Patent attributes
Inspection of objects such as semiconductor wafers can include comparisons of shapes between inspection and reference images. As part of the inspection process, relative values may be assigned to pixels within each image based on comparison of such pixels to neighboring pixels. For instance, the pixels may be ranked by relative brightness in each image. Alternatively, directional vectors may be defined based on slopes between pixels and their neighbors. Various comparison metrics may be utilized to determine the degree of correlation between the relative values for pixels in the inspection image and corresponding pixels in the reference image. Relative values may be combined with conventional techniques as part of an inspection process. The inspection may be performed using an optical inspection tool that uses conventional techniques to identify defect candidates, with relative value analysis performed on areas containing defect candidates to confirm or deny the existence of a defect.
