Self-formed submicron-scale faceted copper particles on the surface of annealed Cu-Zr films

Regularly faceted copper (Cu) particles ranging from tens of nanometers to submicron were obtained by annealing Cu-Zr films on polyimide and single Si (100) substrates. XRD, TEM, SEM and EDS were used to characterize their microstructural properties. The results show that these particles are pure Cu element and single crystals with [111] preferred orientation. Systematical analysis demonstrates that the sizes of Cu particles are closely related to the film composition as well annealing conditions. Specifically, larger Zr contents will suppress the grain growth, and thus lead to smaller Cu particles, while the higher annealing temperature is easier to activate atomic diffusion, and larger particles appear. In addition, the shapes of these Cu particles are also very sensitive to the microstructural properties of the thin films, the substrates types as well as annealing atmosphere. These aspects will be discussed in detail according to the morphological characteristics and residual stress evolution. This work may provide a new approach to prepare regular metal particles with sizes ranging from tens of nanometers to submicron.