Fluoride antireflection coatings for deep ultraviolet optics deposited by ion-beam sputtering

Abstract

Optically high quality coatings of fluoride materials are required in deep ultraviolet (DUV) lithography. We have applied ion-beam sputtering (IBS) to obtain fluoride films with smooth surfaces. The extinction coefficients were of the order of 10(-4) at the wavelength of 193 nm due to the reduction of their absorption loss. The transmittance of the MgF2/GdF3 antireflection coating was as high as 99.7% at the wavelength of 193 nm. The surfaces of the IBS deposited films were so smooth that the surface roughness of the A1F3/GdF3 film was comparable with that of the CaF2 substrate. The MgF2/GdF3 coating fulfilled the temperature and humidity requirements of military specification. Thus, the IBS deposited fluoride films are promising candidate for use in the DUV lithography optics.

Reflectance and transmittance model for multilayer optical coatings with roughness at oblique incidence

“…However, actually any thin film has certain surface roughness. In some applications, this roughness has a very important influence on its optical characteristics, such as deep-ultraviolet sculpture [1], ring lasers [2], gravitational wave detectors [3], etc. Therefore, it is important to establish a theoretical analysis model of multilayer optical characteristics when considering surface roughness.…”

Influence of substrate temperatures on the properties of GdF_3 thin films with quarter-wave thickness in the ultraviolet region

“…Among the very limited number of materials, besides LaF 3 , GdF 3 is a potential high refractive index candidate for further development in the excimer laser application area. Furthermore, these fluoride materials have the potential for application in the UV region down to 130 nm [3,6]. It was shown that the least amount of optical loss of the fluoride can be obtained by resistive heating evaporation.…”

Antireflective structures fabricated from silica nanoparticles with regular arrangement

“…Because the lowest refractive indices for dielectrics are above 1.35, bulk materials cannot attain this value. Therefore, many effective approaches based on gratings [1], etching or leaching of glass [2,3], sol-gel synthesis [4], sputtering [5], phase separation and selective dissolution [6], and dip coating of particles [7] are proposed to achieve low-index materials. However, to realize broadband antireflection, multilayer coatings with different index should be used for reducing reflection of different wavelength [8].…”