Al-Ge Eutectic Wafer Bonding and Bond Characterization for CMOS Compatible Wafer Packaging

Abstract

Most current MEMS packaging applications either use glass frit and anodic bonding or metals such as gold that are not compatible with CMOS front end processing. There is a growing need for a wafer bonding process that is suitable for both MEMS and CMOS fabs. Al-Ge based eutectic bonding not only overcomes most of the drawbacks associated with glass-frit and anodic bonding; it also provides a practical solution for wafer level packaging for CMOS/MEMS applications as both Al and Ge are CMOS and MEMS Fab-friendly materials. In addition to providing a hermetic seal, AlGe bonding provides an electrically conductive path between two substrates. This paper describes a practical AlGe based bonding and post bond characterization process. In addition, a novel post bond hermeticity/ leakage testing process is also described in this paper.