Reactive sputter deposition of zirconium nitride/aluminum nitride multilayers: Chemical competition effects and structural characterizations

We have examined in detail the process of reactive sputtering of elemental Zr and Al targets simultaneously in an argon/nitrogen mixture. The total pressure and optical emission from both target plasma discharges have been monitored as a function of increasing nitrogen fraction. We compare this situation with the usual case of single target operation and demonstrate the existence of a chemical competition effect between the individual target plasma discharges, which manifests itself in preferential reaction of nitrogen with Zr and sequential nitriding of Zr and Al targets with increasing nitrogen fraction. We have further examined the structure and composition of single layer zirconium nitride and aluminum nitride films, deposited at different nitrogen fractions, by symmetrical and glancing angle x-ray diffraction, and by electron probe microanalysis, and our results corroborate the existence of chemical competition effects. We demonstrate the possibility of synthesizing zirconium nitride/aluminum nitride multilayered thin films with each individual component layer close to being stoichiometric, and we show the presence of sharp composition modulation and ordered interfaces in such multilayers.