Electrical characteristics are thereby altered to create separate regions with excess negative or positive charges. Metallization is a type of deposition process. Here, many interconnections are formed on each of hundreds of integrated circuits being formed on every wafer. Metallization is also used for bond pads that interconnect a chip to other components on a printed wiring board. During ion implantation , dopants or other impurities are introduced into a wafer's surface to create silicon crystals that conduct electricity.
Masks expose a chemical coating called photoresist to ultraviolet light.
In turn, the photoresist hardens in desired patterns when it is developed. During the etching process , wafers are moved to a plasma reactor where electrically excited gases etch the surface into the pattern defined by the photolithography process. After etching, wafers are cleaned thoroughly. Toward final wafer fabrication , each wafer is subjected to testing to determine defective components. Silicon nitride, a protective coating, is applied.