Patent ID: 7313873

Claim:
A surface position measuring method, applied to an exposure apparatus for exposing a surface of a substrate to light through a projection optical system, for measuring a position of the surface of the substrate, wherein measurement light is obliquely projected onto the substrate surface and the measurement light on that surface is detected and wherein, on the basis of a position of the detected measurement light and a predetected offset, the position of the substrate surface with respect to a direction of an optical axis of the projection optical system is measured, said method comprising steps of: memorizing, as a first position, a position of a measurement point on the substrate while using, as a reference, a reference mark provided on a substrate stage which is configured to hold and move the substrate; measuring, in accordance with information concerning the memorized first position and in relation to the measurement point, the position of the measurement light as a first measurement position; rotating the substrate by 180 degrees in a plane perpendicular to the optical axis; memorizing, as a second position, a position of the measurement point on the rotated substrate with reference to the reference mark; measuring, in accordance with information concerning the memorized second position and in relation to the measurement point, the position of the measurement light as a second measurement position; and detecting the offset at the measurement point, on the basis of the first measurement position and the second measurement position.