By John Dodge
March 7, 2002 | The potential for IBM’s new “double-gate” transistor technology ranges somewhere between “evolutionary and revolutionary” in the estimation of Markus Levy, senior analyst with the newsletter The Microprocessor Report.
“When you’re talking about getting down that small, it’s pretty tricky as far being able to lay it out and build it,” says Levy. Regardless, IBM has a solid track record of commercializing chip innovations, he says.
Still, it will be 2006 or later before the technology is put into commercial microprocessors, concedes Jeff Welser, IBM project manager for high performance CMOS technology. He estimates that once implemented, double-gate transistor technology could yield average performance improvements between 25 and 30 percent.
Theoretically, double-gate technology can carry twice the electrical current of today’s single gate transistors and operate twice as fast. However, the more significant advance may be reduced power consumption, which is always a prime concern in portable computers.
“We are continuing to run into more difficulties in scaling up performance and making things smaller. Chips get faster, but leak more current. Enter double gate where you have twice the ability to turn current on and off,” explains Melser. “Think of it this way. It’s like shutting off water by pinching a garden hose at both of the ends. You have twice the ability to shut off the water.”
When leakage is multiplied times many millions of transistor gates, power loss becomes more significant as chip complexity increases.
IBM has long known it could construct double-gate transistors, but in early December announced it developed and manufactured them using conventional CMOS process.
“It’s been around a while in the lab, but was not a structure anyone would consider manufacturing. Now it looks like a reasonable device and on par with what we can do in single gate devices,” says Melser.
According to IBM vice president of semiconductor development Bijan Davari, the breakthrough was made possible by a new chip making material know as Silicon on Insulator or SOI for short.
“SOI is changing the rules in semiconductors,” Davari said in a press statement. “Other than getting smaller, the basic transistor has largely gone unchanged for decades, but it has now been shrunk nearly to a point where it will cease to function. SOI allows us to change the basic design of the transistor, permitting further shrinkage and other improvements.”