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.

Surface preparation of metal films by gas cluster ion beams using organic acid vapor for Cu–Cu bonding

“…we had shown that GCIB irradiation improved the Cu-Cu bonding strength. [15][16][17] In this study, we investigated a more efficient method for the removal of the surface oxide layer. To remove the oxide layer, we used acetic acid vapor during GCIB irradiation.…”

Gas-cluster ion sputtering: Effect on organic layer morphology

“…Irganox 1010 has been used as a standard material for soft-sputtering and to establish GCIS rates, 15 yet there has been little work published to understand how the surface structure is changed by cluster sputtering. Sputter-induced changes in morphology have been demonstrated in mixed polymer blends, 16 on copper surfaces, 17 with choice of ion species. 18,19 These first studies have shown that sputtering by some cluster sources can increase sample roughness.…”

Flattening of copper surfaces with a low energy xenon-ion source generated by photoemission-assisted plasma

“…7) In the case of Cu-Cu bonding at RT, R q should be also reduced below 1-2 nm to achieve a tensile strength of more than 200 MPa. 8,9) Surface cleaning and flattening for SAB have been performed by dry processes with energetic atom and ion beams: FAB, 7,8) gas cluster ion beam (GCIB), 9,10) Kaufmantype broad beam ion source, 11) and end-Hall ion source. 12) Such energetic beam sources are used at an ion energy, E ion , of 0.1-5 keV at grazing incident angles to obtain a high sputtering yield.…”