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:
Jun. 11, 2019
Filed:
Jan. 16, 2017
Asml Netherlands B.v., Veldhoven, NL;
Simon Reinald Huisman, Eindhoven, NL;
Alessandro Polo, Arendonk, BE;
Duygu Akbulut, Eindhoven, NL;
Sebastianus Adrianus Goorden, Eindhoven, NL;
Arie Jeffrey Den Boef, Waalre, NL;
ASML NETHERLANDS B.V., Veldhoven, NL;
Abstract
In an alignment sensor of a lithographic apparatus, position sensing radiation is delivered to a target (P). After reflection or diffraction from the target, position sensing radiation is processed to determine a position of the target. Reference radiation interferes with the position sensing radiation) while a relative phase modulation is applied between the reference radiation and the position sensing radiation. The interfering radiation includes a time-varying component defined by the applied phase modulation. The interfering radiation is delivered to two photodetectors in such a way that each photodetector receives said time-varying component in anti-phase to that received at the other photodetector. A difference signal (i(t)) from said photodetectors contains an amplified, low noise version of said time-varying component. This is used in determining the position of the target. Mode matching enhances interference. Surface scattered radiation is rejected.