Thermal-electric-mechanical simulation of a multilevel metallization system

In modern metallization systems mechanical stress due to CTE mismatch is one of the reliability problems. With the help of finite element simulations the thermal-electrical-mechanical behavior can be calculated. The use of a reference temperature for the stress free state in the simulations is insufficient to determine the stress field in the metallization. The intrinsic stress resulting from the processing is hereby not considered. The simulation of the process steps by the birth and die capability of ANSYS is time consuming and complex. A possibility to consider the intrinsic stress in the metallization system is the use of averaged CTEs from measurements of a multi-level stack depending on the horizontal running direction of the interconnect in the x- or y-direction, or in from literature. The values were taken for a comparison between calculated stress field of the stacked metallization system with process steps and the reference temperature for the stress free state. The achieved simulation results help for a better understanding of the stress behavior.