Mitigation of wafer-to-wafer bonding distortions through accelerated simulations and measurements

Abstract

In this paper, an accelerated wafer-to-wafer bonding simulation approach, based on nonlinear spring implementation to represent the air resistance and diffusion at the bonding interface is employed. Using this approach, non-linear residuals of bonding overlay were investigated. Major events that lead to sudden changes and high scatter in residuals during bonding were identified and traced back to the bonding recipe applied and incoming wafer shapes. Mitigation strategies were formulated based on changes to the bonding recipe. Additionally, the impact of the bonding gap on the post-bonding distortions was investigated using a combination of measurements, mechanical and fluidic simulations. Finally, the simulations with pre-bonding bottom chuck bowing, as a scaling compensation strategy, were implemented and performed across different incoming shapes and bonding configurations. Simulation results were used to identify optimum bottom chuck bowing conditions, in an attempt to minimize experimental optimization efforts.