Interdiffusion mechanism and thermal conductance at the interfaces in Cu-to-Cu bonds achieved by coating nanolayers

Efficient heat dissipation is a critical consideration in the design of high-performance electronics packaging. However, the current die-attach techniques suffer from low thermal boundary conductance (TBC) at bonding interfaces, leading to a significant temperature rise during operation. This study examines a Cu-Cu bonding technique that achieves a low thermal budget of 150°C while simultaneously achieving an ultra-high TBC by coating Ti/Au nanolayers and Ar plasma bombardment. The overall TBC values measured for the bonded Si-Si and Si-Al2O3 interfaces were 41.49 and 34.13 MW/m2·K, respectively. These results represent a significant enhancement, by 1 to 2 orders of magnitude, compared to industry-standard die-attach technologies such as soldering and Ag-sintering. Microstructural analysis offers valuable insights into the bonding mechanism, demonstrating the diffusion of Cu atoms through the distinct Ti grain boundaries into the bonding interface, resulting in the formation of a void-free CuAu interlayer. These interlayers contribute to the improved TBC and overall bond quality. This development holds the potential to significantly enhance heat dissipation in electronic packaging.