Wafer bonding: a flexible approach to materials integration

“Wafer bonding” refers to the phenomenon that mirror-polished, flat and clean surfaces of almost any material, when brought into contact at room temperature, are locally attracted to each other by van-der-Waals forces and adhere or bond to each other. Semiconductor wafer bonding has increasingly become a technology of choice for materials integration in microelectronics, optoelectronics, and microelectromechanical systems (MEMS). The presentation gives an overview of the fundamentals of wafer bonding and discusses the different approaches used for silicon wafers (usually bonded at room temperature in air) and for III-V compound wafers (often bonded at elevated temperatures around 500°C in hydrogen). A critical assessment is given of so-called “universal compliant substrates” fabricated by twist wafer bonding, which are supposed to allow heteroepitaxial growth of materials with large misfit without the generation of threading dislocations