Al${}_3$Sc thin films for advanced interconnect applications

Al${}_x$Sc${}_{1-x}$ thin films have been studied with compositions around Al${}_3$Sc ($x$ = 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 Al${}_3$Sc showed a resistivity of 12.6 $\mu \mathrm{\Omega }$cm, 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 Al${}_3$Sc, these results indicate that Al${}_3$Sc 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.