Irradiation conditions of gas cluster ion beam for surface-activated bonding

Abstract

The irradiation conditions of gas cluster ion beam (GCIB) for surface-activated bonding (SAB) were investigated. Since GCIB realizes bombardment with low energy (∼several eV/atom) and dense-energy deposition, it modifies the near-surface layer with low damage, which will be beneficial for surface-activated bonding. In this study, Cu–Cu bonding with GCIB irradiation was carried out as a preliminary study, and the irradiation conditions of Ar-GCIB were investigated. X-ray photoelectron spectroscopy (XPS) and contact angle measurements showed that the surface oxide on Cu was removed efficiently by oblique-incidence Ar-GCIB irradiations. Also, it was shown that sequential Ar-GCIB irradiations at normal and oblique incidences realized a smooth Cu surface. Cu–Cu bonding did not succeed for the pristine Cu or Cu irradiated with Ar monomer ions. In contrast, Cu–Cu bonding was realized with Ar-GCIB irradiation owing to surface oxide removal and smoothing effects.