Patent ID: 7869025

Claim:
An optical inspecting method comprising steps of: holding an object to be inspected on a stage; illuminating obliquely a surface of the object on the stage with an oblique illumination system; detecting a luminous intensity of scattered light of high-angle generated by the object illuminated obliquely, using a high-angle detection system orientated to have a high-angle with respect to the surface; detecting a luminous intensity of scattered light of low-angle generated by the object illuminated obliquely, using a low-angle detection system orientated to have a low-angle with respect to the surface; and classifying a defect on the object according to a difference between the luminous intensity detected by the high-angle detection system and the luminous intensity detected by the low-angle detection system, wherein: the defect is classified to be a void when the luminous intensity detected by the high-angle detection system is greater than the luminous intensity detected by the low-angle detection system, the defect is classified to be a scratch when the luminous intensity detected by the low-angle detection system is greater than the luminous intensity detected by the high-angle detection system, and the defect is classified to be a particle when the difference between the luminous intensity detected by the low-angle detection system and the luminous intensity detected by the high-angle detection system is not more than a predetermined value.