Patent ID: 6072915
Filing Date: 2000-06-06
Classification: G03F

Abstract:
Process for pattern searching, in which the position coordinates of patterns formed of straight lines are searched on a workpiece with a surface roughness, comprising the steps of:storing images of said patterns, which images are formed only by parts of straight lines, as light-dark signals;determining segment lengths of lines to be integrated based on a contrast of said pattern with respect to a reference level and on said surface roughness of said workpiece;integrating the light-dark signals along lines which extend in directions which are each parallel to a respective one of the lines of the patterns and which are of the segment lengths determined in said determining step, by which integration signals are determined which correspond to said lines;producing differential signals which represent a mathematical differentiation of the integration signals and determining actual peak positions of the differential signals; anddetermining pattern positions on the basis of the peak positions which were determined; wherein the step of determining segment lengths of lines to be integrated is performed in accordance with the relationship:L>.vertline..DELTA.2/.DELTA.1.vertline.d.multidot.kwhere L is the segment length, .DELTA.1 is a contrast difference of the pattern with respect to the reference level and .DELTA.2 is a contrast difference of black cloudiness and milky cloudiness observed as a result of the surface roughness of the workpiece with respect to the reference level, d is a grain size of said black and milky cloudiness, and k is a coefficient corresponding to said surface roughness.