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:
Mar. 07, 2017
Filed:
Feb. 12, 2015
International Business Machines Corporation, Armonk, NY (US);
Timothy Allan Brunner, Ridgefield, CT (US);
Martin Burkhardt, White Plains, NY (US);
INTERNATIONAL BUSINESS MACHINES CORPORATION, Armonk, NY (US);
Abstract
This invention relates to a method of obtaining optimal focus for exposing a photoresist in an EUV lithography with an EUV mask containing a pattern with an assist feature. The invention also relates to an EUV mask with a special focus test target for monitoring focus in EUV lithography, and a method of fabricating this EUV mask by designing the special focus test target. The EUV mask contains a repeating pattern, wherein the repeating pattern has two different pitches, i.e. a first pitch and a second pitch, and contains an assist feature between main features. Because the two different pitches have different focus offsets, the difference between linewidths of said gratings provides a calibration curve which is a measure of focus. The method for monitoring focus is performing an EUV exposure using a focus position with a pre-determined focus position as calibrated using the linewidth difference between the two gratings. The EUV mask for monitoring focus of present invention is applicable to both test and product masks.