| 摘要 |
PURPOSE:To enhance the allgning accuracy, by passing all the light, which is reflected from the portion of the wafer surface where a periodically structured aligning mark does not exist, through a light screening plate; and passing only zero-order light from the portion where said mark exists. CONSTITUTION:At the pupil position of the optical aligning system in an IC projection exposure apparatus, is provided a light screening plate 5a which restricts the illuminating luminous flux extended in a belt shape, so that said luminous flux crosses at a right angle with the periodic direction of a periodically structured aligning mark 11 on a wafer 3, as shown in the figure. The illuminating light flux, which forms a slit image is made to pass through the central portion of the pupil; so that all the light, which is reflected from the portion of a wafer where the aligning mark 11 does not exist, is returned to a light to a light receiving element 8. Of the reflected image of the projection of the slit 6 from the portion where the aligning mark 11 exists, the diffracted light of the + or - first order or above is screened by the light screening plate 5a, and only the zero-order light is passed and received by the light receiving element 8. |
