Patent ID: 7773212

Claim:
A system to analyze a surface of a substrate, comprising: a chuck for receiving the substrate, a motor for rotating the chuck around a central axis of the chuck at a rotational speed, a surface inspection assembly having, a first targeting assembly to direct a first light beam onto the surface of the substrate, the first light beam reflecting from the surface and thereby creating a first scattered light beam, a first collecting assembly to collect at least some of the first scattered light beam, and a first detector assembly coupled to the first collecting assembly to generate a first signal from the first scattered light beam, an edge detection assembly having, a second targeting assembly to direct a second light beam across an edge of the substrate, the edge of the substrate passing a portion of the second light beam, and reflecting a portion of the second light beam and thereby creating a second scattered light beam, where the second light beam is directed contemporaneously with the first light beam, and a throughbeam detector to collect the passed portion of the second light beam and to generate a third signal from the passed portion of the second light beam, wherein the third signal indicates a degree of alignment between a center of the substrate and the central axis of the chuck as it rotates, and a data processing module to receive the first signal and the third signal and to analyze the surface of the substrate using the first signal when the third signal indicates a sufficient degree of alignment between the rotating substrate and chuck wherein a single light source creates both the first light beam and the second light beam, and the first light beam and the second light beam have different wavelengths to each other.