Patent ID: 9194692
Filing Date: 2015-11-24
Classification: G01B,G02B,G03F

Abstract:
1. A method for measuring an undercut of bi-layer structures on a wafer, the method comprising: performing a first scan of a first bi-layer structure having an upper layer disposed on a lower layer with a microscope using a first scan range corresponding to a first depth of scanning, wherein the microscope is configured for white light interferometry; generating a first interferogram using data from the first scan; performing a second scan of the first bi-layer structure with the microscope using a second scan range corresponding to a second depth of scanning different than the first depth of scanning; generating a second interferogram using data from the second scan; determining a first distance between first features of the first interferogram, the first features corresponding to respective physical edges of one of the upper layer or the lower layer of the bi-layer structure; determining a second distance between second features of the second interferogram, the second features corresponding to respective physical edges of the other of the upper layer or the lower layer of the bi-layer structure; and calculating a width of the undercut based on the first distance and the second distance.