Temperature robustness design for double-clamped MEMS sensors based on two orthogonal stress-immunity structure

In micro-electro-mechanical system devices, the thermal stress and deformation caused by ambient temperature variation are of great concern since they can directly affect the performance of the devices. This paper presents an optimized temperature robustness design for double-clamped micro-structures. Robust operation over temperature is a critical criterion for most MEMS sensors, however different thermal mechanical properties of multi-layers structures will definitely cause internal stress and induce geometrical parameters deviated from the desired values which will result in frequency shift and affect the performance. Thus, an optimized strategy was proposed by integrating an orthogonal stress-immunity structure to control and eliminate these effects on double-clamped sensors. Furthermore, an optimized butterfly gyroscope was designed and fabricated to validate the improvement of this novel approach. Experimental results indicated that this novel strategy could effectively improve the temperature robustness of double-clamped micro-fabricated sensors. Also, the frequency split stability of the two vibration modes has been improved obviously (from 29.3Hz to 3.81Hz) while the drive mode frequency shift has decreased from 41.3Hz to 12.8Hz.