Handbook of Silicon Based MEMS Materials and Technologies

Chapter Thirty One. Silicon Direct Bonding

Direct bonding generally means joining of two pieces together without an intermediate layer or external force. If the surfaces are flat, clean and smooth, they can stick together when brought into contact and form a weak bonding based on physical forces at room temperature. The physical forces can be van der Waals type of forces, hydrogen bonding, capillary forces or electrostatic forces [1]. Without subsequent annealing the bonding between the wafers is reversible. After wafer contacting the physical forces can be converted to chemical bonds by annealing. This may increase the adhesion between the surfaces up to the cohesive strength of the material in concern.

The type of the bonding is determined ...