DIELECTRIC BARRIERS FOR CU METALLIZATION SYSTEMS

The barrier properties of PECVD silicon oxynitride films in contact wi th copper were investigated with respect to the utilization of these f ilms in copper based metallization systems, Therefore, different analy tical and electrical methods were employed to study the interaction of SiOxNy with copper. No copper diffusion in the films investigated was observed after applying a thermal stress of 450 degrees C. However, c opper migration was detected after applying thermal and electrical str ess simultaneously (BTS). C-V and I-V measurements before and after di fferent BTS-conditions were performed on MIS-structures with copper do ts. The shift of the C-V curves due to copper migration decreases with increasing N/O-ratio of SiOxNy films, demonstrating the better barrie r properties of silicon nitride compared to silicon oxide. Additionall y, the time to failure (TTF) was studied as a function of thermal and electrical stresses. Again, SiNx-samples achieved the highest TTF-valu es. The polarity dependence of the leakage current suggests a Cu ion d rift transport mechanism.