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:
Aug. 10, 1999
Filed:
Dec. 03, 1997
Ayako Sugaya, Kawasaki, JP;
Nikon Corporation, Tokyo, JP;
Abstract
Position detectors are disclosed for reliable, high-accuracy detection of alignment marks on a wafer, including alignment marks consisting of small phase steps. The position detector comprises a phase plate located conjugate to an aperture stop. The phase plate produces a phase shift between the undiffracted light flux from the alignment marks and the diffracted light flux and a phase-contrast image is of the alignment marks is formed. The phase plate is switchable or insertable so that a bright-field image is also obtainable. Bright-field images and phase-contrast images are directly viewable or are received by one or more image sensor. A signal processor receives image signals from the image sensors and determines the position of the alignment marks. The sensor then provides a position signal that is used to move the wafer and reticle into alignment.