Patent ID: 6958808

Claim:
An exposure apparatus comprising: an illumination source that has an on position and an off position; and a stage assembly that moves a device relative to a stage base so that the device is properly positioned for one or more operations performed by the exposure apparatus, the stage assembly comprising: a stage that retains the device; a stage mover assembly connected to the stage, the stage mover assembly generating reaction forces; a reaction mass assembly coupled to the stage mover assembly, the reaction mass assembly reducing the reaction forces that are transferred to the stage base; a reaction mover assembly connected to the reaction mass assembly, the reaction mover assembly moving the reaction mass assembly relative to the stage base; and a control system connected to the reaction mover assembly, the control system controlling excitation of the reaction mover assembly during the one or more operations for an individual device based upon the on position and the off position of the illumination source; wherein in the on position, the illumination source directs a beam of light energy towards the stage assembly, and in the off position, the illumination source does not direct a beam of light energy towards the stage assembly.