Movable support in a vacuum chamber and its application in lithographic projection apparatuses

摘要

An object table is supported in a vacuum chamber by an elongate beam or beams extending though elongate slots in opposite walls of the vacuum chamber. Displacement of the beam in two orthogonal directions is achieved by displacing the beam laterally and longitudinally. The elongate slots are sealed by sliding plates supported by a gas bearing. The beam is driven longitudinally by linear motors acting against between a balance mass and the beam. The beam is driven laterally by linear motors acting between a balance mass and the sliding plates. The two balance masses may be separate or combined.