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. 07, 1995
Filed:
Oct. 21, 1993
Takahiro Matsumoto, Atsugi, JP;
Noriyuki Nose, Atsugi, JP;
Kenji Saito, Atsugi, JP;
Koichi Sentoku, Kanagawa, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
A first Savart plate and an object to be measured are arranged on the light path of a Zeeman light source. The object to be measured is constructed of a diffraction grating on a mask and a diffraction grating on a wafer. A second Savart plate, a deflection plate and a photoelectric detector are sequentially arranged in the light path for the diffracted beams from the measured object. The output of the photoelectric detector is connected to a phase-difference unit to detect the phase difference between two beat signals. Herein, the light is split into two beams by the Savart plate. After a diffraction is caused by the diffraction gratings, thereafter, the beams are re-synthesized by the Savart plates. The two beams travel on the same light path, thereby improving a measurement accuracy.