Simulations of Wafer-to-Wafer Bonding Dynamics and Deformation Mechanisms

In this study, we present a parametric simulation environment based on 2-D axisymmetric finite-element modeling to study the deformation mechanisms and dynamics of wafer-to-wafer bonding. The developed model enables studying variations of bonding recipes and incoming wafer configurations. The interaction between wafers is modeled by the cohesive contact approach. The air pressure and diffusion at the bonding front are modeled through a novel approach based on spring implementation with calibrated stiffness and damping coefficients, reducing the simulation time significantly. The simulation results were compared to the experimental results obtained through the bonding of wafers with different incoming shapes and warpage levels (70 µm – 250 µm). The comparisons were made using two key metrics: misalignment and bond-wave propagation speed. Using the simulations, the mechanism of deformation and bonding dynamics are investigated and correlations between the incoming wafer shape and post-bonding misalignment/warpage are made. The configurations that reduce the post-bonding misalignment and warpage are proposed and verified using simulations.