Silicon wafer with silicon chips, 1984.

Silicon wafer, etched with multiple chips (integrated circuits), with round plastic case, American, 1984

A silicon wafer - an example of wafer-scale integration. Silicon chips are made by growing highly pure tubular silicon crystals, which are then sliced into thin wafers or circular discs. Many individual, identical chips are made simultaneously on each wafer in a series of optical and chemical processes, which involve introducing specific impurities into defined areas of each chip, forming semiconductor devices. The devices are connected electrically by deposits of aluminium, and the wafer is then broken into separate chips, which are individually encapsulated. The different varieties of chips which can be made control all of the operational processes and functions of a computer.