Technologies enabling 3D stacking of MEMS

Abstract

In order to realize reliable 3D stacking of micro electromechanical systems (MEMS), interconnection and through wafer via technologies have been adapted from other areas and verified for MEMS applications. True stacking of a system including MEMS requires vias through the MEMS and electrical and mechanical interconnection to other devices like signal conditioning units and communication- and power devices. MEMS will typically have specific requirements regarding mechanical issues like stiffness, robustness, volume, and mass. The mechanical issues limit the range of applicable technologies. In this work three interconnection technologies have been selected, evaluated, and compared: Au stud bump bonding, SnAg micro bumps, and the SLID (solid liquid interdiffusion) technology using Sn and Cu. One via technology has been considered, namely hollow vias, which has been improved and tested in this work