Dual Ion Beam Sputtering of Carbides for EUV Reflectance

There is a need for thin optical coatings that can be produced at low temperatures and have a high reflectance at the extreme ultraviolet (EUV), λ < 1200 A. Currently, the best such materials are silicon carbide (SiC) and boron carbide sputtered onto optical surfaces. The EUV reflectance of sputtered SiC, however, is not as high as that of the sputtered target materials (sintered or CVD -SiC). More significantly, the reflectance of both sputtered films degrades with time. In previous work the reflectance degradation of the SiC films has been quantified, and efforts to ameliorate it via ion-beam assisted deposition (BAD) were described. Further work on sputtered SiC films is reported, including chemical and structural analysis. In addition, the degradation behavior of sputtered boron carbide is discussed.