Al3Sc Thin Films for Advanced Interconnect Applications

AlxSc1-x thin films have been studied with compositions around Al3Sc (x = 0.75) for potential interconnect metallization applications. As-deposited 25 nm thick films were x-ray amorphous but crystallized at 190 degrees C, followed by recrystallization at 440 degrees C. After annealing at 500 degrees C, 24 nm thick stoichiometric Al3Sc showed a resistivity of 12.6 mu Scm, limited by a combination of grain boundary and point defect (disorder) scattering. Together with ab initio calculations that found a mean free path of the charge carriers of 7 nm for stoichiometric Al3Sc, these results indicate that Al3Sc bears promise for future interconnect metallization schemes. Challenges remain in minimizing the formation of secondary phases as well as in the control of the non-stoichiometric surface oxidation and interfacial reactions with underlying dielectrics.