Silicon Wafer Doping
Dopant Activation is the process of obtaining the desired electronic contribution from impurity species in a semiconductor host.[1] The term is often restricted to the application of thermal energy following the ion implantation of dopants. In the most common industrial example, rapid thermal processing is applied to silicon following the ion implantation of dopants such as phosphorus, arsenic and boron.
Doping during crystal growth Some dopants are added as the (usually silicon) boule is grown by Czochralski method, giving each wafer an almost uniform initial doping.[8]
Alternately, synthesis of semiconductor devices may involve the use of vapor-phase epitaxy. In vapor-phase epitaxy, a gas containing the dopant precursor can be introduced into the reactor. For example, in the case of n-type gas doping of gallium arsenide, hydrogen sulfide is added, and sulfur is incorporated into the structure.[9] This process is characterized by a constant concentration of sulfur on the surface.[10] In the case of semiconductors in general, only a very thin layer of the wafer needs to be doped in order to obtain the desired electronic properties.[11]
Post-growth doping To define circuit elements, selected areas — typically controlled by photolithography[12] — are further doped by such processes as diffusion[13] and ion implantation, the latter method being more popular in large production runs because of increased controllability.
https://en.wikipedia.org/wiki/Doping_(semiconductor)Ion Implantation
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