Masashi Numata

Thin and Low-Resistivity Tantalum Nitride Diffusion Barrier and Giant-Grain Copper Interconnects for Advanced ULSI Metallization

The barrier performance and properties (resistivity, crystalline phase and surface microroughness) of tantalum nitride films, as well as the relationship between grain size and diffusivity of copper films, are reported. The resistivity and Ra roughness of Ta2N film formed by reactive sputtering using argon and nitrogen plasma are ~200 µΩcm and ~0.35 nm, respectively. The Ta2N diffusion barrier exhibits better barrier performance than Ta4N and bcc-Ta diffusion barriers. Giant-grain copper interconnects formed by sputtering in low-energy ion bombardment process show lower diffusivity than small-grain copper interconnects. The barrier performance of tantalum nitride film was evaluated by electrical measurement. An n+p junctions having 20 µm×20 µm contact holes filled with 10-nm-thick Ta2N diffusion barriers and giant-grain copper interconnects exhibit no increase in reverse-bias current after annealing at 700°C for 30 min in argon ambient.