Submicron Cu/Sn Bonding Technology With Transient Ni Diffusion Buffer Layer for 3DIC Application

A submicron Cu/Sn bonding with transient Ni buffer layer at 225 °C is demonstrated to overcome current 5-μm Cu/Sn physical limitation. The 10-nm Ni layer suppresses immense Cu/Sn interdiffusion during heating step prior to major bonding process. When the temperature is close to the Sn melting point, the Ni layer dissolves and molten Sn gives successful submicrometer Cu/Sn bonding. The excellent mechanical strength and electrical performance of this scheme show the great potential for future and highly dense 3D interconnects.