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:
Feb. 27, 2018
Filed:
Dec. 15, 2015
Asml Holding N.v., Veldhoven, NL;
Yevgeniy Konstantinovich Shmarev, Lagrangeville, NY (US);
Stanislav Smirnov, Danbury, CT (US);
ASML Holding N.V., Veldhoven, NL;
Abstract
An inspection apparatus may determine precise OV measurements of a target on a substrate using an optical pupil symmetrizer to reduce the inspection apparatus's sensitivity to asymmetry and non-uniformity of the illumination beam in the pupil plane. The inspection apparatus includes an illumination system that forms a symmetrical illumination pupil by (1) splitting an illumination beam into sub-beams, (2) directing the sub-beams along different optical branches, (3) inverting or rotating at least one of the sub-beams in two dimensions, and recombining the sub-beams along the illumination path to symmetrize the intensity distribution. The illumination system is further configured such that the first and second sub-beams have an optical path difference that is greater than a temporal coherence length of the at least one beam and less than a depth of focus in the pupil plane of the objective optical system.