A perspective on stage dynamics and control

In the semiconductor industry, a wafer stepper is used to expose the pattern on a mask (‘reticle’) onto a wafer. Accurate positioning of the reticle and the wafer is of crucial importance for creating a working IC. This paper reflects on the stage dynamics and control design in Stepper technology, introduces the modifications needed to successfully implement Scanner technology, and shows the further improvements in dualstage TWINSCAN systems.