| 摘要 |
PURPOSE:To improve the accuracy of alignment by relative alignment of interference fringes and gratings on a substrate, by using Moire interference fringes between two luminous fluxes of diffraction light diffracted by the gratings. CONSTITUTION:A laser beam 8 is projected on an alignment grating 9 being a mark on a mask 2. Diffraction light is reflected in the order of a plane mirror 3, a concave mirror 4, a convex mirror 5 and the plane mirror 3. By the effect of a spatial filter 15, the + or - first order light only are focused on a wafer 7, and generate interference fringes. The amount of alignment difference X between interference fringes 18 and a grating 12 is measured with the light intensity of Moire fringes of diffraction light 19. That is, the intensity of Moire light, wherein diffraction light of the first order light and re-diffraction light of the first order light overlap and interfere with each other, corresponds to the amount of alignment difference, and the measurement of high position accuracy is enabled. |
