| 摘要 |
PURPOSE:To realize the good signal-to-noise ration of detection for a film- deposited wafer of various thicknesses and materials by installing a means to switch a wavelength of the light which is used to detect a foreign substance. CONSTITUTION:A means to switch a wavelength of the light to be used for detection of a foreign substance is installed at an inspection system, of the foreign substance, where the light illuminates the surface of a wafer 12 and the foreign substance on the surface of the wafer 12 is detected on the basis of a photoelectric conversion signal of the scattered light. For example, the surface of a wafer 12 is scanned in a spiral manner or in a plane manner by using a laser beam of one wavelength lambda1: the scattered light from the surface of the wafer enters a optoelectric transducer 24; when a photoelectric conversion signal exceeds a threshold level TH, a detection signal of the foreign substance is generated. If the result of the inspection of the foreign substance by using the wavelength lambda1 is abnormal, the other wavelength lambda2 is designated by an operating unit; a laser oscillator 16 of the designated wave-length is actuated; the laser beam of the wavelength ALPHA2 illuminates the surface of the wafer; the foreign substance is detected and judged on the basis of the level of the photoelectric conversion signal of the scattered light.
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