Patent ID: 7408643
Filing Date: 2008-08-05
Classification: G06T,H01J

Abstract:
1. A method for measuring a magnification of a secondary optical system in an image projection type inspection apparatus, in which a surface of a substrate including a chip formed therein is inspected by using a beam, said method comprising steps of: (a) placing said substrate so that said chip is positioned within a field of view subject to the inspection; (b) irradiating a rectangular beam onto a characteristic pattern on said substrate to detect back-scattered electrons or secondary electrons from said substrate by a detector, thereby obtaining a two-dimensional image; (c) storing a coordinate of the stage (Xc, Yc) when said two-dimensional image is obtained in said step (b) by a laser interferometer; (d) moving the stage by a certain distance and thus moving said characteristic pattern, within said field of view; (e) performing the same operation as said step (b) so as to obtain the two-dimensional image of said characteristic pattern in said moved position; (f) storing a coordinate of the stage (Xf, Yf) when said image has been obtained in said step (e) by said laser interferometer; (g) applying a pattern matching between a portion of said image obtained in said step (b) and said image obtained in said step (e) to calculate a displacement between said two images in the X- and Y-directions (ΔX pixel, ΔY pixel); (h) calculating a difference between said coordinate (Xc, Yc) stored in said step (c) and said coordinate (Xf, Yf) stored in said step (f), defined by (Xf−Xc) or (Yf−Yc); (i) calculating a size per pixel, (Xf−Xc)/ΔX or (Yf−Yc)/ΔY, as a magnification of a projection optical system.