ASML Holding N.V.
Metrology tools comprising aplanatic objective singlet

Abstract:

A metrology tool, an aplanatic singlet lens, and a method of designing an aplanatic singlet lens are provided. The metrology tool is for determining a characteristic of a structure on a substrate. The metrology tool comprises an optical detection system for detecting radiation over a wavelength range. The optical detection system comprises an aplanatic singlet lens for focusing the radiation on to a detector. The aplanatic singlet lens has a n aplanatic wavelength which is within the wavelength range.