Particle detection on patterned wafers and the like
Patent 4898471 Issued on February 6, 1990. Estimated Expiration Date: 
September 19, 2008. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
September 19, 2008. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3909602 Automatic detector for microscopic dust on large-area, optically unpolished surfaces Foreign substance inspecting apparatus Photomask inspection apparatus and method with improved defect detection Automatic contaminants detection apparatus Foreign particle detecting method and apparatus Patent #: 4669875 InventorsAssigneeApplicationNo. 248309 filed on 09/19/1988US Classes:356/394, With comparison to master, desired shape, or reference voltage356/237.4, On patterned or topographical surface (e.g., wafer, mask, circuit board)356/338, With photocell detection356/398With object being compared and light beam moved relative to each other (e.g., scanning)ExaminersPrimary: Rosenberger, Richard A.Attorney, Agent or FirmForeign Patent References
International ClassG01B 011/00AbstractA particle detection on a periodic patterned surface is achieved in a method and apparatus using a single light beam scanning at a shallow angle over the surface. The surface contains a plurality of identical die with streets between die. The beam scans parallel to a street direction, while a light collection system collects light scattered from the surface with a constant solid angle. The position of the collection system as well as the polarization of the light beam and collected scattered light may be arranged to maximize the particle signal compared to the pattern signal. A detector produces an electrical signal corresponding to the intensity of scattered light that is colelcted. A processor constructs templates from the electrical signal corresponding to individual die and compares the templates to identify particles. A reference template is constantly updated so that comparisons are between adjacent die. In one embodiment, the templates are made up of registered positions where the signal crosses a threshold, and the comparison is between corresponding positions to eliminate periodic pattern features, leaving only positions representing particles.Other References
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