Formation of the Cu6Sn5 Intermetallics in Cu/Sn Thin Films

The formation of the Cu6Sn5 intermetallic in Sn(55nm)/Cu(30nm) thin-film bilayers has been studied upon heating the film sample from room temperature to 300 degrees C directly in a column of a transmission electron microscope in the electron diffraction mode with recording electron diffraction patterns. The thin films synthesized by the solid-state reaction have been found to be single-phase and consist of the eta-Cu6Sn5 hexagonal phase (95-260 degrees C). It has been suggested basing on the effective interdiffusion coefficient (5 x 10(-16) m(2)/s) estimated in the course of the reaction that the main mechanism of the formation of the Cu6Sn5 thin films is diffusion along grain boundaries and dislocations.