A piezo-capacitive BAW accelerometer with extended dynamic range using a gap-changing moving electrode

We present for the first time, a frequency-output resonant accelerometer based on the electrostatic softening effect in a bulk acoustic wave (BAW) resonator. The concept of a moving electrode is proposed to enable a self-acting linear range extension for the accelerometer. The device is fabricated in a combined piezoelectric and capacitive HARPSS platform and uses a moving capacitive electrode with nanoscale gaps (100–200nm) to extend its dynamic range. This novel moving electrode mechanism allows large scale factor for low acceleration range, at the same time reduces nonlinear gap-closing behavior at high acceleration range, thereby improving the dynamic range by a few orders of magnitude.