Exposure
scale: wafer level (~300mm / 12 inch)
The photo resist finish is exposed to ultra violet (UV) light. The chemical reaction triggered by that process step is similar to what happens to film material in a film camera the moment you press the shutter button. The photo resist finish that’s exposed to UV light will become soluble. The exposure is done using masks that act like stencils in this process step. When used with UV light masks create the various circuit patterns on each layer of the microprocessor. A lens (middle) reduces the mask’s image. So what gets printed on the wafer is typically four times smaller linearly than the mask’s pattern.