METHOD AND APPARATUS FOR DETECTING FOREIGN MATTER ON BOTH SURFACES

摘要

PURPOSE:To provide a foreign matter detecting method and apparatus capable of inspecting the minute foreign matter bonded to the surface and rear of a transparent substrate in distinction from each other. CONSTITUTION:The surface and rear of a transparent substrate 21 having a circuit pattern formed to the surface thereof are subjected to condensed beam spot illumination by the laser illumination beams from a surface illuminating condensing optical system 90 and a rear illuminating condensing optical system 85 in such a state that both systems are inclined with respect to the direction vertical to the surface of the transparent substrate 21 and the respective condensed beam spots and an object to be inspected are relatively scanned by a scanning means and the respective scattering beams from the foreign matter bonded to the surface and rear of the substrate 21 are condensed by both optical systems 90, 85 and the condensed beams are detected by a surface photoelectric conversion means and a rear photoelectric conversion means. On the basis of the signals detected from both means, foreign matter bonded to the surface and one to the rear of the substrate are separately detected.