Interfacial Fracture Caused by Electromigration at Copper Interconnects

The present investigation delves into the failure model of cracking at the Cu/dielectric interface, specifically at the anode end of a copper interconnect that is triggered by electromigration. The study employs the continuous dislocation model to determine the stress field caused by interfacial mass diffusion that exists within and outside of the copper line. Apart from the anticipated tensile or compressive stress on the cathode or anode side, an anomalous stress singularity is identified at the interface between the dielectric layer and the anode end of the copper line. This singular stress distribution leads to cracking in the compressive portion of the dielectric layer at the anode end under the influence of electromigration. The theoretical predictions are in good agreement with experimental data, and a novel failure criterion akin to the stress intensity factor in fracture mechanics is formulated.