Nanoprecision aligned wafer direct bonding and its outlook

A nanoprecision aligned wafer bonding is presented enabling creating innovative nanostructures. To achieve high-precision wafer bonding, a perfect alignment as well as room-temperature bonding process is necessary. In this paper, the limit of typical alignment methods is addressed firstly and a moire fringe assisted alignment method is developed to breakthrough the limit. Moreover, in order to realize room-temperature bonding without heating, a fluorine containing plasma activation is developed to combine silicon and silicon oxide wafers in air. On the other hand, a process flow consisting of the precise alignment and room-temperature bonding processes with in-situ strategy is demonstrated to realize the nanoprecison aligned wafer bonding. The proposed strategy provides one of possible solutions for development of aligned wafer bonding tools, which will open up opportunities in 3D integration circuits, 3D photonic crystals, and advanced nanotransistors.