Silicon/silicon oxide and silicon/silicon nitride multilayers for XUV optical applications

Si/Si02 and Si/Si3N4 multilayers have been fabricated using a locally made reactive diode if-sputtering systern. 'Ihe layer alternation is obtained by modulating a partial pressure of oxygen or nitrogen near the sample using a silicon target and argon as sputtering gas. 02 and N2 partial pressure conditions were optimized to deposit stoechiornetric Si02 and Si3TV4 films without significant reaction with the silicon target. In-situ kinetic ellipsometry was used to monitore both thick film and multilayer deposition. 'I'he different interfaces appear very sharp with a little contamination of the silicon layers especially using oxygen. The multilayers were characterized by gazing X-ray reflection ( Cu - K line ), and the reflectivity was measured in the soft X-ray range (120 - 350 A ) by synchrolroii radiation. BotI1 Si/Si02 and SiIS13N4 multilayers exhibit well defmed Bragg peaks with very narrow bandpasses ( two to three times lower than the conventional M'/Si multilayer ),and high absolute reflectivities (up to 22% at 1 30 A ). The soft X-ray performances of these mirrors are explained using the physical characteristics deduced from kinetic ellipsometry, grazing X-ray reflection, infrared absorption and transmission electron microscopy measurements.