Outgassing study of thin films used for poly-SiGe based vacuum packaging of MEMS

MEMs typically have moving parts that are sensitive to the environmental pressure during operation. Many types of microsystem devices need vacuum in order to operate properly. However, making a high vacuum MEMS package, which maintains this vacuum over a long time, is difficult. Sources of gas inside a MEMS package are mainly due to external leakage or in-diffusion and/or internal materials outgassing. This paper reports on a systematical study of the outgassing properties of typical materials (Table 1) used for imec´s polycrystalline silicon-germanium (poly-SiGe) based MEMS thin film vacuum package technology.