PURPOSE: To offer the foreign matter detection optical system which detects only foreign matter without detecting the writing pattern of a reticle by utilizing the feature of variation of scattered light from the wiring pattern with the projection direction of a laser beam by a reticle foreign matter inspection device.
CONSTITUTION: Two projection systems project two laser beams L and L2 which differ in wavelength on an inspection point on the surface of the reticle mask 1 in mutually opposite direction at a low angle; and the laser beam is scattered by the foreign matter equally in all directions and the scattered light beams of both the laser beams are nearly equal, so the foreign matter can excellently be detected from the product of data of both the scattered light beams. In the case of the wiring pattern 1b, one scattered light beams becomes zero, so the product of the both is calculated and equalized to zero not to detect the wiring pattern. Consequently, the influence of the wiring pattern is eliminated to improve the detection performance for the foreign matter on the reticle mask.
ASAMI KOICHI
NOGUCHI MINORU
SHISHIDO HIROAKI
HITACHI LTD