In advanced microsystems various types of devices (metal-oxide semiconductor field-effect transistors, bipolar transistors, sensors, actuators, microelectromechanical systems, lasers) may be on the same chip, some of which are 3D structures in nature. Therefore, not only materials combinations (integrated materials) are required for optimal device performance of each type but also process technologies for 3D device fabrication are essential. Wafer bonding and layer transfer are two of the fundamental technologies for the fabrication of advanced microsystems. In this review, the generic nature of both wafer bonding and hydrogen-implantation-induced layer splitting are discussed. The basic processes underlying wafer bonding and the layer splitting process are presented. Examples of bonding and layer splitting of bare or processed semiconductor and oxide wafers are described.

Low‐temperature wafer direct bonding is considered a key tool for the fabrication of bulk micromechanic devices. The possibility of enhancing the bonding energy by applying an O2 plasma treatment before bonding has been the focus of recent studies. Here, the effect of storage following the plasma treatment, as well as the duration of the latter on the attainable activation of the surface, the bonding strength, and bubble generation, have been investigated. Immediately after the plasma treatment bond energies up to 1.6J/m2 are achieved. However, 50 h after the treatment bonded wafer pairs show bonding energies up to only 1.3J/m2 . The duration of the plasma treatment strongly affects the number, size, and distribution of interface bubbles. © 2000 The Electrochemical Society. All rights reserved.