Copper interconnections on CMOS could become a bottleneck as future chips get faster. One solution could be harnessing carbon nanotubes, which have much higher electron mobility. Until now, however, researchers have been unable to perfect a method for coaxing the nanoscale carbon tubes into the correct positions on chips. Now, one group thinks they have the answer. The world's first CMOS circuit using nanotubes as an interconnect was recently designed at Stanford University, in cooperation with Toshiba Corp. I t was fabricated by Taiwan Semiconductor Manufacturing Co. Ltd. (TSMC). The 256 ring oscillators on the 11,000- transistor chip ran at 1 GHz, rivaling the speed of other advanced CMOS chips (the iPhone's processor runs at 700 MHz).