Monday, March 27, 2006

"CHIPS: Single-molecule nanotube oscillator ripe for CMOS"

IBM Corp.'s T.J. Watson Research Center has crafted an experimental IC that uses a single-molecule nanotube as the common transistor channel for five CMOS-like inverters wired as a ring oscillator. The fully integrated device, which reportedly runs 400,000 times faster than the fastest nanotube-based circuits developed at other labs, could serve as a blueprint for integrating nanotube transistors into production CMOS chips. Experimental methods of adding nanotube-based transistors to standard CMOS circuits have been tried at IBM and elsewhere, but all have had to fall back on manual manipulations with an atomic-force microscope or have had to resort to exotic processing steps. But the new work demonstrates that fully integrated circuits are possible by growing nanotubes in place on a standard silicon substrate and then adding metallization layers using standard photolithographic techniques. It also demonstrates that standard CMOS circuitry can be crafted with the nanotube serving as the channel for both p-and n-type transistors. The work builds on an achievement declared in 2001, when IBM demonstrated the use of nanotubes to enable a transistor channel measuring 15 angstroms (1.5 nanometers)--over 40 times smaller than the tiniest features on today's state-of-the-art 65-nm silicon ICs. Using single-molecule nanotubes for each device on future ICs could simplify manufacturing and provide the kind of rigorous consistency needed to adapt commercial CMOS processes for use with carbon nanotube transistors