IBM and Georgia Tech Push Silicon's Speed Limit up to 500 GHz

Published: June 27, 2006

by Timothy Prickett Morgan

Researchers at IBM and the Georgia Institute of Technology have collaborated in an effort to see how far current silicon-based chip making techniques can be pushed to continue boosting performance of the transistors that make up electronic circuits.

Just about every report on IBM-Georgia Tech has said that the two were testing chips, and that they had frozen chips to nearly absolute zero and been able to crank the clock cycles on them to 500 GHz. That was almost correct. First, according to John Cressler, the researcher at Georgia Tech who was doing the work, the two were not testing chips, but rather transistor building blocks. And secondly, you can't freeze a chip, since it is already a solid, but you can cool the transistors being tested to -450 degrees Fahrenheit, which is precisely what the team did. To test the limits of silicon technology, IBM made the transistor circuits, doping them with germanium, and by cooling the chips, the two were able to get the transistors to switch at 500 GHz. This is about 200 times faster than the fastest server chips on the market. Without the helium cooling, IBM and Georgia Tech have been able to operate the simple circuits at around 350 GHz.

And no, IBM is not planning on adding liquid helium cooling to server processors some time in the future. Cressler explained that the cooling was only necessary to see how far the circuits could be pushed in terms of clock speed. The goal is to find the ultimate limits of silicon chip technology using current manufacturing techniques, and then apply that learning to create room temperature electronic circuits. The earliest applications of such knowledge will probably not be for processors, according to Cressler, but rather for high speed circuits used in wireline and wireless communications. Such circuits already crank faster than server processors, and are made using silicon doped with germanium. IBM announced its first silicon germanium processors in the labs in 1989, and went into production with special chips in 1998; the company has shipped hundreds of millions of processors using this technology since that time.