Surface position measuring method and apparatus

Abstract

A measuring apparatus for measuring a position of a surface of an object while the object is scanned in a scanning direction in an X-Y plane. A detecting unit detects the position of the surface of the object in a Z direction perpendicular to the X-Y plane, a stage scans the object relative to the detecting unit in the scanning direction, and a controller causes the stage to pre-scan the object relative to the detecting unit in two scanning directions, in the X-Y plane, opposite to each other, to detect, using the detecting unit, with respect to each of the two scanning directions, a position of the surface in the Z-direction for each of the same detection points on the surface, to determine, with respect to each of the two scanning directions, a reference surface based on the detected positions of the surface, to calculate an offset value, which is a difference between the detected position and a position of the reference surface in the Z-direction for each of the same detection points with respect to each of the two scanning directions, to calculate a correction value for correcting the calculated offset value in accordance with a corresponding one of the two scanning directions based on a difference, in the Z-direction, between positions of the determined reference surfaces obtained with respect to the two scanning directions.