Molecular dynamics simulation of Cu/Ta interface diffusion behavior under high temperature and high strain
Three-dimensional integration technology of using copper interconnects is an effective approach to enhance the performance of microelectronic devices.However,the diffusion of copper atoms into silicon can significantly degrade their performance of the electronic devices,which even can cause failure.Chemically stable tantalum(Ta)is often employed as a barrier layer to enhance reliability of the electronic devices.To study the diffusion behavior of at the Cu/Ta interface,molecular dynamics simulations were carried out to investigate the effects of temperature and strain coupling.The diffusion mechanism at the Cu/Ta interface was analyzed in both single-crystalline and polycrystalline structures.At elevated temperatures,Ta atoms can penetrate into the Cu crystal lattice after 10 ns of annealing,where the penetration depth is greater for polycrystalline Cu and can reach up to 1.5 nm.Upon strain application,multiple defects were generated in the polycrystalline Cu,including dislocation tangles,twinning,and grain boundary ruptures,which leads to increase of dislocation density in Ta and thicker diffusion layer of 3.3 nm.The molecular dynamics simulation results shows that Ta is a highly effective barrier layer under high temperature conditions.However,its resistance of Cu diffusion gradually decreases and even disappear under strain.This study provides valuable insights into the reliability of Ta as a diffusion barrier in Cu interconnects,contributing to the development of more robust microelectronic devices.
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