X-Y-theta Stage assembly.

摘要

An improved gas bearing X-Y-ϑ stage assembly is disclosed which has a base (18), a stage element (12) with three retroreflectors (78,80,82) fixedly mounted thereto and movable by a X-,Y-, ϑ-linear motor (14), and a control system for controlling the movement of the stage element (12). The stage element (12) is movable by a X-,Y-,ϑ-linear motor (14). The control system is made up of three interferometers (72,74,76) for measuring parameters associated with changes in position of the three retroreflectors as the stage element (12) moves. Also, the control system includes a transport system (100, 106) for moving the three interferometers (72,74,76) to maintain optical coupling between the interferometers and retroreflectors (78,80,82). In addition, the control system includes control circuitry for causing the stage element to move to a preselected X-Y-ϑ position in response to signals from the interferometer measuring systems (78,80,82). A first interferometer (76) is moved linearly by the transport system on a gas bearing slide (106) in a direction parallel to the Y-axis of the system, while second and third interferometers (72,74) are moved together on a second gas bearing slide (100) parallel to the X-axis of the system.

A computer is used to calculate displacement informa­tion relative to the stage in order to provide feedback control signals to the stage element. A preferred use of the stage assembly is to step and position a semiconductive wafer (13) which is mounted on the stage element (12) under an imaging lens of a step- and repeat-camera.