Evaluation of single- and multilayered amorphous tantalum nitride thin films as diffusion barriers in copper metallization

This study evaluates 40-nm-thick amorphous Ta2N (n-Ta2N) thin films with va rious compositions and metallurgical designs as diffusion barriers for copp er metallization, Results based on sheet resistance measurements, x-ray dif fraction analyses, and transmission and scanning electron microscopies cons istently follow a sequence of coarsening copper grains, transforming a-Ta2N into a crystalline phase, and finally forming {111}-faceted pyramid Cu3Si precipitates and TaSi2. The degradation of the single-layered stoichiometri c Ta2N (a-Ta67N33) barriers is primarily triggered by a premature crystalli zation of the amorphous barrier layers at temperatures as low as 450 degree s C. However, as adequately designed double-layered (20 nm Ta67N33/20 nm Ta 62N38) amorphous barriers can be subjected to high-temperature annealing wi thout crystallization, the effectiveness of the double-layered barriers can be significantly improved, elevating the degradation temperature by approx imately 100 degrees C. (C) 2000 American Vacuum Society. [S0734-2101(00)046 02-9].