Room temperature wafer bonding using surface activated bonding method

The bonding possibility of Si-Si/Au-Au/Cu-Cu wafers is confirmed at room temperature using surface activated bonding method. The surface condition and the thickness of surface contamination of Si, Au and Cu are evaluated using X-ray photoelectron spectroscopy. Various parameters, such as vacuum pressure, bonding time, bonding load, and bonding temperature, are studied in Si-Si wafer bonding. In the case of Au-Au and Cu-Cu wafer bonding, the influence of bonding temperature is investigated. Vacuum pressure is an important factor for room temperature Si-Si wafer bonding, whereas it is not sensitive in the case of Au-Au and Cu-Cu wafer bonding. The bonding energy of bonded Si-Si wafers can be obtained more than 1.95 J/m² under the vacuum pressure of 2.5 times 10^-6 Pa. Heating at 200degC may improve the bonding strength of Au-Au and Cu-Cu wafers, however it is not useful in Si-Si wafer bonding. At room temperature, the bonding strength of the bonded Si-Si wafer reaches 16.0 MPa, and that of bonded Au-Au wafer reaches 12.4 MPa.