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Silicon on insulator
Silicon on insulator technology (SOI) refers to the use of a layered silicon-insulator-silicon substrate in place of conventional silicon substrates in semiconductor manufacturing, especially microelectronics, to reduce parasitic device capacitance and thereby improve performance. SOI-based devices differ from conventional silicon-built devices in that the silicon junction is above an electrical insulator, typically silicon dioxide or (less commonly) sapphire. The choice of insulator depends largely on intended application, with sapphire being used for radiation-sensitive applications and silicon oxide preferred for improved performance and diminished short channel effects in microelectronics devices . The precise thickness of the insulating layer and topmost silicon layer also vary widely with application. The first implementation of SOI was announced by IBM in August 1998.
Additional recommended knowledge
The implementation of SOI technology is one of several manufacturing strategies employed to allow the continued miniaturization of microlectronic devices, colloquially referred to as extending Moore's Law. Reported benefits of SOI technology relative to conventional silicon (bulk CMOS) processing include:
From a manufacturing perspective, SOI substrates are compatible with most conventional fab processes. In general, an SOI-based process may be implemented without special equipment or significant retooling of an existing factory. Among challenges unique to SOI are novel metrology requirements to account for the buried oxide layer and concerns about differential stress in the topmost silicon layer. The primary barrier to SOI implementation is the drastic increase in substrate cost, which contributes an estimated 10 - 15% increase to total manufacturing costs.
Manufacture of SOI wafers
SiO2-based SOI wafers can be produced by several methods:
An exhaustive review of these various manufacturing processes may be found in reference 
Use in the microelectronics industry
Examples of microprocessors built on SOI technology include AMD's 130 nm, 90 nm and 65 nm single, dual and quad core processors since 2001.  Freescale adopted SOI in their PowerPC 7455 CPU in late 2001, currently Freescale is shipping SOI products in 180nm, 130nm, 90nm and 65nm lines. IBM began to use SOI in PowerPC G4 7455 chips since late 2000.  The 90 nm PowerPC-based processors used in the Xbox 360, PlayStation 3 and Wii use SOI technology as well. Competitive offerings from Intel, however, such as the 65 nm Core 2 and Core 2 Duo microprocessors, are built using conventional bulk CMOS technology. Intel's new 45 nm process will continue to use conventional technology. However, Intel made a claim of single-chip silicon laser based on SOI. 
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Silicon_on_insulator". A list of authors is available in Wikipedia.