Copper-to-copper direct bonding on highly (111) oriented nano-twinned copper in no-vacuum ambient

In this study, we achieve the Cu-to-Cu direct bonding by using the (111) oriented nano-twined-Cu in N2 ambient, without vacuum condition and no additional thermal annealing treatment is needed. A well bonded interface under a temperature gradient between 400 °C and 100 °C was identified by the evidence of the grown grain across the bonding interface. In addition, a creep assisted bonding mechanism for the Cu-Cu direct bonding is proposed. Moreover, a shear test was applied on the bonded joints for the investigation of the bonded joint strength and its fracture mode. The mean value of joint strength is 176 MPa which is significantly higher than the conventional solder joint. In summary, the Cu-to-Cu direct bonding by (111) oriented nt-Cu in no-vacuum ambient as well as the grain evolution across the bonding interface has been achieved and verified.