Growth, Thermal Stability and Cu Diffusivity of Reactively Sputtered NbN Thin Films as Diffusion Barriers between Cu and Si

摘要

NbN_x films were prepared by RF reactive magnetron sputtering from a Nb target in N_2/ Ar gas mixtures and then used as diffusion barriers between Cu and Si substrates. Material characteristics of the NbN_X films were investigated and were correlated with the N_2/Ar flow ratio. The variations in film resistivity is correlated with the change of phases and chemical compositions from α-Nb, β-Nb_2N, Y-Nb_4N_3, S-NbN + 8'-NbN as the N_2/Ar ratio is increased. The thermal stability of Cu (60 nm)/NbN_x (25 nm)/Si multilayers were investigated and our results indicated that the barrier performances were significantly affected by the chemical composition of NbN_x films. The diffusion coefficient of Cu in NbN_x was measured by four-point probe analysis after annealing Cu/NbN_x/Si multilayered samples in the temperature range of 600-850°C. Cu diffusion in NbN_x had components from the grain boundaries and the lattice. In addition, our results suggest that the NbN_x can be used as a potential diffusion barrier for Cu metallization as compared to the conventional TaN.