Precision X-Y positioning systems using linear induction motors

An X-Y stage for use principally in the semiconductor industry, for electron beam lithography tools and wafer steppers, is described. The stage features a moving puck which is supported by air bearings on a flat baseplate and is driven by on-board linear induction motors which thrust against the baseplate. The stage position is measured by laser interferometers and is controlled by a digital servo system which computes the drive to the linear motors in real time. The design and measured performance of the induction motors is described together with their 8 channel switch mode drive amplifier