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:
Sep. 16, 2003
Filed:
Mar. 04, 2000
Joseph J. Danko, Shrewsbury, MA (US);
Inspex Incorporated, Billerica, MA (US);
Abstract
A method and apparatus for inspecting a surface of a semiconductor wafer having repetitive patterns for contaminant particles using scattered light by illuminating an area on the surface with two beams of light at different approach angles which are independent from each other and then imaging the area illuminated onto a camera positioned above the surface using an imaging lens. Each light beam striking the surface of the semiconductor wafer produces a Fourier diffraction pattern of light scattered from the surface in the back focal plane of the imaging lens. The two diffraction patterns are offset from each other if the two approach angles are not symmetrically disposed relative to an axis of the wafer. In setting up the apparatus, the angle of incidence of one of the beams is adjusted to shift one of the diffraction patterns, if necessary, so that it overlaps the other diffraction pattern. In this way, a spatial filter having masking bars sized and shaped to mask off the diffraction pattern from one beam will also mask off the diffraction pattern from the other beam. If the two approach angles are symmetrically disposed, then the two diffraction patterns overlap and adjustment of the angle of incidence of one of the beams is not necessary. The apparatus includes an arrangement for independently setting each one of the two approach angles and independently adjusting the angle of incidence of each light beam.