Radiometric effects in MEMS accelerometers

MEMS (mico-electro-mechanical systems) accelerometers must meet rigorous performance requirements for future applications like indoor navigation. To further improve the sensors performance new effects like radiometric forces have to be considered. Small temperature gradients within the sensor package caused by outer or inner heat sources will cause noncontinuum gas flows inside the sensor leading to offset deviations in the sensor signal. So far, the impact of temperature gradients on acceleration sensors is not investigated in great detail. First, we introduce a measurement setup to characterize the radiometric effects for packaged sensors. Second, we show that the offset deviation vs. pressure shows a bell shaped function which linearly scales with the temperature gradient. Third, we give three ways to reduce the effect by changing the cavity pressure, gas type or symmetrizing the MEMS design. Those optimization options will improve the sensor robustness against inhomogeneous temperature distributions.