Fluoride antireflection coatings for deep ultraviolet optics deposited by ion-beam sputtering.
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.
Central Research Laboratory, Japan Aviation Electronics, Ltd., 3-1-1 Musahino, Akishima-shi, Tokyo 196-8555. yoshidats@jae.co.jp
Toshiya
T
Yoshida
Keiji
K
Nishimoto
Keiichi
K
Sekine
Kazuyuki
K
Etoh