N+ plasma-assisted wafer bonding between silicon and chemical vapor deposition oxide at low temperature

Room-temperature bonding between low-pressure chemical vapor deposition (LPCVD) oxide and silicon has been achieved by using N+ plasma activation and chemical mechanical polishing (CMP). The bonding energy reaches the value of bulk silicon fracture energy (about 2.5 J/m2) after annealing at 400 °C for an hour, which is higher than the bonding energy between thermal oxide and silicon using the same process. The density difference is believed to be the main contributor to the enhanced bonding energy. Silicon-on-insulator (SOI) substrate is fabricated using Smart-Cut technology and then chemical mechanically polished to obtain a reasonably smooth surface for device manufacture. This low-temperature bonding process can be used in many applications, such as microelectromechanical systems (MEMS) and three-dimensional integration.