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:
Jan. 09, 1996
Filed:
Sep. 06, 1994
J Casey Donaher, Westford, MA (US);
David S Holbrook, Woburn, MA (US);
Shepard D Johnson, Arlington, MA (US);
James A Sozanski, Littleton, MA (US);
MRS Technology, Inc., Chelmsford, MA (US);
Abstract
A system for aligning substrates when preparing flat panel displays by lithography. A spherical reflector (imaging mirror) is used to focus a small geometric object, such as a cross, etched at the center of the reflector. The cross is projected toward a beam splitter and is then reflected onto the mirror which, in turn, images it on the surface of the substrate being used in the lithographic process. This optical system, which has a numerical aperture of about 0.05 radians, provides maximum depth of field with essentially no aberrations, and produces a relatively large probe image on a large alignment mark. The surface of the substrate carries a grid of stepped patterns as an alignment mark. The steps diffract the light received, and the diffracted light passes through a lens system to a sensor associated with the lens system. The amount of light diffracted is dependent upon where the image strikes the steps in the grid. Thus, a correlation between position and the amount of light received by the sensor exists, and, so, the substrate can be precisely aligned.