Evaluation of amorphous (Ta,W,Mo)-Si-N diffusion barriers between Cu and Si

This paper reports the investigation of sputtered Ta-Si-N, W-Si-N, and Mo-Si-N thin films as diffusion barriers for copper interconnects. The thermal stability of the barriers generally improves with increasing nitrogen concentration in the films, with the drawback of an increase in the film's resistivity. The stability reaches a peak value and then decreases with excessive amounts of nitrogen. This change of barrier property is attributed to the dependence of film's microstructure on the nitrogen content. Diode leakage current measurements indicate that Mo-Si-N has a lower resistivity and a higher thermal stability as compared to Ta-Si-N and W-Si-N.