Al3Sc thin films for advanced interconnect applications

Al_xSc_1-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 °C, followed by recrystallization at 440 °C. After annealing at 500 °C, 24 nm thick stoichiometric Al₃Sc showed a resistivity of 12.6 μΩcm, 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.