| 摘要 |
PURPOSE:To detect defect in a pattern easily with high accuracy by making two light beams incident exactly to the same position of the patterns of two very large scale integrated circuit (VLSIs) or the like. CONSTITUTION:Transparent parallel plane plates 12A and 12B are disposed in the optical path of at least one of two objective lenses 11A and 11B, and these are disposed freely turnably around the axial lines A-A, B-B perpendicular or approximately perpendicular to the optical path by means of knobs 13A, 13B. If the one plate 12A is turned by the same, one light beam is deflected slightly in a Y direction by the refraction effect thereof and if the other plate 12B is turned, the other light beam is deflected slightly in an X direction by the refraction effect thereof. Thus, the same positions of the two adjacens on a photomask 14 ar inspected simultaneously. The beams of the light transmitted through the respective patterns are detected with photodetectors 15A, 15B, and are compared in a signal processing circuit 16, whereby the defects of the patterns are detected with high accuracy. |
