Cu1−xAlx films as alternatives to copper for advanced interconnect metallization

Abstract

CuxAl1−x thin films with 0.2 ≤ x ≤ 0.7 have been studied as potential alternatives for metallization of advanced interconnects. First-principles simulations were used to obtain the CuxAl1−x electronic structure and cohesive energy to benchmark different intermetallics and their prospects for interconnect metallization. Next, thin CuxAl1−x films were deposited by PVD with thicknesses in the range between 3 and 28 nm. The lowest resistivities of 9.5 μΩ cm were obtained for 28 nm thick stoichiometric CuAl and CuAl2 after 400 °C postdeposition annealing. Based on the experimental results, we discuss the main challenges for the studied aluminides from an interconnect point of view, namely, control of the film stoichiometry, the phase separation observed for off-stoichiometric CuAl and CuAl2, as well as the presence of a nonstoichiometric surface oxide.