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The commonest use of particle accelerators is in the ion implantation process, where dopant ions are implanted in the surface of a semiconductor wafer to produce electronic devices.

The technology is now decades old, and many implanters are in use around the world in wafer fabrication plants. The process is complementary to the various diffusion methods, and has advantages and disadvantages:

(1) Lack of edge effects means an implanted device can be made much smaller than a comparable diffused device.
(2) Dopant sources are much smaller and more controllable, negating the need for process exhaust cleaning.
(3) The low temperature of the target wafer means that compound semiconductors, such as gallium arsenide, can be processed without fear of the lighter element boiling away.
(4) Device features can only be implanted a few microns deep into the wafer, whereas diffusion can produce deep layers.
(5) Capital expenditure on implanters is much higher than diffusion furnaces.

The particle accelerator is used to increase the energy of ionised dopant source material to a level where it may be implanted at the required depth. Dopant species selection is usually by mass spectrometry, where powerful electromagnets bend the accelerated beam through a specified angle. Only the correct isotope has the mass to bend toward the target; the remaining contaminants spray harmlessly around the inside of the final scanning system.

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