Method and apparatus for detecting particles on a surface of a s

Details Method and apparatus for detecting particles on a surface of a s Method and apparatus for detecting particles on a surface of a s

1995-02-09

1997-08-19

Font, Frank G.

Optics: measuring and testing

Inspection of flaws or impurities

Having predetermined light transmission regions

25055941, G01N 2100

Patent

active

056593902

ABSTRACT:
An apparatus for detecting particles on the front surface of a patterned 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 crossed polarizer with the Fourier diffraction pattern being used as both a read beam and a write beam for the spatial light modulator. A camera detects scattered light collected from the area by the lens and not blocked out by the Fourier mask.

REFERENCES:
patent: 4806774 (1989-02-01), Lin et al.
patent: 5046847 (1991-09-01), Nakata et al.
patent: 5090807 (1992-02-01), Tai
patent: 5276498 (1994-01-01), Galbraith et al.

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