A Low-Temperature SU-8 Based Wafer-Level Hermetic Packaging for MEMS Devices

We have developed a novel all SU-8 packaging method for microelectromechanical system (MEMS) devices. The process is low temperature and low cost and it allows for nonhermetic as well as hermetic packaging. The nonhermetic package can be applied to sensors. The process flow is based on a partial and a full exposure of SU-8 negative resist using two masks. The underexposed region results in cross-linking of only a surface layer, while the underlying resist is not cross-linked and can be removed using SU-8 developer. By depositing a second SU-8 layer a sealed package for MEMS devices can be achieved. The packaging method provides any pattern and cavity clearance since it is solely based on lithography steps. The concept of the packaging method is introduced in this paper and then its practical validity demonstrated using simulation and characterization results.