Investigation of fluorine containing plasma activation for room-temperature bonding of Si-based materials

Wafer direct bonding of Si based materials, such as silicon, silicon oxide and silicon nitride, is a generic technique enabling realization of innovative structures in semiconductor industry. In this paper, a fluorine containing plasma activated bonding method is developed to achieve sufficient bonding at room temperature in air ambient with no heating process. The whole process is facile and cost effective without requiring high-vacuum system. It does work well for bonding of Si-based materials except for Si3N4/Si3N4 bonded pairs. The bonding strengths of specimens prepared by fluorine containing oxygen plasma are significantly improved at room temperature compared with those by oxygen plasma. The improved bonding strength is possibly attributed to the formation of fluorinated oxide layers on wafer surfaces after the plasma treatment.