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:
Jan. 13, 2004
Filed:
Aug. 17, 2001
Adam E. Norton, Palo Alto, CA (US);
Sensys Instruments Corporation, Santa Clara, CA (US);
Abstract
A notch or flat sensor for a semiconductor wafer on a wafer stage or support includes a dual photodiode detector arrangement located at the edge position of the wafer. Each photodiode element has substantially equal coverage of the wafer edge when the wafer's notch or flat is not proximate to the detector, but has different coverage from the other photodiode when the notch or flat is proximate to the detector. A light source illuminates the edge of the wafer opposite the detector arrangement. Comparison of the light intensity sensed by each photodiode, e.g. by means of a differential amplifier circuit and threshold sensor, reveals the position of the notch or flat.