Grain boundaries-dominated migration failure of copper interconnect under multiphysics field: Insight from theoretical modeling and finite element analysis

Abstract

As the feature size of Cu interconnects in microelectronic devices are miniaturized into micro- and even nano-scale, the effects of grain boundaries (GBs) on the electromigration (EM) failure become more and more obvious. It is of fundamentally importance to investigate the grain boundaries dominated failure mechanism and lifetime of Cu interconnects. In this work, the interconnection models containing different grain boundaries were constructed by using finite element simulations. The simulation results indicate that the current density at Cu grain boundaries is lower, but the current will be increased locally, when it is almost perpendicular to grain boundaries. However, the temperature is higher locally at grain boundaries. In the early stage of atomic diffusion, thermal migration and stress migration also occur near grain boundaries, resulting in significant atomic segregation near grain boundaries, particularly at the intersection of grain boundaries and near the inclined grain boundaries with small angles to the current direction. The atomic diffusion is considerably accelerated as the density of grain boundaries is increased, but is slowed down by poorly connected columnar grain boundaries.