Silicon-on-Sapphire

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Cross section through a transistor in an integrated circuit on an SOS substrate

In semiconductor technology , silicon -on-sapphire (SOS, English: 'silicon on sapphire') refers toa special design for semiconductor components made of silicon on the insulating substrate made of sapphire .

SOS is part of the silicon-on-insulator family (SOI, "silicon on an insulator").

The integrated circuits (ICs) are manufactured in a heteroepitaxial process in which a thin layer of monocrystalline silicon is produced on a sapphire wafer . The sapphire wafers are cut from highly pure, artificially grown single crystal sapphire. The advantages of sapphire are its good electrical insulation , which prevents voltages scattered by ionizing radiation from affecting neighboring circuit elements, as well as its roughly matching lattice constant and also its high thermal conductivity.

SOS enables the manufacture of transistors and ICs with particularly high operating voltage or particularly high radiation resistance (for example for use in satellites in the area of ​​the Van Allen belt ) and are primarily used in aeronautical and military applications. The RCA1802 microprocessor is a well-known example of a semiconductor manufactured using the SOS process.

SOS was little used commercially, at least until 2006, because it is very difficult to make extremely small transistors. However, these are required for highly integrated components. The difficulty arises from dislocations that arise due to the disparity of the crystal lattice between the silicon and sapphire.

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