Copper-Silver Alloy for Advanced Barrierless Metallization

In this study we observed significantly improved properties, over a pure copper (Cu) film, for a copper-silver alloy film made with a pure copper film co-sputtered with a minute amount of either Ag_0.3N_0.4 or Ag_1.2N_0.7 on a barrierless Si substrate. In either case, no noticeable interaction between the film␣and the Si substrate was found after annealing at 600°C for 1 h. The Cu(Ag_0.3,N_0.4) film was thermally stable after annealing at 400°C for 240 h. The film’s resistivity was ∼2.2 μΩ cm after annealing at 600°C, while its leakage current was found to be lower than that of a pure Cu film by three orders of magnitude. The adhesion of the Cu(Ag_1.2,N_0.7) film to the Si substrate was approximately seven times that of a pure Cu film to a silicon substrate. Hence, a Cu film doped with Ag and N seems to be a better candidate for both barrierless metallization and the making of superior interconnects.