Preferred Grain Orientation to Enhance Interdiffusion at Room Temperature in Atomic Diffusion Bonding: A Fundamental Study Using Ni and Cu Films

Abstract

The interdiffusion and interface structure at the bonded interface of Cu and Ni films obtained using atomic diffusion bonding (ADB) processing was assessed in relation to films structures used for bonding. Improvement of the (111) preferred grain orientation in Ni and Cu films used for bonding enhanced the crystal lattice rearrangement at the bonded interface of Ni–Cu bonded films, leading to large interdiffusion. The representative interdiffusion length evaluated using magnetic characterization was 5.4 nm for a Ni(20 nm)–Cu(10 nm) bonded interface with Ti underlayers. Grain boundary diffusion partially contributed to the interdiffusion length independently of the (111) preferred grain orientation of films. These results indicate that ADB bonding performance enhancement can be achieved with a high degree of (111) preferred grain orientation and low surface roughness in ADB processing using metal films having an fcc crystal structure such as Al, Au, Ag, Cu, Ni, and Pt.