The heart of any semiconductor manufacturing business is the "foundry," where the integrated circuit is formed on the wafer. The fabrication process, which takes place in an environmentally controlled clean room, involves a series of principle repetitive steps described below. Typically, it takes from 10-30 days to complete the fabrication process.

1. Thermal Oxidation
2. Patterning
3. Etching
4. Doping / Diffusion
5. Final Step

The thermal oxidation, masking, etching and doping steps are repeated many times until the last "front end" layer is completed (all active devices have been formed).

Following completion of the "front end," the individual devices are interconnected "backend" (like on a PC board) using a series of alternating metal depositions, dielectric films, with their respective patterning. Current semiconductor fabrication includes as many as 3 to 5 metal layers separated by dielectric layers (insulators).

After the last metal is patterned, a final insulating layer (passivation) is deposited to protect the circuit from damage and contamination. Openings are etched in this film to allow access to the top metal later by electrical probes and subsequent wire bonds.

An automatic, computer-driven test system checks for functionality of each chip on the wafer. Chips that do not pass the test are marked for automatic rejection. For simpler devices a mechanical probe is used.