Integrated Circuit Visual Inspection Using Spatial Filtering

Internal visual inspection of integrated circuits (ICs) as now implemented is highly subjective, and the quality of the inspected product is not always satisfactory. As an approach to reducing the subjectivity of visual inspection, optical spatial filtering has been used to produce an IC defect image. The inspector is presented with an IC image in which most of the complex IC pattern detail is suppressed while the image of a defect is enhanced. Results range from excellent for metalization defects on optically smooth circuits to poor for certain low contrast defects on circuits with a high degree of surface roughness.