The discrete vacuum packaging reliability issue in MEMS

Packaging of Micro Electro Mechanical Systems (MEMS) requires technical challenges to be solved and overcome when stringent vacuum and hermetic sealing is required. This is typical for a wide class of sensors, such as inertial sensors, IR micro-bolometers, MEMS atomic clocks, where such conditions need to be achieved to guaranty the performance stability during the devices lifetime. Vacuum hermetic packaging can be successfully achieved by dedicated getter film integration, key technology for vacuum requirements, in combination with a specific sealing process. In order to get reliable, void-free hermetic package and vacuum controlled atmosphere inside MEMS devices, the fundamental parameters that need to be considered and optimized are: vacuum compatibility of materials typically used in vacuum packaging, like die attach epoxies and solders, optimization of outgassing procedures before and during hermetic sealing as well as getter activation for optimal vacuum level. Moreover, capabilities of performing residual gas analyses and leak rate measurements of sealed devices are fundamental for quality control of vacuum sealing as well as for analyses and prediction of device lifetime. In this review we are presenting SAES' methodology to achieve successful discrete MEMS vacuum packaging with extended life time performances.