Room temperature SiO2 wafer bonding by adhesion layer method

This paper demonstrates a novel wafer bonding method using nano-adhesion layer for SiO
₂
to SiO
₂
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/m
²
) of SiO
₂
-SiO
₂
, SiO
₂
-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.