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Carbon nanotube breakthrough could extend Moore's Law

Posted: 05 Oct 2015 ?? ?Print Version ?Bookmark and Share

Keywords:IBM? Moore's Law? CMOS? EUV? carbon nanotube?

Analyst Doherty was impressed by IBM's "welding" technique and thinks it will give IBM a competitive advantage over the competition. It works by coating the end of the nanotubes with molybdenum before their self-aligned placement as transistor channels. Then the 'welding' step is completed by heating the whole assembly to 850C thus melting the molybdenum and chemically transforming it into carbide, a conductor that makes an excellent angstrom-scale contacts.

IBM's on/off current switching ratio of 10,000

"This clever welding/carbide discovery seems to be the only silicon-processing favourable metal without oxidation problems and or Schottky barrier characteristics would add an undesirable step-voltage threshold. Rather IBM's method has an on/off current switching ratio of 10,000, which is great," Doherty said. "Others trying side connection schemes [to nanotubes] seem to vary in resistance and conductance over time, making them only lab curiosities. IBM's end-cap success paves the way for real nanotube structures that can make use of already proven silicon photolithography techniques.

Carbon nanotube schematics

Schematic showing a fabricated set of devices with different contact geometries on the same nanotube to verify that the contact size can shrink without reducing device performance. (Source: IBM Research, used with permission)

Today IBM is only able to produce p-type transistors using its revolutionary "welding" technique, but it claims the devices work better than FinFETs and their next step, already under way with light at the end of the tunnel, according to Han, is n-type devises so that CMOS nanotube transistors can be fabricated at the 3nm node by the time silicon FinFETs reach the 5nm node.

"IBM's internal goal is to be ready to come in at the 5nm node and become the best option for the 3nm node all the way down to the angstrom level," Hans indicated.

According to Doherty, IBM's achievement gives new hope to extending Moore's Law into the indefinite future, since no insurmountable scaling problems are seen for the nanotube 'welding' technique, which Doherty dubs IBM's "coaxial connection" technology.

"And succeeding with these coaxial end caps at 9nm gives courage and confidence to the industry to there being an alternative semiconductor path as silicon gets more and more inefficient as we push its limits under Moore's Law," Doherty added. "Also I have rarely seen a paper [IBM's Science paper] with so many attributions to other researchers. Their goal is production within a decade, but I am sure they want it faster than that if possible."

IBM's success is a part of its $3 billion research and development effort for post-silicon technologies, started in 2014, to pave the way to the computing needs of what IBM calls the coming "cognitive computing era."

- R. Colin Johnson
??EE Times

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