METHOD OF DETECTING AND CLASSIFYING SCRATCHES AND PARTICLES ON THIN FILM DISKS OR WAFERS

Scratches, pits and particles which are smaller or larger than the beam size may be measured and identified by single and multiple beam techniques. In one embodiment, the invention uses a pair of orthogonally oriented laser beams, one in the radial and one in the circumferential direction. In another embodiment, two pairs of orthogonally oriented laser beams are used. The scattered light from radial and circumferential beams allows the detection and classification of particles, pits and scratches. In other embodiments, single beam techniques are used to classify radial and circumferential defects.