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. 25, 1997
Filed:
Sep. 20, 1995
Applicant:
Inventors:
Yukio Tokuda, Kawasaki, JP;
Yukio Takabayashi, Utsunomiya, JP;
Assignee:
Canon Kabushiki Kaisha, Tokyo, JP;
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
G03B / ;
U.S. Cl.
CPC ...
355 72 ; 355 53 ;
Abstract
A projection lens, a reticle stage and a light source optical system are supported by a cast frame above a wafer stage for holding a wafer thereon. A top portion of the cast frame has an enclosed hollow structure in which strengthening ribs are built, thereby substantially increasing the rigidity of the top portion. Since the ribs are built in the top portion of the cast frame, the surface area exposed to the wafer stage is reduced. As a result, there is little chance that the wafer is contaminated by any adherents to the cast frame.