(Invited) Al-Al Waferbonding Process Development for Heterogeneous Integration

Abstract

This paper presents a surface-activated Al-Al wafer bonding process for patterned 200 mm wafers that removes the native oxide in an argon plasma and enables high bond quality with accurate alignment at temperatures below 300 °C. The study focuses on various factors that influence the final Al-Al bond in terms of contact resistance and shear strength. In addition to temperature, force and time during the actual bonding process, these include steps during the wafer fabrication that affect the Al bonding pads and the wafer bow. Furthermore, the impact of a post-bond cleaning process on the final bond result is analyzed. This work shows a low temperature Al-Al bonding process with high yield >90%, excellent bond strength >150 MPa and contact resistances in the mΩ range.