EFFECT OF INTERCONNECT LINEWIDTH ON THE EVOLUTION OF INTRAGRANULAR MICROCRACKS DUE TO SURFACE DIFFUSION IN A GRADIENT STRESS FIELD AND AN ELECTRIC FIELD

摘要

Based on the weak formulation for combined surface diffusion and evaporation/condensation, we derive the governing equation of the finite-element induced both by stressmigration and electromigration. The corresponding program is developed for simulating the evolution of the intragranular microcracks caused by surface diffusion in copper interconnect lines under a gradient stress field and an electric field. ull Unlike previously published works, this paper is focused on how the interconnect linewidth influences the microcrack evolution. Numerical analysis results show that there exists a critical value of the linewidth $hat h_c$. When $hat h&hat h_c$, the microcrack will drift along the direction of the electric field by a stable form. When $hat hlehat h_c$, it will split into two small microcracks and the decrease of the linewidth is beneficial for the microcrack splitting. Besides, the critical linewidth increases with the increase of the electric field and the aspect ratio, and the critical linewidth first increases and then decreases with the increase of the stress gradient. That is, the increase of the electric field and the aspect ratio is beneficial for the microcrack to split. In addition, all of the critical values of the electric field, the aspect ratio and the stress gradient decrease with the decrease of the linewidth. The microcrack has a stronger dependence on the linewidth when $hat h&25$.