The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 31, 1994
Filed:
Dec. 31, 1991
Charly D Allemand, Nantucket, MA (US);
Inspex, Inc., Billerica, MA (US);
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.