Patent ID: 6760100
Filing Date: 2004-07-06
Classification: G01N

Abstract:
A method for classifying defects occurring at or near a surface of a smooth substrate, comprising:(a) defining a plurality M of different idealized types of defects that can occur at the surface of the substrate, such that a given defect occurring at the surface can be described at least approximately by a size parameter d and by one of said idealized types; (b) providing a database containing a plurality N of different sets of data for each said idealized type of defect, each set of data comprising a magnitude S of a signal from a light collector versus size parameter, the N different sets for each defect type corresponding to N different predetermined test configurations in which a beam of light having predetermined characteristics is impinged on the surface of the substrate at a predetermined incident angle and light emanating from the surface is collected by the light collector at a predetermined location above the surface and the intensity of the collected light is measured, the different predetermined test configurations being the same for each idealized defect type; (c) testing the substrate with each of said N different predetermined test configurations so as to derive N signal magnitudes S1 to SN for a defect to be sized and classified; (d) for each of the M idealized defect types, using the database therefor to determine a plurality of sizes d1 to dN corresponding to the N signal magnitudes S1 to SN; and (e) classifying the defect as being of the idealized type having the smallest spread between said plurality of sizes d1 to dN and determining a size of the defect based on an average of said sizes.