Wafer bonding for integrated materials

Wafer bonding and layer transfer technology has emerged as one of the fundamental technologies for the fabrication of integrated materials. In this paper, we will first discuss the basics and the generic nature of the wafer direct bonding process in terms of inter-molecular forces, surface mechanics and chemistry, interface reactions and bonding procedures. Based on the understanding of wafer bonding process, innovative low temperature wafer bonding technologies that operate at wafer level in ambient conditions have been developed to facilitate the integration of almost any materials that are similar or dissimilar. Room temperature chemical bonding and low temperature epitaxial or hetero-epitaxial-like bonding approaches are introduced. Finally, examples of integrated materials prepared by wafer bonding and layer transfer are presented.