PARTICLE-DETECTION TECHNOLOGY ON WAFER USING SPATIAL FILTER

An automated particle detection system for patterned wafers has been d eveloped. A specific area of the wafer is illuminated with a laser at 45 degrees diagonal in reference to an orientation-flat shaped on the wafer. The diffracted light is detected by an objective lens. The sign al obtained by the memory-mat on a wafer is reduced to 1/8-1/15 by set ting the printed spatial filter on the conjugate image plane of a Four ier transformed plane in an objective lens. By using the subtracted im age signal with the spatial filter, 0.5 mu m standard particles on a m ulti-layer pattern can be detected.