Atomistic insights into the gradient polycrystalline effects on interfacial behavior in Cu-Cu direct bonding using molecular dynamics simulation

JT Zhou and LY Shen and X Yang, MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING, 200, 109991 (2025).

DOI: 10.1016/j.mssp.2025.109991

Cu-Cu direct bonding is vital for advanced electronic packaging. However, achieving high bonding quality is challenging owing to the restricted self-diffusion rate of copper. This study introduces the opposite-gradient polycrystalline bonding method to further modify the bonding quality for the first time. Using molecular dynamics simulations, the gradient polycrystalline effects on the atomic diffusion and mechanical reliability were investigated. Results showed that the opposite-gradient polycrystalline Cu-Cu bonding (G-G) outperformed conventional uniform polycrystalline bonding in atomic diffusion and achieved fewer dislocations after bonding. G-G bonding reached highest mean square displacement (MSD) with peak value of around 20 & Aring;(2) and diffusion coefficients of 1.66 x 10(-12) m(2)/s. Moreover, higher temperature significantly promoted the atomic diffusion and G-G bonding exhibited acceptable thermal stability. The tensile properties of G-G bonding were superior due to closely arranged grain boundaries which enhanced the deformation resistance. This study provides a novel approach to achieving high-quality Cu-Cu bonding through the grain boundaries arrangement.

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