Investigation of Bonding Between Nanotwinned Cu and Nanocrystalline Cu

Cu to Cu bonding is important to advanced packaging due to its excellent conductivity and thermal stability. This study investigates the bonding characteristics and post-bonding properties of highly (111 )-oriented nanotwinned copper (NT -Cu) and nanocrystalline copper (NC-Cu) films. Shear test and FIB analyses indicate that increasing the bonding pressure to 40 MPa substantially reduces interfacial voids and enhances shear strength. Besides, at 40MPa, the bonding strength of the mixed structure (NT -Cu to NC-Cu) is better than the uniform structure (NT-Cu to NT-Cu and NC-Cu to NC-Cu), showing an enhancement between the bonding interface.