Optical inspector with selective scattered radiation blocker

摘要

An optical inspector includes a radiating source, a time varying beam reflector, a telecentric scan lens, a blocker, a focusing lens, an aperture, and a detector. The radiating source irradiates a first position of on the time varying beam reflector with a source beam. The time varying beam reflector directs the source beam to the telecentric scan lens, which in turn directs the source beam to a transparent sample. A portion of the source beam travels through the transparent sample to another surface. The blocker blocks scattered radiation originating at the other surface. Scattered radiation originating from the transparent sample is not redirected by the blocker and is focused by the focusing lens to a first focal plane. The focused scattered radiation passes through the aperture before irradiating the detector. The detector output an intensity measurement of the scattered radiation that irradiates the detector.

主权项

1. An apparatus, comprising:
a time varying beam reflector; a radiating source that irradiates the time varying beam reflector; a waveplate that is positioned between the radiating source and the time varying beam reflector; a telecentric scan lens that directs the radiation reflected by the time varying beam reflector onto a transparent sample and a stage, wherein the radiation reflected by the time varying beam reflector and directed by the telecentric scan lens produces a moving irradiated spot on the transparent sample and the stage, wherein the irradiation of the sample causes scattered radiation and specular reflected radiation to reflect from the transparent sample, wherein the irradiation of the stage causes scattered radiation to reflect from the stage, and wherein the telecentric scan lens directs the specular reflected radiation to the time varying beam reflector; a focusing lens that receives scattered radiation from the transparent sample, wherein the focusing lens is orientated at an oblique angle to the plane of incidence of the moving irradiated spot on the transparent sample; a blocker that redirects scattered radiation from the stage away from the focusing lens while not blocking scattered radiation from the transparent sample, wherein the blocker is located between the focusing lens and the plane of incidence of the moving irradiated spot on the stage; and a detector located near the focal plane of the focusing lens.