Nanometer-designed Al/SiC periodic multilayers: characterization by a multi-technique approach

Nanometer-thick Al/SiC periodic multilayers, designed for the Extreme Ultra Violet (EUV) range, have been characterized by different techniques dedicated to such thin multilayers (each between 4 and 10 nm thick). In order to decrease the roughness and to improve the optical performances of the stacks, an ultrathin (2 nm) refractory metal layer has also been introduced, thus making Al/W/SiC and Al/Mo/SiC multilayer systems with three layers in period. The samples are deposited by magnetron sputtering. The stacks have a period ranging between 16 and 18 nm. Time-of-Flight SIMS (ToF-SIMS) is used here to determine the depth profiles of the different elements present within the multilayers. It is observed that the interfaces of the Al/W/SiC and Al/Mo/SiC multilayers are sharper than those of the Al/SiC system. X-ray emission spectroscopy (XES) is used to identify the chemical state of the Al and Si atoms within the multilayers and to check if there is any interfacial compound. The results show that there is no interaction between the Al and SiC layers leading to the formation of an interfacial compound. The results are confirmed by X-ray reflectivity (XRR) measurements. They show that the Al/SiC multilayers present large interfacial roughnesses, but the Al/W/SiC and Al/Mo/SiC multilayers have the lower roughness values. Copyright © 2010 John Wiley & Sons, Ltd.