Importance

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Abstract

According to the invention, the surface of the Sic substrate or the epitaxial layer formed on the Sic substrate using the optical apparatus including the differential interference optical system. The reflected light from the surface of the Sic substrate or the epitaxial layer is received by the line sensor (23), and the output of the line sensor is supplied to the processor (11). The processor comprises means for forming the differential interference contrast image of the surface of the Sic substrate. The differential interference contrast image of the surface of the Sic substrate is supplied to the defect detection means in order to detect the defects formed in the substrate. The image of the detected defect is supplied to the defect classification means (36) to classify the type of the defect based on the shape and luminance distribution of the defect image. The defect classification means comprise a first classifying means (50) for classifying the defect image having specific shape and a second classifying means (51) for classifying the defect image having a spot shaped dark image or the luminance distribution of a bright image portion and a dark image portion.

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First Claim