Two procedures are principally possible to manufacture e.g. conducting paths:
1. Etching technique: A thin metal film (e.g. aluminium) is deposited on a wafer (evaporation or sputtering), then resist structures are applied by photolithography and the metal is subsequently removed by etching. Those parts of the metal film which are covered by resist structures will remain during this procedure. A removal of resist structures will then uncover the conducting paths.
2. Lift-off procedure: In a first step, resist structures are generated on the wafer, followed by evaporation of a thin metal layer. After removing the resist mask, only the metal directly covering the wafer surface will remain while metal deposited on resist structures is washed away with the resist (lifted).
Overview General Process