Chipping Energy Threshold in MEMS Sensors

This research faces the problem of identifying the impact energy for which silicon chips are generated after shocks in microdevices, with the aim of providing design guidelines for next generation robust inertial sensors. The issue is tackled through the design of an on-chip test structure capable of generating up to 100 nJ of impact energy onto a stopping bump, corresponding to 10(3)-10(-4) gravity units of acceleration for a wide range of state-of-the art gyroscopes and accelerometers. The additional challenge of identifying the presence of debris without the need to uncap the dice is faced through the design of interdigitated electrodes underneath the impact area, and the measurement of small leakage currents caused by debris-induced short circuits between them. Statistical tests performed on 27 samples of different bump shape not only enable to identify an energy threshold for debris generation at about 10 nJ, valid at least for the considered process, but also suggest how the bump shape significantly influences this phenomenon.