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

Abstract

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 (111)-oriented nanotwinned Cu (nt-Cu) has been achieved because Cu (111) surface has higher surface diffusiyities. To investigate the bonding effect by using different surface ratio nt-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% w hen bonding at 300 degrees C.