Optics: measuring and testing – Inspection of flaws or impurities – Having predetermined light transmission regions
Patent
1996-06-18
1998-09-08
Font, Frank G.
Optics: measuring and testing
Inspection of flaws or impurities
Having predetermined light transmission regions
356376, 25055941, G01N 2100
Patent
active
058052780
ABSTRACT:
An apparatus and method for detecting particles on a surface of a semiconductor wafer having repetitive patterns includes a laser for illuminating an area on the front surface at grazing angle of incidence with a beam of polarized light. A lens collects light scattered from the area and forms a Fourier diffraction pattern of the area illuminated. A Fourier mask blocks out light collected by the lens at locations in the Fourier diffraction pattern where the intensity is above a predetermined level indicative of background information and leaves in light at locations where the intensity is below the threshold level indicative of possible particle information. The Fourier mask includes an optically addressable spatial light modulator and a polarization discriminator. A camera detects scattered light collected from the area by the lens and not blocked out by the Fourier mask.
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Hamamatsu Photonics K.K., Hamamatsu Technical Data, Ferroelectric Liquid Crystal Spatial Light Modulator (FLC-SLM) model X4601, 4 pages.
Hamamatsu Photonics K.K., Hamamatsu Technical Data, Parallel Aligned Nematic Liquid Crystal Spatial Light Modulator (PAL-SLM) model X5641.
Font Frank G.
Inspex Inc.
Ratliff Reginald A.
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