Plasma combined self-assembled monolayer pretreatment on electroplated-Cu surface for low temperature Cu–Sn bonding in 3D integration

•Surface properties of electroplated Cu play a significant role in determining low temperature Cu–Sn bonding.•A novel pretreatment of plasma combined self-assembled monolayer (PcSAM) was proposed to improve Cu surface effectively.•With optimal PcSAM pretreatment, oxygen content of Cu surface was reduced to a lower level (1.39%).•The subsequent low temperature (200°C) Cu–Sn bonding was realized and exhibited a much higher shear strength (68.7MPa).