A micro-machined differential resonance accelerometer based on silicon on quartz method

- The micro-machined resonance accelerometer in differential configuration working in air is proposed, modeled and characterized.
- SOQ (silicon on quartz) method is introduced in the sensor, which combines the silicon spring-mass and quartz double ended tuning fork (Q-DETF) resonator.
- Piezoelectricity of quartz material is used in the driving and sensing of the resonator.
- Dual Q-DETFs are bonded in the same plane at the middle of proof mass thickness along the diagonal line of square poof mass.
- The highly symmetrical configuration of the sensor can eliminate the main disadvantage of SOQ method, which is verified by experiment.

This paper describes a micro resonance accelerometer working in air with differential configuration using silicon spring-mass and quartz double ended tuning fork (Q-DETF) resonator. When acceleration is applied in sensing direction, the inertial force of proof mass will apply axial force on Q-DETFs, which shifts the resonance frequency of Q-DETFs. Dual Q-DETFs, working in differential condition, are bonded in the same plane at the middle of proof mass thickness along the diagonal line of square proof mass. The configuration has the advantage that the inertial force of proof mass is mostly applied along the axis of Q-DETF tines when acceleration is applied in sensing direction, and the bending of DETF induced by acceleration in sensing direction is very small so that it can be neglected, which can improve sensor nonlinearity. The highly symmetrical configuration of the sensor can better eliminate most of common-mode disturbance, especially temperature and residual stress. Theoretical analysis on sensitivity is conducted and the result matches well with experimental data. The sensor is fabricated and characterized in air using rotary experiment in earth gravitational field. In the experimental range of ±1g, the tested sensitivity, nonlinearity and hysteresis are 6.317 Hz/g, 0.26% and 0.09%, respectively. The sensor stability in 12 h is also tested in air under the influence of temperature turbulence and residual stress and the drifting of sensor output is less than 0.5 Hz.