| 摘要 |
<p>An apparatus used to inspect patterned wafers (10) and other substrates with periodic features for the presence of particles, defects and other aperiodic features in which a spatial filter (26) placed in the Fourier plane is used in combination with either broadband illumination, angularly diverse illumination or both. Embodiments are described that illuminate a patterned substrate using (1) a single monochromatic source (210) with a slit-shaped aperture stop (207) for angularly diverse illumination, (2) a single broadband source (512) with a pinhole aperture stop (510) for broadband illumination, (3) a single broadband source (14) with a slit-shaped aperture stop (20) for both broadband and angularly diverse illumination, or (4) multiple sources (205, 210) with an aperture stop (20, 207) for each source for at least angularly diverse illumination. The spatial filters are characterized by opaque tracks (56; 656) in an otherwise transmissive filter for blocking the elongated bands produced by diffraction from the periodic features on the illuminated substrate.</p> |
