System with multiple scattered light collectors

摘要

A method for inspecting a surface of a workpiece for asymmetric defects, by scanning an incident beam on the surface of the workpiece to impinge thereon to create reflected light extending along a light channel axis in a front quartersphere and scattered light, the incident beam and the light channel axis defining an incident plane, collecting the scattered light at a plurality of collectors disposed above the surface at defined locations such that scatter from asymmetric defects is collectable by at least one collector, detecting collector output and generating signals in response, and processing the signals associated with each collector individually to obtain information about asymmetric defects.

主权项

1. A method for inspecting a surface of a workpiece for asymmetric defects, the method comprising:
scanning an incident beam on the surface of the workpiece to impinge thereon to create reflected light, extending along a light channel axis in a front quartersphere, and scattered light, the incident beam and the light channel axis defining an incident plane, collecting the scattered light at a plurality of collectors disposed above the surface at defined locations such that scatter from asymmetric defects is collectable by at least one collector, defining a channel by identifying a selected set of the collectors that have collected the scatter, obtaining signals associated with each collector in the channel, individually filtering the signals associated with each collector in the channel to obtain filtered output associated with each collector in the channel, individually thresholding the filtered signals to obtain thresholded filtered signals associated with each collector in the channel, combining individually thresholded filtered signals into a combined signal, and processing the combined signals to obtain information about asymmetric defects.