A Novel Polymer-Based Ultra-High Density Bonding Interconnection

3D heterogeneous integration with advanced packaging and high-density chip stacking technologies are critical design breakthroughs to support market demand and enable success. Increasingly, hybrid bonding interconnection has been recognized as the unique bonding method that can satisfy the demand for high-density chip stacking. In this study, we demonstrate chip-to-wafer bonding with high density micro-bumping that utilizes an organic dielectric material to replace the inorganic dielectric material. This new hybrid bonding interface can exhibit improved particle sensitivity compared to oxide, along with better dielectric properties. This work demonstrates that such a bonding material has potential compatibility with both high-precision alignment at low temperatures and high-temperature copper annealing. A two-stage assembly process including pre-bond and gang bond is used to increase copper-to-copper metal solid-state diffusion to improve bond strength to nearly match that of oxide hybrid bonding. Ultimately, scratch-free copper polishing pads can provide good copper height uniformity after Chemical Mechanical Planarization (CMP) processing, allowing void free formation of polymer and copper bonds. Together, a chip bonding process was developed with a three step bonding profile to simulate NCF (Non-Conductive Film) bonding mechanism. The polymer is slightly fluid during thermal-compression bonding allowing it to fill completely into all bonding interfaces.