Logo: University of Southern California

CMOS: No Longer the Only Electronics Game In Town?

Computer chips are a $272 billion/year business - might nanowafers someday compete?
Eric Mankin
March 24, 2009 —

Scientists at the University of Southern California have demonstrated a process they say allows manufacturing of carbon nanotube wafers that can perform all the functions of silicon chips, at a potentially competitive cost.

Anatomy of a nanotube wafer, showing how standard circuit designs are realized using nanotubes rather than CMOS
The method created by a team led Professor Chongwu Zhou at the USC Viterbi School of Engineering's Ming Hsieh Department of Electrical Engineering  is described and illustrated in a recent paper in the journal Nano Letters (Nano Letters, 9, 189-197(2009)

Nanotubes, rolled up cylinders of pure carbon one atom thick with diameters around 1 nanometer (one billionth of one meter) had striking electronic properties. Theorists have long speculated that they might replace Complementary Metal Oxide Semiconductor  (CMOS) circuits to create, smaller, and more powerful and more versatile computers and portable electronic devices.

(Sales of CMOS-based chips in 2007 amounted to some $272 Billion in 2007, according to ComputerWorld.)

But the practical task of assembling the tiny, delicate threads into functional circuits on CD-sized wafers has daunting. And it is this task which Zhou says his team has made major progress in solving.

The work described in the article, “CMOS-Analogous Wafer-Scale Nanotube-on-Insulator Approach for Submicrometer Devices and Integrated Circuits Using Aligned Nanotubes” largely solves these problems, the researchers say. Along with Professor Zhou, the group includes graduate students Koungmin Ryu, Alexander Badmaev, and Chuan Wang.

"We solved major challenges such as the synthesis of massive aligned carbon nanotube over
Zhou 2
Nanoteam with wafer: from left Koungmin Ryu, Chongwu Zhou, Alexander Badmaev, and Chuan Wan.
CD-sized 4 inch quartz and sapphire substrates. In addition, we have developed a method to transfer carbon nanotubes from one substrate to another using thermal releasing tape, which can pick up carbon nanotubes and then release them onto whatever substrates at very low temperature,” says Zhou.

Other challenges the group solved include chemical doping of the nanotubes and defect-tolerant design of logic circuits. Using the technology, the group was able to demonstrate prototypes of integrated nanotube circuits, which can work as building blocks for integrated chips such as CPU or digital signal processor for computers and portable devices.

In a separate publication, Zhou's group also recently announced the creation of another key electronics component, supercapacitors, using nanotube technology.

Two Stanford research groups, led by Subhasish Mitra  and  H.-S. Philip Wong, also contributed to this work.

The Focus Center Research Program (FCRP FENA) and the National Science Foundation supported the research.