Surface protection of copper by self assembled monolayer for low-temperature chip bonding

To protect the surface of electroplated Cu from contamination such as oxidation, coating of the surface with a self-assembled monolayer (SAM) was investigated. The coating material investigated was 1-Hexanethiol. Auger electron spectroscopy showed that the SAM coating definitely reduced the oxidation rate of the Cu surface. Change in surface contamination with elevating temperature in the ambient was investigated by measuring wetting angle of water. It showed that the surface protection is kept up to about 100°C. Also, we applied this coating to Cu cone-shaped bump.