Semiconductor fabrication plant

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Photo of the interior of a clean room of a 300mm fab run by TSMC

In the microelectronics industry, a semiconductor fabrication plant, also called a fab or a foundry, is a factory where integrated circuits (ICs) are manufactured.^[1]

The cleanroom is where all fabrication takes place and contains the machinery for integrated circuit production such as steppers and/or scanners for photolithography, etching, cleaning, and doping. All these devices are extremely precise and thus extremely expensive.

Prices for pieces of equipment for the processing of 300 mm wafers range to upwards of $4,000,000 each with a few pieces of equipment reaching as high as $340,000,000 (e.g. EUV scanners). A typical fab will have several hundred equipment items. Semiconductor fabrication requires many expensive devices. Estimates put the cost of building a new fab at over one billion U.S. dollars with values as high as $3–4 billion not being uncommon. For example, TSMC invested $9.3 billion in its Fab15 in Taiwan.^[2] The same company estimations suggest that their future fab might cost $20 billion.^[3]

A foundry model emerged in the 1990s: Companies owning fabs that produced their own designs were known as integrated device manufacturers (IDMs). Companies that outsourced manufacturing of their designs were termed fabless semiconductor companies. Those foundries which did not create their own designs were called pure-play semiconductor foundries.^[4]

In the cleanroom, the environment is controlled to eliminate all dust, since even a single speck can ruin a microcircuit, which has nanoscale features much smaller than dust particles. The clean room must also be damped against vibration to enable nanometer-scale alignment of photolithography machines and must be kept within narrow bands of temperature and humidity. Vibration control may be achieved by using deep piles in the cleanroom's foundation that anchor the cleanroom to the bedrock, careful selection of the construction site, and/or using vibration dampers. Controlling temperature and humidity is critical for minimizing static electricity. Corona discharge sources can also be used to reduce static electricity.

Often, a fab will be constructed in the following manner (from top to bottom): the roof, which may contain air handling equipment that draws, purifies and cools outside air, an air plenum for distributing the air to several floor-mounted fan filter units, which are also part of the cleanroom's ceiling, the cleanroom itself, which may or may not have more than one story, ^[5] a return air plenum, the clean subfab that may contain support equipment for the machines in the cleanroom such as chemical delivery, purification, recycling and destruction systems, and the ground floor, that may contain electrical equipment. Fabs also often have some office space.