Direct index of refraction measurement of silicon and ruthenium at EUV wavelengths

The use of coherent radiation from undulator beamlines has been used to directly measure the real and imaginary parts of the index of refraction of several metals'. Here we extend the same interferometric technique to slightly higher energies, and measure the indices of refraction of silicon and ruthenium, essential materials for extreme ultraviolet (EUV) lithography. Both materials are tested at-wavelength (13.4 nm.) Silicon is also measured about its L-2 (99.8 eV) and L-3 (99.2 eV) absorption edges. This measurement technique is currently being expanded further to soft X-ray wavelengths.