A reference mark used in the alignment of the several photomask layers required for a single device or circuit.

mark or target on a reticle or mask that is used to achieve alignment. For example, a wafer might have a cross printed on it from a previous layer, and a reticle might have a cross designed to fit inside the cross already on the wafer. When the smaller cross fits within the larger cross, the reticle is aligned to the wafer.