Electrical Characterization of a MEMS force sensor designed and fabricated within the Next-Gen Metrology #03 project

This work presents a comprehensive electrical characterization of a MEMS capacitive force sensor designed and fabricated at INRiM. The characterization procedure determines key device parameters including ca- pacitance variations as a function of displacement, output voltage sensitivity, and the mechanical spring constant of the suspension system. A custom experimental setup integrating a transimpedance amplifier, precision capacitance bridge, and synchronized data acquisition system was employed. The displacement measurements were obtained through lock-in detection of the output signal, while the electrostatic force was calculated from the measured capacitance gradient and applied DC voltage. A full uncertainty analysis using the GUM method was performed to assess the measurement accuracy. The results demonstrate satisfactory agreement for the average values, though an in-depth analysis reveals discrepancies between the two differen- tial capacitor configurations, which are attributed to device asymmetries and measurement conditions. The extracted spring constant is k = 22.5 μN/μm with an associated uncertainty of greater than 2.3 μN/μm.