This paper demonstrates a novel wafer bonding method using nano-adhesion layer for SiO2 to SiO2 room-temperature bonding without heat treatment. The bonding energy of the bonded wafers increases significantly owing to adding Si intermediate layer and Fe nano-adhesion layer by ion beam treatment. As the results, very strong bonding strength (∼2.2 J/m2) of SiO2-SiO2, SiO2-SiN, and SiN-SiN pairs, close to the bulk-fracture strength of silicon, is achieved at room temperature by nano-adhesion of Si intermediate layer. The wafer surfaces and the bonding interfaces are investigated by X-ray photoelectron spectroscopy (XPS), Radio Frequency Glow Discharge Spectrometer (RSGDS), high-resolution transmission electron microscopy (HRTEM), and electron energy-loss spectroscopy (EELS), respectively. The Si intermediate layer results in Fe-doped on the Si layer surface, which may affect the surface energy on the bonding wafers. In addition to Si layer, an amorphous Fe-doped Si layer is formed at the bonding interface, which also result in a strong bonding strength at room temperature.
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