A double differential torsional accelerometer with improved temperature robustness

• This paper reports the design, realization and characterization of a novel MEMS accelerometer with improved temperature robustness.
• While torsional accelerometers have lots of advantages, significant challenges remain in increasing their long term and temperature robustness.
• This paper proposes double differential configuration and on-chip reference capacitor configuration to improve the temperature robustness.

This paper reports the design, realization and characterization of a novel double differential torsional MEMS accelerometer with improved temperature robustness. Based on the structure of conventional torsional accelerometers, normally composed of two unbalanced proof masses and an identical torsional beam, this work explores a torsional accelerometer with two structural optimizations aiming to improve the temperature robustness: a double differential configuration and an on-chip integrated reference capacitor configuration. The double differential configuration realizes the temperature self-calibration by making the two pairs of unbalanced masses have the same sensitivity to temperature but opposite sensitivity to acceleration. And the on-chip integrated reference capacitor realizes the temperature self-calibration by transferring the temperature dependent reference capacitor from ASIC or PCB into the MEMS structure. Totally ten accelerometer prototypes are fabricated with the pre-buried mask wet-etching method and tested. Comparison tests show that, for most of the accelerometers, by taking the double differential configuration and the on-chip integrated reference capacitor configuration, the temperature sensitivity of the scale factor, the bias stability and the output drift of in the full temperature range are greatly improved. The testing results experimentally demonstrate the effectivity of the optimization for improving temperature robustness.