First Demonstration of Enhanced Cu-Cu Bonding at Low Temperature With Ruthenium Passivation Layer

In this work, we studied the characteristics of Cu-Cu bonding with a ruthenium passivation layer at low temperatures. It is confirmed that the ruthenium passivation layer is effective in preventing the formation of native copper oxide, and diffusion of the copper into the ruthenium passivation layer occurred sufficiently at 200°C. The Cu samples with the ruthenium passivation layer were successfully bonded at 200°C. They exhibited excellent shear strength of 17.16 MPa, and the specific contact resistance of 1.78\times 10 ^-7~\Omega \cdot cm2 at the bonding interface. With the results, we expect that along with improving the thermal budget of the bonding process, it will be able to contribute to improving the chip performance and reliability of heterogeneous integrated structures.