Method of detecting and classifying scratches, particles and pits on thin film disks or wafers

Abstract

Scratches, pits and particles which are smaller or larger than the beam size may be measured and identified by a dual beam technique. This invention uses a pair of orthogonally oriented laser beams, one in the radial and one in the circumferential direction. The scattered light from radial and circumferential beams allows the detection and classification of particles, pits and scratches.

1 . A method for measuring a defect on a surface of an object, comprising: 
 directing a first light beam in a first plane of incidence toward a first position on the object;    directing a second light beam in a second plane of incidence toward a second position on the object, wherein the angle between the first plane of incidence and the second plane of incidence is at an angle that is not one of substantially zero degrees, substantially 45 degrees and substantially 135 degrees;    detecting a first scattered light intensity, wherein the first scattered light intensity comprises light intensity scattered from the first position;    detecting a second scattered light intensity, wherein the second scattered light intensity comprises light intensity scattered from the second position;    comparing the first scattered light intensity and the second scattered light intensity to determine a first aspect ratio of a defect on the surface of the object.