Direct bonding is now a well-known technique to join two flat surfaces without any additional material. This technique is used in many applications and especially in SOI (Silicon-On-Insulator) elaboration or in some backside imager manufacturing processes which are now almost in mass production. Direct bonding mechanism study is then very important in order to clearly understand this bonding behavior. Especially in the case of silicon or silicon dioxide hydrophilic surface, the role of water is essential. Water could lead to lots of different reactions at the bonding interface and especially the water stress corrosion could play an important role in the direct bonding mechanism.

Adhesion energy and bonding wave velocity are key parameters that should be controlled in an industrial direct bonding process because it reports what exactly occurs at the time of the bonding. While dynamics of the bonding front has been analytically studied and modelled [1-4], the literature gives not much information about its characterization. This study is then focused on adhesion energy (Ea) and bonding wave velocity (Vo) measurement. After considerations about immediate and stabilized adhesion energy, we will show the dependence between Ea and Vo and we will confirm Rieutord’s model [1] for hydrophilic direct bonding. Roughness dependence, plasma pre-treatment, hydrophobic direct bonding and re-bonding will also be discussed.