| 摘要 |
PURPOSE: To detect with precision defects on the surface having repeated pattern by pouring monochrome light ray on a wafer surface at a specified incident angle. CONSTITUTION: A monochrome light ray from a helium-neon laser 110 is reflected on a surface mirror 112, and magnified with a beam magnifier 114, and, through a polarizing filter 315, incident on the surface of a semiconductor wafer 116 at an incident angleθ, for example 45 deg.. Though a main part of the light ray is reflected from the sight field of an image system, the light ray scattered almost vertical to the surface of wafer 116 is gathered with a Fourier transform lens 118, and when Fourier-converted at a flat surface of one focal length behind the lens 118. A Fourier space filter 120 is assigned on the Fourier conversion surface, for avoiding space frequency component of the scattered light corresponding to a repeated pattern. The light ray which has passed through the filter 120 is restored to a parallel light ray with a lens 122, and, through a magnification optical mechanism 126, sent to a video camera 128, so that the image wherein fine particles and defects in the repeated pattern are intensified is formed.
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