Low Temperature Cu to Cu Direct Bonding below 150 °C with Au Passivation Layer

In this research, Au is proposed as a new passivation material for Cu-Cu direct bonding. According to the TEM result, Cu could diffuse through the Au passivation layer to the bonding interface during the thermocompression bonding (TCB) process. In addition, the Au passivation layer can lower the bonding temperature (150 °C) and improve electrical properties, comparing to the conventional Cu-Cu bonding. Furthermore, the electrical measurement results after reliability tests show that the Au passivation method is a reliable way to reduce the bonding temperature of Cu-Cu direct bonding.