| 摘要 |
PURPOSE:To perform automatically regulation of referential levels, and to enable to detect surely the positions of the alignment marks of a mask and a wafer by a method wherein the intervals of the peaks of reflected beams are measured by comparing the previously set respective slice levels and the signals of reflected beams from recognition marks corresponding to the slice levels thereof. CONSTITUTION:Slice levels at a second measurement mode are not fixed, and the slice level is set separately every peak. Accordingly the peak value is detected in regard to every signal S71, S75, S72... of respective positioning marks at a first measurement mode, and the slice level is set every signal. At second measurement mode, timing to pass the slice levels is masured by comparing the slice level values of respective alignment mark detection signals stored at the prescribed addresses in a memory and the alignment mark detection signals corresponding thereto. |
