| 摘要 |
PURPOSE:To perform high-precision positioning operation by detecting the shape of a positioning grating formed on a wafer and correcting the quantity of an occurring error in positioning by using the grating shape. CONSTITUTION:A reticle 14 is arranged between an illumination optical system 13 and the 1st Fourier transform lens 15 and an image emitted as a secondary light source is converged temporarily by the 1st Fourier transform lens 15 and further passed through the 2nd Fourier transform lens 15 to project an image of the pattern of the reticle 14 on the semiconductor wafer. When the 1st Fourier transform lens 15 and the 2nd Fourier transform lens 17 are equalized in focal length, the image of the pattern on the reticle is projected to life size. When the 1st and the 2nd Fourier transform lenses 15 and 17 are made different in focal length, the image is projected while reduced. The diffracted light of the pattern on the reticle is distributed spatially on the rear focal plane of the 1st Fourier transform lens and a spatial filter 16 is arranged to filter the pattern image formed on the reticle in a spectral plane, thereby projecting the light on the surface of the wafer W. |
