Theory and Computer Simulation of Grain-Boundary and Void Dynamics in Polycrystalline Conductors

Abstract

AbstractMicrostructure evolution in polycrystalline metallic thin films under stress and electric current underlies many reliability issues in microelectronics. This paper presents a quantitative analysis of grain-boundary and void dynamics based on the coupling between bulk and interfacial mass transport phenomena with elastic deformations and current stressing. The formation and growth of intergranular voids in bamboo-structure conductor lines due to stresses that develop during processing is analyzed. The analysis is aided by self-consistent simulation of bulk and grain-boundary diffusional processes using bicrystal models with elastic grains. A systematic analysis is presented of the morphological evolution of transgranular voids in aluminum lines under current densities that are typical of electromigration testing. The effects of the electric field and surface properties on the morphological stability of voids are examined and morphologies that bifurcate from rounded or wedge-like void shapes are predicted. The theoretical results are discussed in the context of experimental data for void propagation under electromigration conditions.