Superior performance area changing capacitive MEMS accelerometer employing additional lateral springs for low frequency applications

This paper introduces an effective and efficient microstructure of a differential area changing capacitive accelerometer to ensure low cross-axis sensitivity, high linearity and low noise figure for low frequency applications like Structural Health Monitoring and seismic sensing. The major design concern in an area dependent capacitance structure is that even small magnitude of cross axis displacement can drastically affect the sensitivity and linearity. The authors first focused their effort to obtain the guidelines for the best performance in the conventional structure of area changing capacitive sensors. The results clearly demonstrated that the existing structures used conventionally cannot meet the stringent requirements for low frequency applications. Subsequently, the various studies on the new structure proposed in this work were presented and the results are compared with latest reports for benchmarking. It has been estimated that the new structure can give cross-axis displacement as low as 0.5%, linearity of 2.53% and noise figure of 4.89 ng/Hz, the best achieved in so for. These studies clearly demonstrate that the ill effects of parasitic capacitance on voltage sensitivity and linearity can be suppressed by the new design. These results further show that the area changing capacitive structure employing additional lateral springs is a promising candidate for low frequency applications like seismography. The other major advantage of this structure is that the fabrication process flow need not be changed in the production line.