes and position them optimally on the wafer, it proved possible to assemble a processor consisting of over 10,000 transistors. The first carbon nanotube computer, built six years ago, only contained hundreds (link in Dutch).
“This is by far the most advanced chip made from any emerging nanotechnology that is promising for high-performance and energy-efficient computing,” says Max Shulaker, co-author of the paper published in Nature. “If we want to continue to have gains in computing, carbon nanotubes represent one of the most promising ways to overcome those limits. Our work completely re-invents how we build chips with carbon nanotubes.”