New Speed Records for Transistors, ICs

The claim to the world's fastest silicon transistor was again taken by IBM (Hopewell Junction, N.Y.) with its silicon germanium heterojunction bipolar transistor (HBT) technology. With speeds of 350 GHz, the new transistor is 65% faster than previously reported silicon-based transistors. IBM anticipates that the new transistor will lead to communications chips with speeds of >150 GHz in about two years. The transistor is also expected to result in substantially lower power consumption and lower cost for communications systems and other electronic products.

IBM will present details of the technology in a paper, titled "SiGe HBTs with Cut-off Frequency Near 300 GHz," at this month's International Electron Devices Meeting (IEDM) in San Francisco.

"The industry recognizes the importance of SiGe technology, and everyone is racing to add it to their arsenal," said Bernard Meyerson, IBM fellow and chief technologist of IBM's Technology Group. "SiGe is imperative for true system-on-chip designs that pull together standard logic circuitry and higher-speed wireless communications circuitry. And while others are introducing their first versions, this is IBM's fifth generation of SiGe technology."

IBM’s SiGe HBT has a cut-off frequency of 350 GHz, making it the world’s fastest silicon transistor. Details will be presented at this month’s IEDM. (Source: IBM)

IBM's SiGe chips are built on existing manufacturing lines, allowing the technology to be introduced rapidly and at minimal cost. This has expanded the use of SiGe technology for extending function and battery life in cellular phones and other wireless communications products. IBM manufactures SiGe chips at its Burlington, Vt., facility.

In the "2002 McClean Report," published by research firm IC Insights , the firm estimates that SiGe sales totaled $320M in 2001 and are projected to grow to ~$2.7B by 2006. The report estimates that IBM SiGe activity accounted for >80% of total 2001 SiGe business.

In other work to be reported at IEDM, researchers from NTT Corp. (Tokyo) claim to have built the fastest logic function ever demonstrated on a transistor-based IC — a multiplexer/demultiplexer for fiber-optic communications. This is significant because light waves carry signals through optical fiber, but ICs at either end of the fiber must be used to encode and decode the information. Although such ICs are among the fastest transistor-based ICs, they limit the performance of optical fiber networks because they can't operate at anywhere near the speed of light, and the hunt is on to find ways to make them faster.

NTT fabricated two ICs containing 0.1 µm gate length high-electron-mobility transistors (HEMTs) made from an alloy of InAlAs/InGaAs/InP. One chip was the multiplexer/demultiplexer, the other was a test chip to confirm whether the first chip's logic operation was error-free. Researchers designed the mux/demux IC to eliminate the need for delay-causing output buffers. They demonstrated that the transistors had a maximum switching frequency of 350 GHz, fast enough to enable the "selector" core logic on the mux/demux IC to operate at a record speed of 100 Gb/sec. Previously, such ICs have been shown to operate only at 80 Gb/sec. A previous 90 Gb/sec record for logic operation was only seen as a waveform measurement on an oscilloscope.

In other record-breaking news, a Ph.D. student Daniel Kehrer, only 26 years old, established a new speed record in data transmission with an experimental CMOS circuit. He mastered this challenge at the corporate research center of Infineon Technologies (Munich). At 40 Gb/sec, he nearly doubled the all-time high of 25 Gb/sec that had been achieved in February, also at Infineon. In addition to Kehrer, the High Frequency Research department currently employs five other Ph.D. students. The team cooperates closely with the Technical Universities of Vienna and Cottbus as well as with the University of Bochum.

For additional information on wafer processing, go to www.semiconductor.net/wafer.