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:
Mar. 02, 1993
Filed:
Sep. 05, 1991
Kazuhiro Yamashita, Amagasaki, JP;
Noboru Nomura, Kyoto, JP;
Matsushita Electric Industrial Co., Ltd., Osaka, JP;
Abstract
An optical apparatus for aligning a reticle and a wafer together in connection with reduction projection onto the wafer of an image of a circuit pattern formed on the reticle. Two light beams having slightly different frequencies are concurrently applied to alignment gratings on the reticle and alignment gratings on the wafer through the windows on the reticle and a reduction projection lens. Heterodyne signals of interference rays resulting from diffraction by the alignment gratings on the reticle of the light applied to the alignment gratings are caught by a first optical sensor. Heterodyne signals of interference rays resulting from diffraction by the alignment gratings on the wafer of the light applied to the alignment gratings are caught by a second optical sensor. The difference in phase of the heterodyne signals detected by the respective optical sensors is detected by a phase meter, and the position of the wafer relative to the reticle is adjusted so that the phase difference is reduced to zero.