| 摘要 |
PURPOSE:To prevent the degradation of the precision of an autoalignment mark by providing an index part having distinct edges and a shielding part extended surrounding the index part. CONSTITUTION:When the auto-alignment mark is scanned with a laser beam, diffracted lights b2-b4 are generated. The diffracted light b1 in a shielding part 22 has the intensity changed with time because it interferes with a reflected light b2 from a wafer. The intensity of the diffracted light b3 of an index part 21 is not changed because it does not interfere with the reflected light from the wafer. Consequently, intensities of photoelectric converted signals S2, S4, and S6 are not changed with time and are stable though those of photoelectric converted signals S1, S3, S5, and S7 are changed with time. Only edge signals S2, S4 and S6 which are not affected by the interference due to the reflected light from the wafer and have stable intensities are used to measure intervals of marks, and precise auto-alignment is performed. Thus, the precision of auto- alignment is improved. |
