Definition of Step and scan

Step and Scan
a step and scan system steps to different locations on a wafer for exposure similar to a step and repeat system, except a step and repeat system exposes a whole area at once and a step and scan system scans light through a slit across the area to be exposed. Difficulties in manufacturing large lens with high resolution limit step and repeat lens systems to approximately 25 x 25mm exposure areas, referred to as fields. Step and scan can produce an approximately 25mm wide field but then scan to a length of approximately 35mms.