Multi-spot illumination for improved detection sensitivity

摘要

Methods and systems for minimizing interference among multiple illumination beams generated from a non-uniform illumination source to provide an effectively uniform illumination profile over the field of view of an inspection system are presented. In some examples, a pulsed beam of light is split into multiple illumination beams such that each of the beams are temporally separated at the surface of the specimen under inspection. In some examples, multiple illumination beams generated from a non-uniform illumination source are projected onto spatially separated areas on the surface of the specimen. A point object of interest illuminated by each area is imaged onto the surface of a time-delay integration (TDI) detector. The images are integrated such that the relative position of the illumination areas along the direction of motion of the point object of interest has no impact on the illumination efficiency distribution over the field of view.

主权项

1. An inspection system comprising:
a pulsed laser illumination source configured to generate a beam of illumination light; an optical subsystem that receives the beam of illumination light and splits the beam of illumination light into two or more secondary beams of illumination light, wherein the optical subsystem introduces a temporal delay among the two or more secondary beams of illumination light as the two or more secondary beams illuminate a surface of a specimen under inspection; and a detector operable to receive a first amount of light collected from the surface of the specimen illuminated by a first of the two or more secondary beams of illumination light, receive a second amount of light collected from the surface of the specimen illuminated by a second of the two or more secondary beams of illumination light, and generate an output value based on an integration of the first and second amounts of light for a period of time that exceeds a sum of a pulse duration of the beam of illumination light and the temporal delay.