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:
Nov. 09, 1999
Filed:
Apr. 07, 1998
Carl Oppenheimer, Kingston, NH (US);
Mark Quaratiello, Medford, MA (US);
Robert J Bond, Newark, CA (US);
Lam Research Corporation, Fremont, CA (US);
Abstract
The center of a semiconductor wafer relative to a rotation axis of a spindle carrying the wafer is detected by turning the spindle while a line source of optical radiation is directed at the wafer. A CCD linear optical detector array extending along a line between the spindle axis to a point beyond the wafer periphery effectively detects the amount of optical energy intercepted by the wafer. The source is turned on for a predetermined duration and the detector is read out in response to a shaft encoder detecting that the spindle has moved to each of many predetermined angles. A microprocessor responsive to the optical detector determines the length of the line each time the detector turns on by deriving an indication of the amount of optical energy accumulated by the CCD array each time the detector turns on. The microprocessor combines the determined line length indications to detect the workpiece center relative to the spindle axis.