Abstract

We investigate a surface-micromachined capacitive accelerometer with the grid-type electrodes surrounded by a perforated proof-mass frame. An electromechanical analysis of the microaccelerometer has been performed to develop analytical formulae for the natural frequency and output sensitivity response. A set of prototype devices has been designed and fabricated based on a 4-mask surface-micromachining process. The resonant frequency of 5.8±0.17kHz and the detection sensitivity of 0.28±0.03mV/g have been measured from the fabricated devices. The parasitic capacitance of the detection circuit with a charge amplifier has been measured as 3.34±1.16pF. From the uncertainty analysis, we find that the major source of the uncertainty in the natural frequency of the accelerometer comes from the uncertainty in the beam width patterning process. The primary variables in the sensitivity uncertainty include the parasitic capacitance, inter electrode gap and resonant frequency, contributing to the overall sensitivity uncertainty in the portions of 75%, 14% and 11%, respectively.

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