Efforts to control the EUV reflectance degradation of sputtered SiC films

There is a need for thin optical coatings that can be produced at low temperatures and have a high reflectance in the extreme ultraviolet (EUV). Currently, the best such material is silicon carbide (SiC) sputtered onto optical surfaces from targets of beta-SiC which were produced by chemical vapor deposition (CVD). The EUV reflectance of these films, however, is not as high as that of polished CVD SiC, and in addition it degrades with time. In this study the nonreversible reflectance degradation is quantified, and efforts to ameliorate it via ion-assisted deposition (IAD) and other techniques are detailed.