Patent ID: 6603589
Filing Date: 2003-08-05
Classification: G01N,Y10S

Abstract:
A method to compare similar physical areas of an inspection area of a sample using a scanning arrangement, the inspection area having a periodic pattern having a repeat vector, the scanning arrangement having a stage configured for mounting the sample thereon, the scanning arrangement having a drive mechanism and at least one circular scanner, the circular scanner having at least one scanning head and an axis of rotation, the scanning head performing a circular scanning motion about the axis of rotation, the drive mechanism configured to provide relative movement between the stage and the axis of rotation, the method comprising the steps of:(a) scanning the inspection area by a combination of circular scanning of the scanning head and by generating relative movement between the stage and the axis of rotation so as to generate a scanning pattern which includes a plurality of curved scanning paths wherein pairs of the curved scanning paths are related by an integer multiple of the repeat vector; and (b) comparing at least one of said pairs of the curved scanning paths by a pixel to pixel comparison.