Protecting a MEMS device from excess pressure and shock

摘要

A MEMS device, especially a MEMS capacitive transducer, is provided with increased robustness and resilience to acoustic shock. The transducer structure includes a flexible membrane 101 supported between a first volume 109 and a second volume 110. At least one variable vent structure 401 supplements the usual bleed holes 115 and comprises at least one moveable portion which is moveable in response to an excess pressure differential across the moveable portion so as to vary the size of a flow path through the vent structure. The variable vent may be part of the diaphragm 101 or it may lie elsewhere in the device (1101, fig 11). The variable vent 401 is preferably closed in the normal range of pressure differentials but opens at high pressure differentials to provide more rapid equalisation of the air volumes above and below the membrane. A variety of vent shapes are discussed.