Balanced positioning system for use in lithographic apparatus

摘要

A balanced positioning apparatus comprises a balance mass which is supported so as to be moveable in the three degrees of freedom, such as X and Y translation and rotation about the Z-axis. Drive forces in these degrees of freedom act directly between the positioning body and the balance mass. Reaction forces arising from positioning movements result in corresponding movement of the balance mass and all reaction force are kept within the balanced positioning system. The balance mass may be a rectangular balance frame having the stators of two linear motors forming the uprights of an H-drive mounted on opposite sides. The cross-piece of the H-drive spans the frame and the positioned object is positioned within the central opening of the frame.