Low-Temperature Quasi-Direct Copper–Copper Bonding with a Thin Platinum Intermediate Layer Prepared by Atomic Layer Deposition

Abstract

A low-temperature Cu–Cu bonding technique using a thin metal intermediate layer deposited by atomic layer deposition (ALD) was developed. A thin Pt intermediate layer was selectively deposited on the Cu surface at the angstrom level by ALD without any mask under low vacuum conditions (24 Pa). To suppress the deterioration of bonding reliability caused by impurities at the bonding interface, quasi-direct bonding was realized by using a thin Pt intermediate layer. The Cu–Cu quasi-direct bonding with a thin Pt layer provided a bonding strength of 9.5 MPa, which was five times higher than that without the intermediate layer (1.9 MPa). These results will contribute to the development of low-temperature Cu–Cu bonding for three-dimensional integrated circuit chips.