IC
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History of Computers: The
manufacture of chips involves various steps according to the
type of chip being produced. Each step may be repeated many times. Deposition, or growing an insulating layer on the slice of silicon, is the first step. Its purpose is to install a layer on the wafer's silicon substrate that can be patterned using photolithography to form circuit elements. During diffusion, impurities are baked into the wafer in a diffusion furnace. 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. Wafers are then ready for the final processing step, multiprobe testing. Each integrated circuit in the wafer is electrically tested to determine whether or not a chip is ready for final assembly, bonding and packaging References: |
