a silicon-based technology that is compatible with
low-cost IC manufacturing – while still providing
these extreme levels of performance – allows us to
envision integrating these devices into systems that
would be affordable for emerging commercial markets
as well as defense applications," Cressler said.
The next step in this research will be to understand
the physics behind the silicon-germanium devices,
which display some unusual properties at these extremely
"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," said Cressler,
who heads the world's largest university-based silicon-germanium
research team at Georgia Tech. "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."
SiGe is a process technology in which the electrical
properties of silicon, the material underlying virtually
all modern microchips, is augmented with germanium
to make chips operate more efficiently. SiGe boosts
performance and reduces power consumption in chips
that go into cellular phones and other advanced communication
Silicon-germanium technology has been of great interest
to the electronics industry because it allows substantial
transistor performance improvements to be achieved
while using fabrication techniques compatible with
standard high-volume silicon-based manufacturing
processes. By introducing germanium into silicon
wafers at the atomic scale, engineers can boost performance
while retaining the many advantages of silicon.
IBM first announced its SiGe technology in 1989,
and later introduced SiGe into the industry's first
standard, high-volume SiGe chips in October 1998.
Since that time, the company has shipped hundreds
of millions of SiGe chips.
A laboratory and specialized test equipment used
in the research are located in the Georgia Electronic
Design Center (GEDC) at Georgia Tech.
"We are happy to see that the GEDC's continuing
support of research in high-speed mixed-signal technologies
and other device research is leading to more cost-effective
solutions for commercial applications," said Joy
Laskar, who is director of the GEDC and also the
Joseph M. Pettit Professor Chair in Electronics in
Georgia Tech's School of Electrical and Computer
Beyond Cressler, the research team included Georgia
Tech Ph.D. students Ramkumar Krithivasan and Yuan
Lu; Jae-Sun Rieh of Korea University in Seoul, South
Korea (formerly with IBM); and Marwan Khater, David
Ahlgren and Greg Freeman of IBM Microelectronics
in East Fishkill, N.Y.
"This new speed record provides encouragement to
keep pushing forward on silicon-germanium devices," Cressler
said. "There is a lot more fruit available from silicon-germanium
technology if we invest the effort to get there."
Contact: John Toon
Georgia Institute of Technology Research