After cleaning, a photo resist coating is applied to the surface of the substrate using one of several methods. Photo resist is a light sensitive material in which the area that has been exposed to light either hardens or washes away when liquid developer is applied. Some photo resists are "positive", meaning that the areas exposed to light wash away. Other photo resists are "negative", meaning that the non-exposed area washes away. After application most photo resists are baked before exposure.

The coated substrate is placed into an exposure system where a pattern is photographically transferred, or exposed into the photo resist. One type of exposure tools are direct write laser systems such as e-beam pattern generators and laser pattern generators where graphical CAD data is converted and directly written into the photo resist using a small beam that sweeps across the surface. Flood exposure systems such as steppers, aligners and contact printers use a photomask to transfer the image to the photo resist on another substrate by shining light through the photomask.

A photomask is a glass substrate with the pattern etched into a thin coating of chrome on one surface. The glass substrate is usually soda lime, white crown, or quartz (fused silica), although other types of glass such as BK7 are used. The chrome coating is specifically designed to block a certain wave length of light. Although quartz is substantially more expensive, the material is mandatory when the photomask will be used with a deep UV exposure system or in situations where substrate expansion characteristics are critical.

Alignment and placement of the pattern on the substrate is often crucial. Patterns sometimes must be placed within +/-0.2 microns of relative or true position. Photo Sciences uses automatic pattern recognition to achieve the tightest tolerances possible.