| 摘要 |
PURPOSE:To realize an alignment with high accuracy by averaging with weighting the positions of the center of gravity in a pattern detecting windows set before and after the skewness value has a zero-cross with the corresponding skewness value to obtain the center position of a pattern. CONSTITUTION:The video signal of a code number 1 obtained by an image pick-up means is integrated in the direction 12Y by a 2-dimensional window 4. Thus an integration signal Pi8 is obtained and a contrast C is obtained against the signal Pi8 with the signals less than the threshold level K deleted as the objects out of measurement. A measuring window of width 7 is set and the skewness Sj is obtained while shifting the measuring window within the signal Pi8 to obtain a zero-cross area together with the area of S>K and the area of S<K respectively. Thus the symmetrical properties are obtained. When the symmetrical properties are confirmed, it is decided that the zero-cross point at the center of the symmetrical properties is coincident with a point near the center of a wafer pattern. |
