Particle detection technology opn wafer using spatial filter

An automated particle detection system for patterned wafers has been developed. A specific area of the wafer is illuminated with a laser at 45° diagonal in reference to an orientation-flat shaped on the wafer. The diffracted light is detected by an objective lens. The signal obtained by the memory-mat on a wafer is reduced to 1/8-1/15 by setting the printed spatial filter on the conjugate image plane of a Fourier transformed plane in an objective lens. By using the subtracted image signal with the spatial filter, 0.5μm standard particles on a multi-layer pattern can be detected.