High Sensitivity and Power Efficient Heater Structure for Bulk Micromachined Thermal Accelerometer

Abstract

In MEMS based thermal convective accelerometers, the structure of the constituent microheater plays a crucial role in determining the sensitivity of the accelerometer. This paper reports the sensitivity improvement of a dual axis thermal accelerometer using a cross shaped heater structure. In a conventional heater design, the peak heater temperature generated at the center of the cavity offers lower temperature gradient at the position of the temperature sensors situated afar. As a result, the sensitivity obtainable from the thermal accelerometer becomes low. The sensitivity can be improved by generating the peak temperature at the side arms which are used to suspend the heater structure. This has been accomplished in this work using a cross shaped heater where the peak temperature is generated at the cross arms of the heater. Hence, the temperature gradient is higher near the temperature sensors, leading to improved sensitivity of the accelerometer. The sensitivity achieved using such a cross shaped heater is 0.36 K/g at a peak heater temperature of 615 K and having power requirement of 29.6 mW. The proposed heater structure can also be employed in other microsystem devices like gyroscope and thermal flow sensor for improving their performance.