Simulation and Optimization of 3D Heterogeneous Integration of Inertial Micro-System

This paper presents a new 3D heterogeneous integration scheme for inertial Micro-system, where a TSV interposer with a cavity is used to separate two aligned TSV interposers that are mounted with inertial MEMS (Micro Electro-Mechanical System) devices, ASIC (Application Specific Integrated Circuit) chips, and passive components receptively. A finite element simulation method that uses equivalent elements and sub-model methods is developed to do design for reliability in Thermal Cycling Test (TCT). Comparing with the normal simulation method, an agreement is obtained in the stress distribution in the MEMS chips, TSVs and micro bumps. In the meantime, the simplified simulation method provides a competitive accuracy, the difference is 0.88% in the maximum deformation of the whole model between the two methods, the difference is 0.41% in the maximum deformation of the TSV and 0.65% in the micro bump at the most dangerous position. Base on this simplified simulation method, a 3D heterogeneous inertial micro-system is analyzed and optimized. The design of ladder TSV with the usage of underfill and gold balls is selected. The simulation results also showed that RDL (Redistribution Layer) can make significant influence on the stress distribution in the systems. If considering RDL, the maximum stress inside the micro bump at the most dangerous location increases by 62.79% while the max stress in TSV decreases by 14.03%, which means that stress optimization should also be carried out after designing the RDL layout.