Direct wafer bonding refers to a process by which two mirror-polished wafers are put into contact and held together at room temperature without any additional materials. This technology is feasible at an industrial scale and compatible with the microelectronic processes. Wafer bonding finds many interests applied to innovative substrates realization. Therefore the use of direct wafer bonding is growing and extending to various materials. Since few years direct bonding involving metallic layers presents many interests as it can offer, for example, vertical electrical conduction or heat dissipation. The aim of this work is to analyze the bonding behavior and to propose a first model describing the bonding driving forces. A precise understanding of these mechanisms is essential for the optimization and the technological integration of the process in various devices. In this study, tungsten and titanium bonding processes were developed. Physical and chemical bonding interfaces characterizations have highlighted the key role of the metallic oxide. We showed that bonding mechanisms are driven by grain boundary diffusion phenomena and the interface trapped oxide layer instability. Moreover, mechanical and electrical properties were also studied. Finally, the bonding behavior understanding in function of define parameters lead to some recommendations for the bonding process integration achievement.
