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

Low temperature bodings of Cu by gas cluster ion beam (GCIB) irradiations with organic acid vapor were studied. GCIBs induce surface smoothing and enhancement of surface reactions without severe damage. Therefore, it is promising for the surface activated bonding (SAB). In this study, organic acid vapor is introduced during GCIB irradiation in order to assist surface oxide removal on metal films (such as Cu, Ni). From XPS study, NiO layer was selectively removed by reaction with adsorbed organic acid. Preliminary bonding experiment using this technique shows promising result for Cu-Cu bonding.