Copper-to-copper direct bonding using different (111) surface ratios of nanotwinned copper films

Copper-to-copper direct bonding emerges to be the most important technique for fine pitch packaging in microelectronic devices. Low temperature Cu-to-Cu direct bonding by using highly (lll)-orieuted nauotwiuned Cu (nt-Cu) has been achieved because Cu (111) surface has higher surface diffusivities. To investigate the bonding effect by using different surface ratio ut-Cu, electroplating under different conditions was performed. The results indicate that bonding with higher (111)- surface ratio copper films would obtain a higher bonding strength of 15% when bonding at 300 °C.