Exposure apparatus and device manufacturing method

Abstract

An exposure apparatus or a device manufacturing method, wherein a focus measuring device measures a best focus position upon projecting and exposing, through a projection optical system, a pattern of an original plate onto a substrate placed on a movable stage, by obtaining predetermined estimating information indicative of a blur degree of an image being observed, when observing a reference mark on the movable stage or the surface of the substrate by the focus measuring device, while changing a relative position between the movable stage and the projection optical system toward an optical axis direction of the projection optical system. This exposure apparatus or device manufacturing method controls whether or not the best focus position is measured, based on (i) an elapsed time after a last projection and exposure or (ii) the estimating information obtained at a predetermined time by the focus measuring device and estimating information obtained at the time of measuring the best focus position at the preceding time.

Dependencies are inferred from the claim text.