3 - Packaging related technologies

SiO₂/SiO₂ bonding: The bonding mechanism of two oxidized silicon wafers is shown on the animation below. The surface of an oxidized silicon wafer terminates at the Si dangling bonds. These bonds react rapidly with water to form SiOH groups. Therefore the surface of an oxidized wafer normally contains silicon hydroxyl groups. When the wafers are pressed together and heated, the two opposite OH groups interact forming H2O and the Si-O-Si bond (300°C).

Si/Si bonding: The bonding in the presence of native oxide is also thought to proceed via the hydrogen-siloxane bond. Heating the wafer to 200°C, the available hydroxyl groups will contribute to the attraction through hydrogen bonds. Dehydration of OH groups begins and the hydrogen bonds are replaced by the Si-O-Si bonds. At about 400°C, very strong covalent Si-Si bonds are formed.