Low Temperature Cu-Cu Bonding with Electroless Deposited Metal Passivation for Fine-Pitch 3D Packaging

In this study, electroplated Cu-Cu bonding with electroless plating passivation on Cu surface can be achieved at a low bonding temperature. Compared with other low temperature bonding schemes, electroplated Cu and electroless plated passivation in this work is time-saving, high throughput, and high yield. After a pretreatment process, chip-level bonding with the good bonding quality can be achieved at 180°C under atmosphere. The morphology of the electroless plated passivation surface was characterized by the energy dispersive X-ray spectroscopy (EDX), and the bonding quality was investigated by the analyses of scanning electron microscope (SEM). In addition, electrical measurements were performed to evaluate the electrical properties of the bonding structure.