Thin Film Magnetic Head Wafer Inspection Technique Using Geometrical Feature Based Image Comparison

A reliable inspection system for thin film magnetic head (TFH) patterns on a ceramic wafer substrate has been developed. Since the TFH patterns have a great variety of shapes, the inspection criteria becomes much more complex; that is, the fatal defect size and orientation are defined according to pattern shape. To overcome this problem, we have developed a method that can detect fatal defects by examining defect size according to pattern size and pattern direction, which are stored as images. In this paper, the inspection algorithm for TFH patterns is discussed and we also mention the hardware implementation of the inspection system. Experimental results show the validity of our method. fective products. However, the TFH patterns have a great variety of shapes, and the criteria for inspecting the TFH pattern has become much more complex. Therefore, a visual inspection system is required to vary its sensitivity according to the pattern shape. Concerning TFH pattern inspection, Wakisaka et al[l] have reported an inspection system which detects defects preventing false alarms caused by the pattern's surface texture. Matsuyama et a1[2] have reported an inspection system which detects defects within/on a protection layer using optical defect enhancement and gray scale image processing. However, these systems are expensive and were not designed to cope with the pattern varieties. We have developed a new inspection system to satisfy this requirement.