Measurement of geometrical shapes, especially alignment markings, on a semiconductor wafer using an optical system, whereby an optimum contrast value is used for a detected shape if a reference threshold cannot be obtained

摘要

Method for measuring a geometric shape in or on a semiconductor wafer using an optical measurement system with a light source and an optical system has the following steps: recording an image of the geometric shape on the wafer; determination of a contrast value for the shape; comparison of the contrast value with a reference value; repetition of the imaging steps if the contrast value is less than the reference value and evaluation of the recorded image, whose contrast value corresponds at least to the reference contrast value or whose contrast value is the highest. An independent claim is made for an optical measurement system for measuring a geometric shape in or on a semiconductor wafer.