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

摘要

There is a growing demand for MEMS wafer packaging processes where the CMOS wafer can be bonded to a MEMS wafer using CMOS foundry compatible materials. 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 (1). Glass frit bonding especially suffers from severe organic/ particles contamination from Pb (used to reduce bonding temp) and from organic binders (used in screen printing) in addition to having large seal width requirements in orders of lOOum. This justifies the need for a robust CMOS compatible metal based bonding process that not only provides a hermetic seal for smaller die sizes but can also provide electrical interconnections across the bond interface. The ability to make high-density and reliable electrical contacts between the MEMS and CMOS substrates can be very beneficial and opens the doors for a new generation of MEMS devices with added functionality smaller size, and lower cost per die.rnAlGe based eutectic bonding provides a practical solution for hermetic wafer level packaging due to the following unique features (a) Both Al and Ge are CMOS friendly (b) an electrically conductive path between two substrates (c) can be patterned easily and (d) allows for smaller die sizes. The Aluminum- Germanium system (2, 3) is a