Barrierless Cu-Ni-Mo Interconnect Films with High Thermal Stability Against Silicide Formation

Cu-Ni-Mo alloys were investigated to increase thermal stability against silicide formation. The alloy compositions were chosen such that an insoluble element (Mo) solute was dissolved into Cu via a third element Ni which is soluble in both Cu and Ni. Thin-film Cu-Ni-Mo alloys were prepared by magnetron sputtering. The films with Mo/Ni ratio of 1/12 exhibited low electrical resistivities in combination with high thermal stabilities against silicide formation, in support of a tentative "cluster-plus-glue-atom" model for stable solid solutions. In particular, a (Mo1/13Ni12/13)(0.3)Cu-99.7 sample reached a minimum resistivity of 2.6 mu Omega cm after 400A degrees C/1 h annealing and remained highly conductive with resistivities below 3 mu Omega cm even after 400A degrees C/40 h annealing. These alloys are promising candidates for future interconnect materials.