Packaging effects on MEMS pressure sensor hysteresis

Micro-electro-mechanical systems (MEMS) have allowed high precision pressure sensors to be manufactured at low cost, but they typically exhibit some level of hysteresis behaviour, which is believed to be primarily due to the materials used to package them. In order to evaluate the effects of the different packaging materials and processes, in this study, the performance of piezoresistive absolute pressure MEMS was measured for each of the first two packaging stages of the product assembly process. Sensing elements first packaged in a “floating exposed” configuration and then in an “attached exposed” configuration were compared. These two different packaging configurations exhibited distinct hysteresis behaviour when thermally cycled. After applying a third order polynomial fit to the raw data, stabilized and moving hysteresis loops were observed for the floating exposed and attached exposed configurations respectively. The stabilized hysteresis is believed to originate from the inelastic behaviour of the die metallisation, whereas the nonstabilized behaviour stems from the adhesive used to attach the die to the housing.