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

Area of Science:

• Microelectromechanical Systems (MEMS)
• Capacitive Sensing
• Solid-State Physics

Background:

• Traditional MEMS accelerometers often require complex fabrication processes like deep reactive ion etching (DRIE) or specialized wafers.
• There is a need for cost-effective and simplified fabrication methods for MEMS accelerometers without compromising performance.

Purpose of the Study:

• To design, simulate, fabricate, and characterize a single-axis MEMS capacitive accelerometer using wet bulk-micromachining.
• To improve noise performance and maintain low nonlinearity and cross-axis sensitivity.
• To demonstrate a tunable dynamic range and cost-effective fabrication.

Main Methods:

• Utilized wet bulk-micromachining on standard silicon wafers.
• Employed an enlarged proof mass and simplified differential capacitive architecture.
• Performed finite-element simulations using COMSOL Multiphysics for optimization.

Main Results:

• Achieved a resonant frequency of 3620 Hz, nonlinearity <0.9% FS, and cross-axis sensitivity <0.03%.
• Measured noise spectral density of 18 µg/√Hz and a resolution of 0.6 mg at 1 Hz.
• Demonstrated stable operation from -20°C to 80°C and tolerance to 5000 g shock loads.

Conclusions:

• Wet bulk micromachining enables enlarged proof mass and reduced noise floor in MEMS accelerometers.
• The proposed design offers a practical and cost-effective solution for capacitive sensing.
• The dynamic range is tunable from ±2 g to ±200 g by adjusting suspension beam thickness.