Low temperature copper-copper quasi-direct bonding with ultrathin platinum intermediate layer using atomic layer deposition

We propose a low temperature bonding technique using an ultrathin intermediate layer deposited by atomic layer deposition. The ultrathin Pt film is selectively deposited on Cu surfaces without any masks. In order to reduce a deterioration of a reliability caused by impurities in the bonding interface, quasi-direct bonding was realized by thinning Pt intermediate layer. The shear strength of Cu-Cu bonding with the Pt intermediate layer achieved 9.5 MPa, which was five times higher than that without the Pt intermediate layer. We expect that the proposed bonding technique has a high potential to low temperature packaging technologies.