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 AlF3/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.
- Publication:
-
Applied Optics
- Pub Date:
- March 2006
- DOI:
- 10.1364/AO.45.001375
- Bibcode:
- 2006ApOpt..45.1375Y
- Keywords:
-
- Optical materials;
- Coatings;
- Thin films;
- optical properties