Wafer (electronics)

A wafer, also called a slice or substrate, is a thin slice of semiconductor material, such as a crystalline silicon, used in electronics for the fabrication of integrated circuits and in photovoltaics for conventional, wafer-based solar cells. 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.

History

By 1960, silicon wafers were being manufactured in the U.S. by companies such as MEMC/SunEdison. In 1965, American engineers Eric O. Ernst, Donald J. Hurd, and Gerard Seeley, while working under IBM, filed Patent US3423629A for the first high-capacity epitaxial apparatus.

Formation

Wafers are formed of highly pure (99.9999999% purity), nearly defect-free single crystalline material. 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 mono crystalline semiconductor, such as silicon or germanium, called a boule, is formed by pulling a seed crystal from a 'melt'. Donor impurity atoms, such as boron or phosphorus in the case of silicon, can be added to the molten intrinsic material in precise amounts in order to dope the crystal, thus changing it into n-type or p-type extrinsic semiconductor.

Electronics

Electronics is the science of how to control electric energy, energy in which the electrons have a fundamental role. Electronics deals with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive electrical components and interconnection technologies. Commonly, electronic devices contain circuitry consisting primarily or exclusively of active semiconductors supplemented with passive elements; such a circuit is described as an electronic circuit.

The nonlinear behaviour of active components and their ability to control electron flows makes amplification of weak signals possible, and electronics is widely used in information processing, telecommunication, and signal processing. The ability of electronic devices to act as switches makes digital information processing possible. Interconnection technologies such as circuit boards, electronics packaging technology, and other varied forms of communication infrastructure complete circuit functionality and transform the mixed components into a regular working system.