Fab (Fabrication plant)

Notes

Depreciation, not labour or materials, is the largest single line in leading-edge wafer cost, which is why utilisation is everything.

Overview

A fab, short for fabrication plant, is the factory where transistors and wiring are built onto wafers layer by layer, inside an ultra-clean, tightly controlled cleanroom. Its output is finished wafers, not packaged chips: cutting, packaging and final test usually happen elsewhere, often at an assembly and test company. Leading-edge fabs are among the most expensive factories built in any industry, costing tens of billions of dollars.

How it works

A fab is built around its cleanroom. Filtered air is pushed down through fan filter units in the ceiling, and temperature, humidity and vibration are held within narrow limits so that nanometre-scale patterns line up. Beneath the cleanroom a subfab holds the pumps, chemical and gas delivery, ultrapure water and exhaust treatment that the process tools need.

Each wafer goes through repeated loops of deposition, lithography, etch, ion implantation, cleaning and polishing, with measurements after critical steps. The first part of the flow builds the transistors (front end of line); the second builds the stack of metal wiring above them (back end of line). Wafers travel between tools in sealed carriers, often on overhead transport, and a manufacturing execution system tracks every lot.

Equipment is most of the cost: a fab holds hundreds of tools, and the most advanced lithography scanners cost hundreds of millions of dollars each. Because those costs are fixed, a fab must run close to full to pay for itself, which is the logic behind sharing capacity through the foundry model.

Examples

• A leading-edge logic fab running 300 mm wafers with EUV lithography to make processors and AI accelerators.
• A memory fab producing DRAM or 3D NAND, where a few product types run in very high volume.
• A 200 mm analogue and power fab on mature processes, often decades old but still fully loaded.
• A compound semiconductor fab processing gallium arsenide or silicon carbide on smaller wafers for radio or power devices.
• A university or research cleanroom used for prototypes and process research rather than volume production.

Why it matters

Fabs employ process, equipment, facilities, yield and automation engineers, and their decisions ripple outwards: the fab's process defines the design kit that chip designers use, and its capacity sets lead times for everyone downstream.

In the chip lifecycle, the fab sits between tapeout and assembly and test. New process technologies are developed in fabs years before products use them, and a fab keeps running mature processes long after the leading edge has moved on.

It matters most to: Fab Director, Fab Equipment Engineer, Fab Facilities and Ultrapure Utilities Engineer, Process Integration Engineer, Yield Enhancement Engineer

Common confusions

Not the same as foundry

A foundry is a business that makes chips for other companies; a fab is the building where wafers are processed. Foundries run fabs, but so do companies that make only their own chips, such as many memory makers. Fab vs foundry

Not the same as an assembly and test plant

Packaging and final test are separate operations, often in another country. Note also that "back end" means metal wiring inside a fab but assembly and test in the wider industry.

Related standards

• ISO 14644-1 (classification of cleanroom air cleanliness by particle concentration)
• SEMI S2 (environmental, health and safety guideline for semiconductor manufacturing equipment)
• SEMI E10 (equipment reliability, availability, maintainability and utilisation)

Sources

1. ISO 14644-1:2015 Cleanrooms and associated controlled environments, Part 1: Classification of air cleanliness by particle concentration (opens in a new tab), ISO, 2026-10-22
2. SEMI S2: Environmental, Health, and Safety Guideline for Semiconductor Manufacturing Equipment (opens in a new tab), SEMI, 2026-10-22
3. SEMI E10: Specification for Definition and Measurement of Equipment Reliability, Availability, and Maintainability (RAM) and Utilization (opens in a new tab), SEMI, 2026-10-22
4. Semiconductor fabrication plant (Wikipedia) (opens in a new tab), Wikimedia Foundation, 2026-10-22
5. Cleanroom (Wikipedia) (opens in a new tab), Wikimedia Foundation, 2026-10-22

Related terms

• Front-end
• WSPM
• Rock's Law
• Foundry

Where it appears on the Hub

Used on 504 pages of the Hub. In each group, the pages that mention it most come first.