This image shows a photolithographic stepper, which is used to put patterns on semiconductor wafers using a photographic process. The wafers are coated with a light-sensitive resist, and the patterns that define a chip are developed into the resist by shining light through a pattern mask, as shown.
Once the resist patterns are developed, the exposed patterns on the wafer can be etched, doped, or otherwise chemically modified to create thousands of transistors.
A chip manufacturer would use a stepper, like the one shown here, to step many hundreds of wafers per hour through this process using the same mask.
Photograph courtesy of the The Fullman Company