Microstructure and mechanical properties of aluminum–germanium eutectic bonding with polysilicon metallization for microelectromechanical systems (MEMS) packaging

Wafer bonding using Al–Ge eutectic alloy was developed for the microelectromechanical system package. During bonding, Al–Ge eutectic melting primarily occurred, with an active involvement of poly-Si. Bonding microstructure consists of Al layer and Si–Ge–Al alloy layer, corresponding to the crystal structure and bonding geometry. Active reaction ensures the strong chemical bonding and reliable hermetic sealing. At the higher bonding pressure, the microstructure was slightly modified. Shear test showed a direct correlation between bonding strength and bonding pressure.