AUTOFOCUS METHOD AND APPARATUS FOR WAFER SCRIBING

摘要

A method and an apparatus perform real time autofocus for a wafer scribing system. The method and apparatus uses polarized light (42) directed to the surface (50) of the wafer (10) directly under the objective lens (26) for the scribing laser beam at a grazing angle. The light reflected from the wafer is filtered (56) to remove light from the scribing laser beam and then focused on a position sensitive device (58) to measure the distance from the objective lens to the wafer surface.