| 摘要 |
PROBLEM TO BE SOLVED: To locate even a mark signal from a high resolution optical system accurately by utilizing a mask of such shape as the signal value at one- dimensional signal part corresponding to the border part varies slowly when the mark is located from the one-dimensional signal obtained by accumulating the two-dimensional image of mark in one direction. SOLUTION: Image of a wafer mark WM is converted optoelectrically through an image pickup unit 107 and then converted through an A/D converter 108 into a series of two-dimensional digital signals. The image of wafer mark WM, converted into digital signals, is subjected to moving average processing in Y direction within a processing window by means of an accumulator 109 and the two-dimensional image signals are converted into an accumulated waveform. A locator 110 locates the wafer mark WM with respect to a reference position in image area from the accumulated waveform. In the mark image input step 1, a plurality of marks having slowly varying signal waveform at the border are used as a wafer mark WM being formed on the image plane of image pickup unit 107 at the time of accumulation. |
