The effects of radiation on MEMS accelerometers

Exposing just the mechanical part (sensor) of MEMS accelerometers to protons and heavy ions caused large changes in outputs representing the measured acceleration for the ADXL50 and very small changes for the ADXL04. The large voltage shift measured for the ADXL50 is attributed to charge generated by the ions and trapped in dielectric layers below the moveable mass. The trapped charge alters the electric field distribution which, in turn, changes the output voltage. The construction of the ADXL04 differs from that of the ADXL50 in that the dielectric layers are covered with a conducting polycrystalline silicon layer that effectively screens out the trapped charge, leaving the output voltage unchanged.