Dielectric barriers for Cu metallization systems

The barrier properties of PECVD silicon oxynitride films in contact with copper were investigated with respect to the utilization of these films in copper based metallization systems, Therefore, different analytical and electrical methods were employed to study the interaction of SiO(x)N(y) with copper. No copper diffusion in the films investigated was observed after applying a thermal stress of 450 degrees C. However, copper migration was detected after applying thermal and electrical stress simultaneously (BTS). C-V and I-V measurements before and after different BTS-conditions were performed on MIS-structures with copper dots. The shift of the C-V curves due to copper migration decreases with increasing N/O-ratio of SiO(x)N(y) films, demonstrating the better barrier properties of silicon nitride compared to silicon oxide. Additionally, the time to failure (TTF) was studied as a function of thermal and electrical stresses. Again, SiN(x)-samples achieved the highest TTF-values. The polarity dependence of the leakage current suggests a Cu ion drift transport mechanism.