Cu nanowire fine-pitch joints for next gen heterogeneous chiplet integration

Heterogeneous integration (HI) is a key driver in the field of advanced electronic packaging and depends on the compatibility of various integration technologies at the same hierarchy level. Enabling the cost-effective realization of multi-chiplet systems with a wide range of interconnect pitches the adoption of novel die level bonding technologies appears inevitable. The use of Cu nanowire (NW) based bumps is a promising approach for closing the gap between Cu/SiO2 hybrid bonding and solder based microbumps. Cu-NW joints can be formed under ambient conditions at temperatures below 250 degrees C. In this study, we investigated the realization of Cu-NW fine- pitch joints with a diameter of 10 mu m using NWs with diameter of 100 nm. Overall, the collected data show comprehensible correlations between the resulting shear strengths and microscopic shear failure mechanisms on one hand and the process parameters on the other. The shear test results of die-to-die (D2D) stacks bonded at a temperature of 220 degrees C reveal strengths above 70 MPa. The fully compatible back-end-of-line (BEOL) fabrication process on 300 mm wafer level, the short and resource-efficient bonding process in conjunction with the remarkable joint properties highlight the potential of the proposed technology.