Study on copper-to-copper bonding of three-dimensional integrated circuits using the quasicontinuum method

Cu-Cu bonding presents an attractive approach to bottom-up manufacturing, facilitating nanoparticle production, linking, and restoration. The ramifications of varying bonding depths and orientations exhibit distinct characteristics. At the same time, investigations into the material composition of nanoscale bonded pairs involve scrutiny of atomic slippage, strain distribution, and the force-displacement profile. The methodology simulates the Cu-Cu bonding process by implementing the quasi-continuum (QC) approach, constituting a multifaceted mixed molecular dynamics technique integrating atomistic and continuum methods. The analysis of results reveals variations in the Contact effect induced by the four orientations, along with discrepancies in the atomic slippage observed in distinct directions. Notably, a pronounced distinction is discernible in the directional movement. Specifically, the strained regions on the flat surface of the lower substrate, characterized by the directionality of X[001]-Y[110], exhibit a notably broader range of atomic slip compared to regions strained by alternative orientations. Furthermore, the directional alignment of X[110]-Y[111] illustrates that irrespective of whether the lower substrate's surface is flat or rough, the orientation of atomic slip diverges. In conclusion, our study employed a quasi-continuous method to explore the bonding efficacy of copper-to-copper interfaces on flat and irregular substrate surfaces. Through this approach, we scrutinized the distributions of strain, stress, average Newtonian force, and atom differential arrangement direction across different orientations.