IBM Research Breakthrough: Nanotube Electronics Could Replace Silicon

The new result from IBM represents a “fantastic strategy” for addressing the contact problem, said Michael Arnold, a professor of materials science and engineering at the University of Wisconsin, who was not involved in the research.

Earlier this summer, IBM unveiled the first 7 nanometer node silicon test chip, pushing the limits of silicon technologies and ensuring further innovations for IBM Systems and the IT industry. As devices become smaller, increased contact resistance for carbon nanotubes has hindered performance gains until now.

If a breakthrough in carbon nanotube transistors from IBM Research pans-out, the hard stop of 2028 in worldwide Technology Roadmap for Semiconductors (ITRS) is about to get extended.

The company said that the breakthrough brings it closer to creating fully scaled carbon nanotube technology that will power future computing technologies while increasing performance and “opening a pathway to dramatically faster, smaller and more powerful chips”. IBM has developed a novel way, at the atomic level, to weld – or bond – the metal molybdenum to the ends of carbon nanotubes to create a completely new contact structure. The carbon nanotubes form the core of a transistor device whose superior electrical properties promise several generations of technology scaling beyond the physical limits of silicon. “This breakthrough shows that computer chips made of carbon nanotubes will be able to power systems of the future sooner than the industry expected”.

IBM has previously shown that carbon nanotube transistors can operate as excellent switches at channel dimensions of less than ten nanometers – the equivalent to 10,000 times thinner than a strand of human hair and less than half the size of today’s leading silicon technology.

Carbon nanotube chips have many benefits over traditional silicon. The researchers built a high-performance SWNT transistor with a sub-10-nanometer contact length, by reacting molybdenum films with semiconducting carbon nanotubes. Inside a chip, contacts are the valves that control the flow of electrons from metal into the channels of a semiconductor. Better transistors can offer higher speed while consume less power. Each nanotube carries only about 15 microamps, but IBM plans to solve that problem by just using as many nanotube channels in parallel as required for the type of drive a transistor needs for a particular location in a design. The recent work achieves that. However, as metal electrical contacts decrease in size, the associated resistance increases to impractical values.

Cross-sectional transmission electron microscope (TEM) image showing the fabricated nanotube transistor with an end-bonded contact. “Although the carrier injection area is limited to a ~2nm no barrier was observed for hole transport and resistance remained low”.

With chips made from carbon nanotubes-consisting of single atomic sheets of carbon in rolled-up tubes-high-performance computers may well be capable of analyzing big data faster, and they could also boost the battery life and power of mobile and connected devices.

In an interview with eWEEK, Shu-Jen Han, manager of the Nanoscale Science & Technology Group at IBM Research, said IBM’s breakthrough overcomes a major hurdle that silicon and any semiconductor transistor technologies face when scaling down. It’s now clear they can make the transistors as small as necessary, he says, and this is a big step toward the company’s goal of having carbon nanotube technology ready by 2020 (see “IBM: Commercial Nanotube Transistors Are Coming Soon”).

Besides helping to extend Moore’s law, Han foresees many other interesting applications for carbon nanotube transistors such as the base material for flexible electronics and transparent electronics.