Electronic Design

Silicon-Germanium Technology Is Ready For Prime Time

Silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) have come a long way. Only a few years ago, there was a lot of skepticism about the commercial viability of implanting silicon with germanium, and then deriving transistors from this esoteric process. Today, many of those hurdles have been overcome and production issues alleviated, as well as the process refined and simplified. The result is faster bipolars delivering leading-edge solutions for RF circuits, including power amplifiers for mobile phones. In addition, this has allowed the merger of SiGe HBTs with mainstream CMOS technology to push biCMOS performance to new heights, accomplishing the integration of RF and analog/digital on the same die.

Consequently, strong proponents like IBM Microelectronics and Temic Semiconductors (a wholly owned subsidiary of Atmel Corp.) are in volume production. In fact, IBM is now in volume production of its third-generation SiGe technology, which includes 0.4- and 0.25-µm biCMOS. It plans to further boost the HBT performance and implement copper interconnects in 0.18-µm SiGe biCMOS by year's end. Interestingly, over a dozen semiconductor suppliers and systems houses are taking advantage of this progress by accessing IBM's SiGe foundry service via licensing deals.

This scenario has attracted many more players. Some include Conexant Systems Inc., Infineon Technologies, Maxim Integrated Products, Motorola Inc., Philips Semiconductor, and STMicroelectronics. Several of these newcomers are ramping up their production facilities and releasing parts based on their proprietary SiGe schemes. For instance, Motorola has successfully merged the SiGe:carbon process module, developed in cooperation with Frankfurt, Germany's High Performance Microelectronics, into mainstream RF-biCMOS technology. Plus, the company intends to sample low-noise amplifiers and other high-performance multiband, multimode RF ICs using the SiGe:C-based biCMOS later in the year, with production slated for early 2001. Also in this manufacturing fray is Conexant Systems, which has begun manufacturing new SiGe-based communications chips for low-power wireless and high-speed networking applications.

Furthermore, after demonstrating the viability of fabricating SiGe HBTs last year, STMicroelectronics is gearing up this year for production. Using its home-grown process, Maxim is expanding its product portfolio of SiGe devices to address the RF needs of its customers serving the wireless-communications space.

As SiGe pushes silicon deeper into the RF domain, the technology is being extended into a broad range of commercial and consumer applications. New performance standards also are being set by developers and adopters of SiGe-based solutions. Equally fast instrumentation is needed to test these chips and the systems in which they are implemented. Therefore, encouraged by the progress, Tektronix recently adopted SiGe as an alternative to expensive GaAs in the design of a 4-GHz bandwidth digital oscilloscope to keep pace with the higher data rates encountered in next-generation designs. Plus, Applied Micro Circuits Corp. unveiled an unprecedented 34- by 34-differential crosspoint switch with over 100-Gbit/s switching capacity.

In short, SiGe technology is poised for growth, as it spawns many new solutions for a new wave of products. But, ultimately, its growth will be influenced by its ability to scale smoothly with CMOS, as pure silicon enters the nanometer arena and achieves flexibility to add IP, memories, and cores for system-level integration.

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