Ultra-smooth Cu surface fabricated by hydrodynamic suspension polishing technique

Abstract Hydrodynamic suspension polishing technique is proposed to prepare an ultra-smooth surface by designing a setup with a particular polishing disk. The novel polishing technique involves two preceding steps of mechanical polishing and chemical erosion processes. They are introduced to deal with the as-received Cu surface before the hydrodynamic suspension polishing for the polishing efficiency. Surface roughness, surface deformation layer and crystalline structures of the mechanically polished surface and the surface polished by the novel technique proposed here are characterized to show the advantages of the proposed technology. Results show that chemical erosion process efficiently removes surface deformation layer and the novel polishing process decreases the surface roughness significantly. The minimum surface roughness (Ra) is only 0.81 nm. Furthermore, there are no apparent surface deformation layers and crystalline defects on the surface after hydrodynamic suspension polishing. The relationship between the kinetic energy of abrasive and bonding energy of Cu atom is established to provide a clear understanding of the two typical planarization mechanisms, i.e., removing and filling. Both the scientific design of non-contact polishing and appropriate processing parameters are bases of preparation of the atomic-scale smooth surface. This study provides a new strategy to polish metal material with an atomic scale surface roughness and high efficiency.