Semiconductor test wafers

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A wafer is a thin slice of semiconductor material, such as a silicon crystal, used in the fabrication of integrated circuits and other microdevices. The wafer serves as the substrate for microelectronic devices built in and over the wafer and undergoes many microfabrication process steps such as doping or ion implantation, etching, deposition of various materials, and photolithographic patterning. Finally the individual microcircuits are separated (dicing) and packaged.
Wafers are formed of highly pure (*9.***9% purity),[1] nearly defect-free single crystalline material.[2] One process for forming crystalline wafers is known as Czochralski growth invented by the Polish chemist Jan Czochralski. In this process, a cylindrical ingot of high purity monocrystalline silicon is formed by pulling a seed crystal from a 'melt'.[3][4] Dopant impurity atoms such as boron or phosphorus can be added to the molten intrinsic silicon in precise amounts in order to dope the silicon, thus changing it into n-type or p-type extrinsic silicon.

The ingot is then sliced with a wafer saw (wire saw) and polished to form wafers.[5] The size of wafers for photovoltaics is **0–**0 mm square and the thickness is **0–**0 μm. In the future, **0 μm will be the standard.[6] Electronics use wafer sizes from **0–**0 mm diameter. (The largest wafer made has a diameter of **0 mm but is not in production yet.)