IBM aims for transistor speed crown

Paul Boughton

IBM is laying claim to the first silicon-based transistor to operate at over 500GHz, although it is not the first above that speed and has to be cooled to temperatures close to absolute zero.

IBM has been working with the Georgia Institute of Technology to reach this frequency by cooling a silicon germanium transistor to 4.5 Kelvin (-268.6 degC). Computer simulations suggest that the SiGe technology could ultimately support speeds near 1TeraHertz (1,000 GHz) even at room temperature.

Although this seems rather arcane, the chips used in the research are from a prototype fourth-generation SiGe technology fabricated by IBM on a 200mm wafer and run at 350GHz at room temperature

“For the first time, Georgia Tech and IBM have demonstrated that speeds of half a trillion cycles per second can be achieved in a commercial silicon-based technology, using large wafers and silicon-compatible low-cost manufacturing techniques,” said John Cressler, Byers Professor in Georgia Tech's School of Electrical and Computer Engineering. “This work redefines the upper bounds of what is possible using silicon-germanium nanotechnology techniques.”

“We observe effects in these devices at cryogenic temperatures which potentially make them faster than simple theory would suggest, and may allow us to ultimately make the devices even faster,” he said. “Understanding the basic physics of these advanced transistors arms us with knowledge that could make the next generation of silicon-based integrated circuits even better.”

However, this is not the fastest transistor, and SiGe is not mainstream process technology that CMOS is. Back in November 2003, the University of Illinois demonstrated a transistor running at 509GHz built in an exotic combination of indium phosphide and indium gallium arsenide as part of a project funded by the US DARPA military research programme.