Low-Temperature Wafer Bonding Using Solid-Liquid Inter-Diffusion Mechanism

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.