A Low-Temperature Hybrid Bonding Using Copper and Parylene for Heterogeneous Integration

This work demonstrates a low-temperature hybrid bonding integrating copper and Parylene-C for 3-D integration. The Parylene was deposited using a chemical vapor deposition process over electroplated copper bumps followed by chemical mechanical polishing (CMP) to planarize copper/parylene topology and flatten the roughness of a copper surface. The parylene shows a higher tolerance for height topology and surface roughness. The recrystallization of the parylene was performed at 250 °C for 30 min prior to bonding. The copper and parylene materials are then bonded simultaneously at 300 °C. A homogenous bond of copper to copper and parylene to parylene bonding interface without any significant bonding voids was obtained. The tensile and shear bond strength of the bond interface was evaluated using a universal testing machine (UTM) and showed improved strength compared to bonding them separately. The thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis ensures parylene's thermal stability up to 490 °C, making the substance appropriate for IC packaging. The developed hybrid bonding is well suited for 2.5 and 3-D heterogeneous integration.