Design, fabrication and testing of an optimized single-axis MEMS capacitive accelerometer using wet etching for improved noise stability

This study presents the design, simulation, fabrication, and experimental characterization of a single-axis MEMS capacitive accelerometer fabricated using a wet bulk-micromachining process. The proposed structure employs an enlarged proof mass and a simplified differential capacitive architecture to improve noise performance while maintaining low nonlinearity and low cross-axis sensitivity. Unlike many previously reported MEMS accelerometers that rely on complex comb-drive structures, silicon-on-insulator (SOI) wafers, or deep reactive ion etching (DRIE), the proposed device is implemented using standard silicon wafers and conventional wet etching, thereby reducing fabrication complexity. Finite-element simulations were performed in COMSOL Multiphysics to optimize the electromechanical behavior and structural parameters of the sensor. The fabricated accelerometer demonstrated a resonant frequency of 3620 Hz, nonlinearity below 0.9% full scale, cross-axis sensitivity below 0.03%, and a dynamic range of ± 10 g. The measured noise spectral density reached 18 µg/√Hz in the mid-band region, while the scale-factor sensitivity was approximately 200 mV/g with a resolution of 0.6 mg at 1 Hz bandwidth. The device also showed stable operation over a temperature range of − 20 °C to + 80 °C. In addition, finite-element simulations indicated that the structure can tolerate shock loads up to 5000 g without exceeding the silicon stress limit. The results suggest that wet bulk micromachining can enable an enlarged proof mass and reduced noise floor while preserving acceptable linearity and mechanical safety margins. Furthermore, simulations showed that the dynamic range of the proposed architecture can be tuned from ± 2 g to ± 200 g by modifying the suspension beam thickness without changing the overall device topology. These findings suggest that the proposed accelerometer is a practical and cost-effective candidate for capacitive sensing applications requiring simplified fabrication and competitive performance.