| 摘要 |
An optical system for detection of anomalies, such as particles or pattern defects, on a surface (40) comprising:
optics (22,26,34,36) arranged to provide a beam (38) of radiation illuminating the surface at an oblique angle;
at least two detectors (110a,110b,111a,111b);
at least two optical elements (110a,110b,111a,111b) arranged to collect radiation scattered from the surface, each optical element arranged to direct the collected, scattered radiation to a corresponding one of the detectors, causing the detectors to provide output signals in response thereto, wherein the optical elements are located such that each of the detectors senses radiation scattered from the surface in a different direction;
a device comprising a moving stage (124) that causes relative motion between the beam and the surface; and
a processor (200) processing information from said detector output signals concerning radiation scattered from different parts of the surface in different directions from the detectors, and arranged to identify anomalies;
said device further comprising an acousto-optic deflector (30), such that each of the moving stage and the acousto-optic deflector causes relative motion between the beam and the surface so that the beam scans a scan path covering substantially the entire surface, said path including a plurality of arrays of scan path segments (50,50',50",50"'), wherein at least some of such scan path segments have a span shorter than the dimensions of the surface (40), and so that the beam is caused to illuminate different parts of the surface and so that the detectors provide output signals in response to radiation from different parts of the surface illuminated by the beam. |
