| 摘要 |
PURPOSE:To improve accuracy in detecting the relative position of both a wafer mark and an index mark by a method wherein the positions of both mark images and a detection region are relatively moved to a direction to cross a scanning line without changing the relative positional relation between the wafer mark and the index mark. CONSTITUTION:At the time of performing alignment, a rectangular sampling region 23 enclosed by dotted lines is set as an image signal detecting region at first. Then scanning for image detection is performed along a horizontal direction of the sampling region 23 and further an image detection signal averaged by summing up every scanning position on the respective scanning lines in a vertical direction is obtained. The ratio in contrast of detection signals of an index mark image 30 and a wafer mark image 25 is calculated, and according to the ratio the sampling region 23 is moved. Therefore the contrast of the averaged detection signal varies so that difference in contrast of detection signals from both mark images becomes small, thereby improving accuracy in relative position detection. |
