Room temperature vacuum sealing using surfaced activated bonding with Au thin films [microresonator example]

We report surface activated bonding (SAB) using Au thin films with a thickness of a few tens of nanometers which can be applied to room temperature vacuum sealing for microelectromechanical systems (MEMS) packaging. In a previous study, it was found that room temperature bonding of Si/Si and Si/chemical mechanical polished (CMP) electroplated Cu could be successfully applied to vacuum sealing of micro cavities. However this method needs high vacuum in bonding process for keeping activated surfaces and the surfaces should be cleaned by wet processes. In this study, we attempt to realize room temperature vacuum sealing in low vacuum without any wet surface pre-treatments utilizing Au thin films with controlled surface roughness. We propose and develop packaging structures with comb-drive resonators for characterization of sealing quality and show the applicability of SAB of Au-Au thin films to vacuum-seal packaging.