A low noise capacitive MEMS accelerometer with anti-spring structure

Abstract

This work reports a capacitive MEMS accelerometer designed for seismic applications. The asymmetrical anti-spring structure is used and the device is microfabricated using SOI technology. Two capacitive readout methods, namely, capacitance-to-voltage-converter (CVC) and a commercial sigma-delta modulator, are introduced for comparison in the device characterization. For both methods, the accelerometer has a frequency dynamic range of 0-158 Hz. The sensitivity and non-linearity of the sensor is 53 fF/g (21.3 mV/g), 0.03% by the sigma-delta modulator, while the CVC method is 3.78 mV/g with the non-linearity 0.04%. As for the resolution, both methods have detected the lab's background noise of 11.5 μg/Hz at 0.03 Hz and have exhibited the resolution of the sensor is better than 10 μg/Hz. Regardless of the difference in parameter selection for the circuits, the CVC method has a much lower noise floor (51.8 ng/Hz at 1 Hz) than sigma-delta readout configuration (10 μg/Hz at 1 Hz). The proposed MEMS accelerometer based on anti-spring structures shows its high sensitivity and low noise performance, demonstrating its potential in seismic applications.