Experimental demonstration of evanescent-coupled antireflection coatings

Evanescent-coupled antireflection coatings (EC-ARCs) are a form of ARC designed to operate in the hypernumerical aperture regime relying on evanescently coupled resonators to provide backward going fields for destructive interference. Two experimental EC-ARC designs are tested in an immersion interference lithography system at a wavelength of 405 nm: a MgF2 vertical bar Cr surface state resonator based ARC at a numerical aperture (NA) of 1.4046 and transverse magnetic polarization, and a SiO2 vertical bar HfO2 vertical bar Si dielectric resonator based ARC at an NA of 1.5 and transverse electric polarization. The MgF2 vertical bar Cr system was shown to partially suppress standing waves with a void footing indicating the system is resonating, albeit in a suboptimal fashion. The SiO2 vertical bar HfO2 vertical bar Si system was shown to almost fully suppress standing waves. These results indicate that with improved manufacturing techniques evanescent-coupled ARCs can be an effective method of standing wave suppression for photolithography. Published by the AVS.