Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1991-12-31
1994-05-31
Rosenberger, Richard A.
Optics: measuring and testing
By particle light scattering
With photocell detection
356237, 356239, 356431, 250572, G01N 2188
Patent
active
053173805
ABSTRACT:
A method and apparatus for detecting particles on a surface of an object, such as a virgin or patterned semiconductor wafer, ceramic tile, or the like. In one embodiment, an apparatus is provided in which a scanning beam of laser light is brought to focus as an arcuate scan line on a surface of the object at a grazing angle of incidence using an off-axis hypertelecentric mirror. A pair of light detectors are positioned at a meridional angle of about 30 degrees and at an azimuthal angle of about 4 degrees to measure forward scattered light from the surface. The object is then moved translationally so that the beam can scan another line of the surface. A light trap is provided to trap light that is reflected by the surface, and a series of masks are provided to mask light which is scattered by the hypertelecentric mirror and, in the case of patterned objects, light which is diffracted by the pattern imprinted on the object.
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Inspex Inc.
Pham Hoa Q.
Rosenberger Richard A.
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