Patent ID: 7623229

Claim:
A system configured to inspect a wafer, comprising: an illumination subsystem configured to direct light to a spot on the wafer at an oblique angle of incidence; a first detection subsystem configured to detect light scattered from one portion of the spot on the wafer and to generate output responsive to the detected light; a second detection subsystem configured to separately and simultaneously detect light scattered from different portions of the spot on the wafer and to separately generate different output responsive to the separately detected light, wherein the entire collection space of the second detection subsystem spans only a portion of azimuthal angles at which the first detection subsystem detects the scattered light, wherein the second detection subsystem comprises a first detector configured to separately and simultaneously detect the light scattered from the different portions of the spot and a second detector configured to separately and simultaneously detect the light scattered from the different portions of the spot, and wherein the first and second detectors are positioned such that there is a half pixel shift between the first and second detectors; and a computer subsystem configured to detect defects on the wafer using the output generated by the first detection subsystem and the different output separately generated by the second detection subsystem.