Advanced Au-Au Direct Bonding for Enhanced Thermal Management in Heterogeneous Integration

Hybrid bonding emerges as a solution to meet the growing demand for high I/O density within 3D packaging, exhibiting promising heat dissipation capabilities. Heat transfer interface is the main bottleneck for heat dissipation in integrated circuit (IC) packages, and hybrid bonding is a promising solution. While challenges such as oxidation and surface flatness issues have been overcome in hybrid bonding technology for I/O applications, the significant disparity in scale between the heat transfer and the I/O interfaces exacerbates these challenges, limiting its application for heat dissipation, particularly with the mainstream Cu-SiO2 hybrid bonding method. This research advocates for using inert metals, notably gold, as a bonding layer to mitigate oxidation during the bonding process. Through this strategy, we have successfully realized bonding between chips of different materials at 300°C, 9 MPa and atmospheric conditions for 1 hour without using the chemical mechanical polishing (CMP) process. Analysis of EDS and SEM results shows a good bonding interface without oxidation. Additionally, the thermal conductivity of the bonding structure can reach about 100 W·m^-1·K^-1 under optimized conditions. Therefore, this study introduces a high-quality, high-thermal-conductivity Au-Au bonding strategy that eliminates the need for costly CMP process, demonstrating its potential in IC thermal management solutions and heterogeneous integration scenarios. Ultimately, this research aims to optimize the established Cu-SiO2 hybrid bonding process and broaden its applicability.