Electroless plating of low-resistivity Cu–Mn alloy thin films with self-forming capacity and enhanced thermal stability

Abstract

Previous studies have typically used sputter deposition to fabricate Cu–Mn alloy thin films with concentrated solute additions which have exceeded several atomic percentages, and the electrical resistivity values of the resultant films from previous studies are relatively high, ranging from 2.5 to 3.5μΩ-cm. Herein, we proposed a different approach by using electroless process to plate dilute Cu–Mn (0.1at.%) alloy thin films on dielectric layers (SiO2). Upon forming-gas annealing, the Mn incorporated into Cu–Mn films was segregated toward the SiO2 side, eventually converting itself into a few atomic layer thickness at the Cu/SiO2 interface, and forming films with a low level of resistivity the same as that of pure Cu films (2.0μΩ-cm). The interfacial layer served as not only a diffusion barrier, but also an adhesion promoter that prevented the film’s agglomeration during annealing at elevated temperatures. The mechanism for the dual-function performance by the Mn addition was elucidated by interfacial bonding analysis, as well as dynamic (adhesive strength) and thermodynamic (surface-tension) measurements.