| 摘要 |
PURPOSE:To detect the defect on the subject wafer by a method wherein the pattern repeated part is imaged on the same picture twice or more and the signals on the repeated part are compared with each other. CONSTITUTION:The X and Y directions of the difference in luminance of the two picture elements separated by 4-6 picture elements striding over the defect and the boundary are computed, a boundary depicting signal is formed and a bit of signal is binderized base on the prescribed threshold value. A decision frame 3 for an fXg picture element is provided on the adjoining repeated part 1, while it is cut at fXg by shifting by a repetition periodicity T and a decision frames 3X and 3Y are formed. Figures P and Q, which will be obtained from the set of value that has been transformed into one bit from the corresponding picture element in the frame, are determined, the threshold value Rth is provided by computing defect rank R=P-Q and R=O (P<Q), the occurrence of errors and the like of the width of the repeated pattern 1, the repetition periodicity T and the like are prevented and decision is given as a defect 2 when it is in excess of R. The number of the decision frame (number of R) will be (v-f+1)X(h-g-k+1) when the picture elements are vXh per picture, fX in the decision frame and k in the repetition periodicity T respectively. Thus a decision can be given as a defect by comparing the above two repetition sections resulting in the discored between the two. |
