A stepper is a highly accurate photolithography system that enables a pattern to be repeated on a wafer many times.

The traditional photolithography process creates a pattern on a substrate by shining light from a light source onto a photoresist that coats the surface of the substrate through a photomask and is followed by a development phase.

In a stepper, the substrate is placed on a moveable stage so that the pattern can be projected onto the resist-coated substrate, redirected, and the pattern repeated. This is very useful when trying to create many of the same component on a single wafer.