The silicon-germanium HMOS II consortium

EPSRC is releasing £4.3M to further support and extend a UK University Consortium which is carrying out research aimed at a SiGe MOS technology.

During the past twelve months SiGe has reached the status of a mainstream technology – but in the form of the base region in a Heterojunction Bipolar Transistor (HBT). This allows very significant performance enhancements in an otherwise Si technology, enabling silicon to access huge new markets in wireless and broadband, (e.g. optical communications) applications.

However, an even greater impact is predicted when SiGe is used in, or alongside, the dominant and versatile MOS based microelectronics technology – CMOS. This is especially the case as the system-on-a-chip era approaches. When incorporated into Si MOSFET devices – most likely via an epitaxy process, enhancements of at least the magic “factor of 2” in crucial performance parameters like upper frequency (f_T, f_max), noise (high frequency and flicker) and power consumption can be obtained. This would ultimately revolutionise Si technology, with SiGe being found in all leading-edge components where speed and/or power dissipation are market drivers. There is great merit in an all-silicon solution to mobile communication and internet access which could be facilitated by SiGe MOS.

However, the mechanisms by which SiGe brings performance enhancements to MOSFET devices are more subtle than those operating in the SiGe HBT – and these can be diminished by inappropriate processing. The trick is to combine new designs of the MOSFET vertical architecture which are resilient to/compatible with the prevailing process schedules – allowing SiGe MOS devices to be fully integratable, speeding up either the entire circuit or certain crucial parts such as mobile handset front ends.

The necessary concentration of research effort including design, material growth and process development, is contained within this UK University Consortium – with the Universities of Cambridge, Glasgow, Imperial College (London), Loughborough, Newcastle, Sheffield, Southampton, UMIST and Warwick involved. A strong applications-focus is helped by the involvement of Daimler-Chrysler (Ulm) (a world-leading centre in SiGe), Infineon (Munich) and Mitel Semiconductors (Plymouth) and the software house Avant! (San Francisco) is also working with them.