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:
May. 25, 1993
Filed:
Aug. 19, 1991
Applicant:
Inventors:
Assignee:
Hitachi, Ltd., Tokyo, JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
G01B / ;
U.S. Cl.
CPC ...
356401 ; 250548 ;
Abstract
A diffraction grating shaped reference pattern having the same grating pitch as diffraction grating shaped alignment pattern formed on a wafer is irradiated by alignment light, and the diffracted light signal obtained from the reference pattern is stored in a memory. The diffraction grating shaped alignment pattern formed on the wafer is irradiated by the alignment light, and the diffracted light signal from the alignment pattern is corrected based on the diffracted light signal stored in the memory.