The SiGe circuit--a ring oscillator operating at speeds over 110 GHz and processing electrical signals at 4.3 trillionths of a second--proves that silicon-based technologies will continue to outperform other compound semiconductors, such as gallium arsenide (GaAs) or indium phosphide (InP), said Bernard Meyerson, vice president of IBM Communications Research and Development Center.

During a speech at the 2002 Compound Semiconductor Outlook Conference today in San Mateo, Meyerson will describe the SiGe ring oscillator, which he said has a delay time of 4.3 picoseconds vs. 4.6 ps in recently disclosed "fastest" InP-based ring oscillator circuits.

"That 0.3-ps advantage is substantial, but more critically is that when the circuit is operating at lower power, it still has a speed advantage and a factor of 300-to-500% lower power consumption," Meyerson told SBN prior to his speech today.

"Not only did we come up with a SiGe technology that runs at tremendous speed and 30-to-40% faster than the world's prior 'fastest' example, but more importantly you can slow it down to run at the same speed with tremendous power savings," he added.

IBM said the first chips fabricated with the SiGe 8HP technology will be introduced later this year. The silicon-germanium process is IBM's fourth generation SiGe technology. IBM said it is now working with "early access customers"--including Sierra Monolithics Inc. of Redondo Beach, Calif.--to develop the first wired communications applications for SiGe 8HP.

Last summer, IBM Microelectronics disclosed development of the SiGe 8HP process by announcing it had created the world's fastest transistor that ran at speeds of 210 GHz while drawing only a milliamp of electrical current (see June 25 story). The new ring oscillator demonstrates the performance of SiGe 8HP in a functioning circuit block, which Meyerson said is a "real-world" indication of the actual benefits of a process technology vs. transistor measurements that are often debated among competitors.

"A ring oscillator is the 'golden standard circuit' used to demonstrate performance," said Meyerson, an IBM fellow who is a long-time advocate of silicon-germanium technology vs. GaAs and other compound semiconductors. "An oscillator delay is an actual delay measurement, period. You have a current, power, and a delay measurement," he said, suggesting that many high-speed transistor measurements have been more rhetorical than real.

In particular, Meyerson has taken issue with the use of Fmax (maximum frequencies) in what he calls a war of specsmanship in all high-speed transistor technologies. IBM has been critical of Conexant Systems Inc.'s recent claims of developing the world's fastest SiGe process for 80-gigabit-per-second devices (see Dec. 4 story).

Meyerson complained that Conexant used a loosely defined "unilateral maximum available gain" technique to measure Fmax, which can inflate the number compared to more conservative approaches, he said. But even using the same measurement method, IBM claims its SiGe 8HP transistors are 100-GHz faster than Conexant's specs, which were reported at the International Electron Devices Meeting (IEDM) in December.

In going up against recently announced specs for InP and GaAs devices, Meyerson said the new ring oscillator shows there is no contest in the future between silicon-based SiGe technologies and the other compounds.

"People have badly underestimated the extendibility of silicon," he declared.

Even Meyerson said he was surprised with the performance of the SiGe 8HP-based ring oscillator. "I was astounded that it outran the fastest circuit ever built in any technology--silicon, InP, or GaAs--it doesn't matter," he told . "That raises an interesting question about what is the 'technology of the future.'"

IBM's SiGe HP8 has a number of enhancements over the company's previous process generation, including tighter transistor layouts, reduced feature sizes, and band-gap engineering, which is a technique to grade the germanium atoms across the core of the bipolar device. "By grading the germanium content--which we have been doing for years internally and first demonstrated in 1989--we are able to accurately control the chemical composition on the order of a hundred atoms in a layer," Meyerson explained.

The band-gap engineering process step alters the physics of the transistor's transport mechanism. "We made a variety of improvements which to some extent shrinks the transistors but also changes their chemical and physical structures," Meyerson explained.

"To do that accurately is no small feat, but to do it in manufacturing is a major achievement," he added.

Separately today, IBM announced two tailored versions of an existing 0.5-micron SiGe BiCMOS process technology for wireless ICs. The two new SiGe foundry processes are the 5DM (dual-metal) technology, which is optimized for integration of passive elements, and the 5PA derivative, which is tuned for power amplifiers (see today's story).

--J. Robert Lineback