Laterally graded periodic Mo/B₄C multilayer for extreme ultraviolet wavelength of 6.8-11.0 nm

Laterally graded periodic Mo/B₄C₆₀ multilayer mirrors for an EUV interval of 6.8-11.0 nm were deposited by direct current magnetron sputtering on silicon substrate. The structure properties and performance of laterally graded Mo/B₄C₆₀ multilayers were investigated by grazing X-ray reflectivity measurements and synchrotron radiation reflectance measurements. The results show that the multilayer period thickness D-spacing varies linearly from 4.39 nm to 7.82 nm in the long direction of the sample, indicating the average D-spacing gradient of 0.054 nm/mm. Reflectance of all measured point on the mirror is about 10% at the incident angle of 45°. Spectral width (FWHM) of the reflectance peaks varies from 0.13 nm to 0.31 nm with the increase of multilayer period thickness.