How does it work?

Photolithography, literally meaning light-stone-writing in Greek, is the process by which patterns on a semiconductor material can be defined using light. It is the means by which the small-scale features of integrated circuits are created.

A resist is applied to the surface using a spin-coating machine, this holding and spinning the thin film sample at high speed for 15-30 seconds. The resist is then gently heated in a convection oven and then a hotplate to evaporate to partially solidify.

A photomask containing the desired final pattern is placed upon or close to the the spun solid resist and carefully aligned with a mask-aligner.

A light projection system within the aligner is then used to expose the resist to UV light. During the exposure process, the resist undergoes a chemical reaction and causes the resist to decompose. After the developing process, a negative of the mask remains as a pattern of resist. After either further deposition of semiconductor layers or metal or etching down to selectively remove material, the resist can be removed. Commonly, photoresists are removed using acetone, trichloroethylene and phenol-based strippers.