| 摘要 |
A semiconductor wafer, which has a diffractive grating array acting as a alignment mark, is irradiated with a polarized light beam while relatively moving the semiconductor wafer and the polarized light beam. The polarized light beam consists of a polarized component which vibrates in a direction substantially perpendicular to the diffractive grating array. A diffractive light beam from the wafer is received to measure the light intensity thereof. On the basis of the measured intensity, the diffractive grating array is detected. Thus, it is possible to accurately detect the alignment mark.
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