| 摘要 |
PURPOSE:To detect with the same sensitivity a scattered light from particles on the surface of substrates whose optical reflection factors are different, by correcting in advance the detection sensitivity of a light detecting system in accordance with an optical reflection factor on the surface of the substrate. CONSTITUTION:By a laser light emitted from a light source 11, the surface of the substrate to be inspected 12 is scanned successively. A regularly reflected light 13 from the surface of the substrate 12 is emitted to the outside from one opening hole part of an integrating sphere 14. Also, a scattered light 15 is integrated by the integrat ing sphere 14 and led out to the outside from other opening hole part. the scattered light 15 is made incident on the light-receiving surface of a PMT (a photoelectro- multiplier tube) 16, converted to a voltage signal corresponding to its light intensity, amplified by a heal amplifier 17 and supplied to a measuring circuit, and dust, etc., exceeding a specified particle diameter are detected. On the other hand, an averaging part 18 averages the output voltage of the head amplifier 17 in a prescribed period, and holds it. A high voltage power source control part 19 supplies a control signal corresponding to a holding voltage by the averaging part 18, to a high voltage power source part (HV) 20, and the HV 20 supplied a DC high voltage set in accordance with a control signal, to the PMT 16. |
