Three-dimensional placement rules of Cu₆Sn₅ textures formed on the (111)_Cu and (001)_Cu surfaces using electron backscattered diffraction

Highlights: • Regular arrays of Cu₆Sn₅ textures on the (111)_Cu and (001)_Cu surfaces are studied by electron backscattered diffraction. • 3D placement rules are proposed to explain the formation reason of Cu₆Sn₅ textures on the (111)_Cu and (001)_Cu surfaces. • Cu₆Sn₅ textures on (111)_Cu surfaces are more suitable for use as interfacial layers to resist shear failures in 3D-ICs. In this work, the grain orientations and surface characteristics of Cu6Sn5 textures formed at the liquid-Sn0.7Cu |(111)_Cu and liquid-Sn0.7Cu |(001)_Cu joint interfaces were systematically investigated using the electron backscattered diffraction technique. The results showed that there were two dominant reasons for formation of the strong Cu6Sn5 textures on the (111)_Cu and (001)_Cu surfaces: (1) the low but not minimum lattice matches of Cu atoms between Cu6Sn5 and Cu phases in the in-plane orthogonal directions and (2) the axial growth behaviour of Cu6Sn5 phase. Based on these reasons, we proposed and verified two types of the three-dimensional placement rules of Cu6Sn5 textures to reveal the nucleation behaviour of Cu6Sn5 on Cu surfaces. In addition, the macroscopic shear strengths of Cu6Sn5 textures on the actual joint interfaces were also tested. Our study may help clarify the epitaxial growth mechanism of Cu6Sn5 phase on the (111)_Cu and (001)Cu surfaces and provide a strong scientific basis of Cu6Sn5 orientation design for three-dimensional integrated circuit interconnect applications.