Silicon-to-silicon direct bonding method

It was found that strong bonding takes place when a pair of clean, mirror-polished silicon surfaces are contacted at room temperature after hydrophilic surface formation. Bonding strength reaches the fracture strength of silicon bulk after heating above 1000 °C. Electric resistivity at the interface is less than 10−6 Ω/cm2. Bonding p-type silicon to n-type silicon forms a diode. The reaction between silanol groups formed on the surface may cause the bonding force. Heating above 1000 °C was thought to diffuse oxygen to inside the silicon bulk, forming an epitaxial-like lattice continuity at the interface.