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:
Jul. 05, 1994
Filed:
Mar. 05, 1992
Yong Liu, Berkeley, CA (US);
Avideh Zakhor, Berkeley, CA (US);
Andrew Neureuther, Berkeley, CA (US);
Regents of the University of California, Oakland, CA (US);
Abstract
A method for making a mask for optical lithography or other projection printing, wherein the mask is represented by a mask pattern, is disclosed herein. The mask provides a substantially binary output image on the surface of a wafer as light is applied to the mask. Light passes through the mask and onto a wafer at varying intensities, such intensities represented by output intensity values, the threshold values of which produce output images within predetermined constraints. The method includes the steps of defining sampling points which are representative of the binary output image. These sampling points are used in defining local objective functions, which are combined to give a total objective function. The present invention further includes the steps of adjusting the mask pattern to provide for minimization by optimization of the objective function, transferring the mask pattern to a mask generating machine to generate a mask, and generating a mask. Moreover, the present invention includes the step of providing an output image which is focused on a plurality of optical planes. Furthermore, the present invention includes the step isolating three of the plurality of optical planes so that their output intensity is optimized at these planes, thereby producing a focusing plane shift at the center focal plane as well as producing an extended depth of focus.