Room temperature bonding of silicon and lithium niobate

The feasibility of wafer-level bonding was examined for silicon (Si)/lithium niobate (LiNbO3) wafers by using a modified surface activated bonding process at room temperature. A low energy argon ion source of 80 eV energy with 3 A current was used, which was capable of sputter cleaning and depositing Fe nanolayers on the surfaces. Visual inspection showed that almost all of the 4 in. Si/LiNbO3 wafers were bonded. The measured bond strengths were as high as 37 MPa but were inhomogeneous. This is due to the lack of uniform application of force over the surfaces (which are not parallel to the jigs) and the pulling angles during the pulling test. A 5 nm thick amorphous layer was observed across the Si/LiNbO3 interface. Electron energy loss spectroscopy analysis confirmed the presence of Fe in the interfacial amorphous layer. This Fe-containing interfacial layer appears to be responsible for the high bonding strength observed between Si/LiNbO3 at room temperature. (c) 2006 American Institute of Physics.