Empirical model for substrate resistivity influence on MEMS capacitive accelerometer performance

Resistivity of the substrate is a key parameter in designing MEMS devices and affects the device performance. Yet, the effects of this parameter on capacitive MEMS accelerometer performance hasn’t gotten enough research. In this paper an empirical model for predicting the substrate resistivity impact on MEMS capacitive accelerometer parameters has been developed which include rest capacitance, offset, output noise and scale factor. Also, a stability analysis of MEMS capacitive accelerometer as a function of the substrate’s doping concentration was modeled, simulated and then verified by fabricating a z-axis capacitive accelerometer. In the experiment, the rest measured capacitance of accelerometer’s top plate was 11.50 pF in positive voltages and 11.97 pF for negative voltages. Also, the rest measured capacitance of the bottom plate was 11.45 pF for a positive bias and 11.92 pF for a negative bias. The measured pull in voltage was −18 V. Overall, a good agreement between the model and experimental data was obtained. Finally, minimum required substrate doping concentration (MDC) was modeled for the best performance of MEMS capacitive accelerometers which is dependent on the accelerometer’s application and resolution.