Silicon on sapphire 747222 222086242 2008-06-27T14:18:50Z Moonriddengirl 4066002 Removing copyvio; material copied directly from http://www.ece.jhu.edu/Seminars/Culurciello%20Defense.htm DO NOT RESTORE. See talk '''Silicon on sapphire (SOS)''' is a hetero-epitaxial process for [[integrated circuit]] manufacturing that consists of a thin layer (typically thinner than 0.6 micrometres) of [[silicon]] grown on a [[sapphire]] (Al<sub>2</sub>O<sub>3</sub>) wafer. SOS is part of the [[Silicon on Insulator]] (SOI) family of [[CMOS]] technologies. SOS is primarily used in [[aerospace]] and [[military]] applications because of its inherent [[radiation hardened|resistance to radiation]]. Typically, high-purity artificially grown [[sapphire]] crystals are used. The silicon is usually deposited by the decomposition of silane gas (SiH4) on heated sapphire substrates. The advantage of sapphire is that it is an excellent [[Electrical insulation|electrical insulator]], preventing stray [[Current (electricity)|currents]] caused by radiation from spreading to nearby circuit elements. SOS has seen little commercial use to date because of difficulties in fabricating the very small [[transistor]]s used in modern high-density applications. This drawback is because the SOS process results in the formation of dislocations, twinning and stacking faults from [[crystal lattice]] disparities between the sapphire and silicon. Additionally, there is some aluminium, a p-type dopant, contamination from the substrate in the silicon closest to the interface. ==Silicon on Sapphire Circuits and Systems== [[Image:Patchdiesos.jpg|frame|right|A [[Silicon on Sapphire]] ''microchip designed by e-Lab [http://www.eng.yale.edu/elab/]'']] The advantages of the SOS technology allowed research groups as Yale e-Lab to fabricate a variety of SOS circuits and system that benefit from the technology and advance the state-of-the-art in: * analog-to-digital converters (a nano-Watts prototype was produced by Yale e-Lab)[http://pantheon.yale.edu/~ec337/pubs/ADCTCASII2006.pdf][http://pantheon.yale.edu/~ec337/pubs/2c1cisosadc.pdf] * monolithic digital isolation buffers [http://pantheon.yale.edu/~ec337/pubs/isoAICSP2006.pdf] * SOS-CMOS image sensor arrays (one of the first standard CMOS image sensor arrays capable of transducing light simultaneously from both sides of the die was produced by Yale e-Lab)[http://pantheon.yale.edu/~ec337/pubs/eletsSOSImgrRev1.pdf] * patch-clamp amplifiers [http://pantheon.yale.edu/~ec337/pubs/iscas06%20patchi06.pdf] * energy harvesting devices [http://pantheon.yale.edu/~ec337/pubs/harvestEL2006.pdf] * three-dimensional (3D) integration with no galvanic connections * charge pumps [http://pantheon.yale.edu/~ec337/pubs/el2005_isolationcp.pdf] * temperature sensors [http://pantheon.yale.edu/~ec337/pubs/harvestEL2006.pdf] == Substrate Analysis - SOS Structure == [[Image:TEM cross-section of epitaxially grown silicon and sapphire substrate.JPG|frame|right|TEM Cross-Section of epitaxially grown silicon and sapphire substrate taken by Semiconductor Insights'']] The application of epitaxial growth of silicon on sapphire substrates for fabricating MOS devices involves a silicon purification process that mitigates crystal defects which result from a mismatch between sapphire and silicon lattices. The Peregrine PE42612 SP4T switch is formed on an SOS substrate where the final thickness of silicon is approximately 95nm. Silicon is recessed in regions outside the polysilicon gate stack by poly oxidation and further recessed by the sidewall spacer formation process to a thickness of approximately 78nm. == Commercial SOS IC Production == Located in San Diego, California, Peregrine Semiconductor is a leader in SOS products. Its patented UltraCMOS process provides superior RF performance. Increasing market demand for SOS ICs has seen the company grow rapidly. == See also == * [[Silicon on Insulator]] * [[Radiation hardening]] * [[e-Lab]] * [[Semiconductor Insights]] [[Category:Thin film deposition]] [[Category:Semiconductor device fabrication]] [[de:Silicon on Sapphire]]