Reliability assessment and failure mode analysis of MEMS accelerometers for space applications

In the present work, the reliability assessment of capacitive MEMS accelerometers of 3 different suppliers (codenamed A, B, and C) for their use in space applications was performed. The developed reliability assessment testing program addressed specific severities of space missions, such as mechanical shocks and vibrations during take-off and rocket stages separation, high temperature gradients and radiation endurance during in-orbit operation. The main aim of the testing was to evaluate the robustness and reliability limits of MEMS devices by overstressing their specific properties through dedicated tests. Typical failures modes were analyzed and root causes identified on the devices' subsystem level: MEMS structure, ASIC, interconnecting wires, and package. Overall results of the performed reliability assessment tests and failure mode analyses suggest that the most specific MEMS components, namely the microstructures, do not themselves constitute the failure causes. Following the observations, other components, e.g. interconnects, ASIC or packaging, exhibit lower reliability limits to the specific stresses of the space harsh conditions. Comparative analysis of three accelerometers from various suppliers (designs A, B, and C) suggests the design A (in a hermetic ceramic package) to exhibit the best overall reliability for space-specific application conditions. Design B also shows good robustness. However, its non-hermetic packaging makes it unsuitable for the direct use for space applications in the current state. Utilization of a hermetic package and improvement of the wire-bonding temperature resistance would significantly improve this design. Accelerometers of supplier C (in a hermetic ceramic package) have a trend of occasional "infant mortality" early failures. It is therefore very important to perform burn-in and initial pre-screening for these devices. Another strong weak point for this design is related to a low radiation endurance, which shall be significantly improved.