Meet the New Silicon Speed Demon


The annual International Electron Devices Meeting (IEDM) is just around the corner, so expect a slew of announcements about new all-time records and semiconductor breakthroughs over the next few weeks. IEDM is traditionally the place where chipmakers and silicon engineers uncork major innovations that could affect all things electronic in coming years. This year's meeting will convene in San Francisco from Dec. 9 to 11.

IBM (IBM) got the ball rolling on Nov. 4 by proclaiming it would divulge details about the world's fastest silicon-based transistor at IEDM. This little speedster switches on and off at the blazing rate of 350 billion times a second, or 350 gigahertz (GHz). By the time IEDM rolls around, its new record might even jump to 400 GHz. But 350 GHz is plenty fast -- four times the speed of today's top commercial designs and 65% better than the previous laboratory record.

True, this isn't your garden-variety transistor. First off, it's made from a so-called compound semiconductor, a mixture of silicon and germanium that IBM has been developing for 15 years. Second, it's a bipolar transistor, intended for use in telecom systems and other circuits that process real-world analog signals, like music and voices, not the digital bits that flit around the logic and memory chips inside computers.

ALWAYS CONNECTED. Still, IBM sees huge potential for this technology -- as do other big-league chipmakers. The entire electronics industry is gearing up for the long-heralded era of the "system on a chip." Next year, the lines on cutting-edge chips will shrink to 90 nanometers (nm), or 0.09 micron. That's 1/1,000th the width of a human hair and 30% thinner than today's skimpiest 130-nm lines. By 2005, circuit lines will dwindle further, to 65 nm, with 45 nm due shortly after that.

These ultraslim lines will mean chips can be packed with all the transistors that most products need -- ergo, one chip per product (well, at first, maybe one microprocessor plus one memory chip). By mid-decade, Intel (INTC) figures virtually all microprocessors and memory chips could come with their own built-in radio circuits, bringing wireless connectivity to almost every electronics gizmo.

Except for one small problem: Digital and analog chips aren't made the same way. They haven't even used the same base material, traditionally. Plain old silicon is the standby for logic chips, of course, but it's not fast enough to handle a steady diet of high-speed analog signals. For analog chips, compound semiconductors such as gallium arsenide and indium phosphide are the typical choice. But these materials can't be processed in silicon-chip factories without chucking a lot of very expensive equipment.

MATERIAL GUY. For economically bridging the analog and digital worlds, silicon germanium (SiGe) heads the list of candidate materials. In fact, Bernard Meyerson, an IBM research fellow and chief technologist for IBM Microelectronics, declares unequivocally that "SiGe will be imperative" for tomorrow's system-on-a-chip designs. He believes it will replace everything else for combining digital and analog circuits. But he's a trifle biased: Meyerson has spearheaded IBM's SiGe research and development from its beginnings.

He also makes no apology for being so cocksure that his pet will be the system-on-a-chip workhorse. "We did the basic science, so we know its potential," Meyerson explains. "As early as 1990, we knew that a 35,000% improvement was possible in what was then supposed to be a mature, well-understood material. And we had SiGe roadmaps for all semiconductor structures," both digital and analog.

Back then, Meyerson muses, had he predicted that a silicon-based material would attain a speed of 350 GHz a decade later, "it would have caused peals of derisive laughter." Now, he boasts, the world's top-25 chipmakers have seen the silicon-germanium light. "They're all rushing to copy us." Chalk up one for science-based bullheadedness. By Otis Port in New York


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