Patent ID: 7652776
Filing Date: 2010-01-26
Classification: G03F,H01L

Abstract:
1. A method for overlay measurement, comprising steps of: (a) forming a material layer comprising a first grating structure and a second grating structure being overlaid with each other and having with different periods, wherein there is an interval gap in each of the first grating structure and the second grating structure; (b) measuring an optical intensity distribution of an optical image around the interval of the material layer; (c) determining a merit value based on the optical intensity distribution; (d) changing the distance between the center of the interval on the first grating structure and the center of the interval on the second grating structure; and (e) repeating from step (a) to step (d) to obtain a merit relation based on the plurality of merit values resulting from step (a) to step (d).