Silicon-germanium

SiGe (/ˈsɪɡiː/ or /ˈsaɪdʒiː/), or silicon-germanium, is a general term for the alloy Si1−xGex which consists of any molar ratio of silicon and germanium. It is commonly used as a semiconductor material in integrated circuits (ICs) for heterojunction bipolar transistors or as a strain-inducing layer for CMOS transistors. IBM introduced the technology into mainstream manufacturing in 1989.[1] This relatively new technology offers opportunities in mixed-signal circuit and analog circuit IC design and manufacture.

Production

The use of silicon-germanium as a semiconductor was championed by Bernie Meyerson.[2] SiGe is manufactured on silicon wafers using conventional silicon processing toolsets. SiGe processes achieve costs similar to those of silicon CMOS manufacturing and are lower than those of other heterojunction technologies such as gallium arsenide. Recently, organogermanium precursors (e.g. isobutylgermane, alkylgermanium trichlorides, and dimethylaminogermanium trichloride) have been examined as less hazardous liquid alternatives to germane for MOVPE deposition of Ge-containing films such as high purity Ge, SiGe, and strained silicon.[3][4]

SiGe foundry services are offered by several semiconductor technology companies. AMD disclosed a joint development with IBM for a SiGe stressed-silicon technology,[5] targeting the 65-nm process. TSMC also sells SiGe manufacturing capacity.

SiGe transistors

SiGe allows CMOS logic to be integrated with heterojunction bipolar transistors, making it suitable for mixed-signal circuits.[6] Heterojunction bipolar transistors have higher forward gain and lower reverse gain than traditional homojunction bipolar transistors. This translates into better low current and high frequency performance. Being a heterojunction technology with an adjustable band gap, the SiGe offers the opportunity for more flexible band gap tuning than silicon-only technology.

Silicon Germanium-on-insulator (SGOI) is a technology analogous to the Silicon-On-Insulator (SOI) technology currently employed in computer chips. SGOI increases the speed of the transistors inside microchips by straining the crystal lattice under the MOS transistor gate, resulting in improved electron mobility and higher drive currents. SiGe MOSFETs can also provide lower junction leakage due to the lower band gap value of SiGe.

Thermoelectric application

A silicon germanium thermoelectric device, MHW-RTG3, was used in the Voyager 1 and 2 spacecrafts.[7]

See also

References

  1. ↑ Ouellette, Jennifer (June/July 2002). "Silicon–Germanium Gives Semiconductors the Edge", The Industrial Physicist.
  2. ↑ B.S. Meyerson (March 1994). "Hi Speed Silicon Germanium Electronics". Scientific American, March 1994, vol. 270.iii pp. 42-47.
  3. ↑ E. Woelk, D. V. Shenai-Khatkhate, R. L. DiCarlo, Jr., A. Amamchyan, M. B. Power, B. Lamare, G. Beaudoin, I. Sagnes (2006). "Novel Organogermanium MOVPE Precursors". Journal of Crystal Growth 287 (2): 684–687. Bibcode:2006JCrGr.287..684W. doi:10.1016/j.jcrysgro.2005.10.094.
  4. ↑ Deo V. Shenai, Ronald L. DiCarlo, Michael B. Power, Artashes Amamchyan, Randall J. Goyette, Egbert Woelk (2007). "Safer alternative liquid germanium precursors for relaxed graded SiGe layers and strained silicon by MOVPE". Journal of Crystal Growth 298: 172–175. Bibcode:2007JCrGr.298..172S. doi:10.1016/j.jcrysgro.2006.10.194.
  5. ↑ AMD And IBM Unveil New, Higher Performance, More Power Efficient 65nm Process Technologies At Gathering Of Industry’s Top R&D Firms retrieved at March 16, 2007
  6. ↑ Cressler, J. D.; Niu, G. (2003). Silicon-Germanium Heterojunction Bipolar Transistors. Artech House. p. 13.
  7. ↑

Further reading

External links