Patent ID: 6577384
Filing Date: 2003-06-10
Classification: G01B,G01N,H01L

Abstract:
An apparatus for evaluating the characteristics of a sample wherein the sample includes a measurement area defined by a region having characteristics different from the surrounding region, comprising:a probe beam of radiation which is focused to a spot on the surface of the sample and reflects therefrom and wherein the size of the probe beam spot is similar to the size of the measurement area; an optical detector for monitoring the reflected probe beam and generating output signals in response thereto; a movable stage for supporting the sample in a manner to translate the sample with respect to the probe beam such that the probe beam spot strikes the sample at a location substantially in the center of the measurement area and at locations on either side thereof allowing optical measurements with the optical detector to be made at a plurality of the locations; and a processor for computing the characteristics of the sample for each of the measurement locations and for determining an extremum in the computed characteristics to identify the measurement location best corresponding to the center of the measurement area.