This study of atomic diffusion bonding of Si wafers in vacuum using thin Nb films reveals remarkably high bonding strength, greater than fracture strength of a Si wafer, obtained using Nb films at thicknesses of 1.7-20 nm on each side. Transmission electron microscopic cross-section images show no vacancy at the bonded interface. Particularly, crystal lattice rearrangement occurs to a remarkable degree at the bonded interface of 10 nm thick Nb films. Surface roughness reduction is likely to enhance the crystal lattice rearrangement at the bonded interface, even with thick Nb films.
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