Electrons get faster

Feature size. Circuit speed and complexity. Throughput. The game hasn't changed. Electronics designers' constant efforts to pack more performance into every device, board, and system enormously complicates the process of developing and executing an effective test strategy.

And researchers at IBM are making sure we don't become complacent. At the Thomas J. Watson Research Center (Yorktown Heights, NY), company researchers have used existing manufacturing techniques to create the first logic circuit made from a single molecule.

This close-up view shows IBM’s five-stage CMOS ring oscillator. The inset shows the 2-nm-diameter nanotube itself. Courtesy of IBM.

Such resistance is primarily caused by plasmonic resonance, which hinders an electron's path when it becomes coupled with vibrations that occur in the lattice structure. The electrons traveling along the nanotube do not experience such resonance, suggesting that circuits built this way could prove much faster than anything available today, approaching terahertz speeds, according to the researchers. A single-molecule circuit will also likely eliminate the problem of crosstalk caused by electrons jumping from one pathway to another—a problem that increasingly plagues ever-smaller silicon designs.

The news comes as another reminder that test technologies always remain at least one step behind the products they are testing. Both designers and manufacturers must become more creative when building test and inspection strategies. They can no longer expect strategies of the past to have any relevance to newer developments.

Nevertheless, some test-equipment companies expect to take these new challenges in stride. Alan Wadsworth, marketing and communications manager of the Hachioji Semiconductor Test Division of Agilent Technologies, noted, "Since carbon nanotube FETs appear to conduct current via ballistic transport, circuits constructed from them will likely produce much higher current densities than we see in conventional MOSFET devices. From a parametric test perspective, this might require new reliability test routines and, potentially, hardware with increased current-sourcing capacity. However, I feel that the ability to test such devices is well within our current knowledge and equipment capabilities."