Fine-Pitch (≤10 µm) Direct Cu-Cu Interconnects Using In-Situ Formic Acid Vapor Treatment

We demonstrate a solderless direct copper-copper (Cu-Cu) thermal compression bonding (TCB) process for die-to-wafer assembly in ambient environment using a novel in-situ formic acid vapor treatment. We show that this approach produces excellent Cu-Cu bonds with an average shear strength of >150 MPa. Using this TCB process, we demonstrate dielet assemblies on the Silicon-Interconnect Fabric (Si-IF) platform with fine-pitch (≤ 10 μm) Cu-Cu interconnects. Further, we show electrical continuity across multiple dies on the Si-IF with an interconnect specific contact resistance of <;0.7 Ω-μm ² .