SiGe, or silicon-germanium, is the alloy of silicon and germanium. This semiconductor material is commonly used in the integrated circuit manufacturing industry, where it is employed for producing heterojunction bipolar transistors or as a strain-inducing layer for CMOS transistors. This relatively new technology offers interesting opportunities in mixed-signal circuit and analog circuit IC design and manufacture. Some of the key points of SiGe include:

• SiGe is manufactured on conventional silicon wafers and leverages conventional silicon processing toolsets. By leveraging established silicon process equipment, SiGe processes achieve costs that are similar to silicon CMOS manufacturing versus other more expensive heterojunction technologies such as gallium arsenide.

• SiGe allows state-of-the-art CMOS logic to be highly integrated with ultra high performance heterojunction bipolar transistors, making it optimal for mixed-signal circuits.

• Heterojunction bipolar transistors have significantly higher forward gain and lower reverse gain which translates into better low current and high frequency performance than typically available from homojunction or traditional bipolar transistors

• Being a heterojunction technology, the opportunity for band gap tuning exists which has normally been available only to compound semiconductors.

The major players in SiGe foundry services are IBM, STMicroelectronics, TSMC, Freescale (originally Motorola Semiconductor), Sony, Atmel, Chartered Semiconductor, Micrel and Jazz Semiconductor (originally Conexant). SiGe

Alloys | Integrated circuits | Semiconductor materials | Silicon compounds | Germanium compounds