Patent ID: 7106432
Filing Date: 2006-09-12
Classification: G01N

Abstract:
1. A dark field surface inspection tool comprising: a) illumination source for directing a light beam onto an inspection point on a work piece, thereby generating a light scattering pattern associated with surface characteristics of the inspection point; b) scanning element that enables a plurality of inspection points on the work piece to be scanned, thereby generating light scattering patterns associated with each of the inspection points; c) photodetector array comprised of a plurality of photosensitive elements arranged to receive light from a light scattering pattern, so that a sample image of the light scattering pattern can be captured for each inspection point wherein the photosensitive elements of the photo detector array are arranged in a substantially hemispherical configuration relative to the inspection point; and d) circuitry for comparing the sample image with a reference image for the same inspection point, said comparison enabling the identification of defects at the inspection point wherein said comparison involves determining the darkest pixels in the reference image for a given reference point and comparing only the darkest pixels with corresponding pixels in the sample image to determine whether a defect is present at the inspection point of the sample image.