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Low-temperature wafer bonding using solid-liquid inter-diffusion mechanism

: Froemel, J.; Baum, M.; Wiemer, M.; Gessner, T.


Journal of Microelectromechanical Systems 24 (2015), Nr.6, S.1973-1980
ISSN: 1057-7157
ISSN: 1941-0158
Fraunhofer ENAS ()

The low temperature joining of semiconductor substrates on wafer level by solid-liquid inter-diffusion bonding using the Cu/Ga and Au/In systems is investigated regarding the bonding parameters and their influence on bond interface properties. The focus is on temperature dependence and composition of interface. In the case of Cu/Ga bonding, a phase transition from CuGa2 to Cu9Ga4 was found to be primarily responsible for an increase in bonding strength. After the temperature treatment of 90°C, a shear strength of up to 90 MPa could be achieved. Furthermore, the combination of Au and In with composition ratios suitable for AuIn2 and AuIn intermetallic phase formation was investigated. In the case of AuIn shear strength, 96 MPa was achieved using a bonding temperature of 200°C.