Precision stage interferometer system with air duct

摘要

A local gas duct directs a temperature-controlled stream of gas across two perpendicular sets of interferometer beams which are used to measure the two dimension (X-Y) position of a precision stage in e.g. an optical lithography stepper or step and scan system, or in any other precision coordinate measuring machine. By thereby providing an additional single gas flow which is azimuthally directed across both the X and Y direction interferometer beams, the precision of the interferometric measurement is maximized. In addition, a second flow of gas is directed downvards from the local gas duct, thus providing sufficient gas circulation onto the stage when the stage is directly beneath the local duct, even though in that location the stage is otherwise blocked from receiving the main gas flow through the chamber. <IMAGE>