Invetigation of Temperature Sensitivity of a Geomteric Anti-Spring based MEMS Gravimeter

Abstract: This paper describes a temperature sensitivity or thermal sag measurement of a geometric anti-spring based micro-electromechanical system (MEMS) gravimeter (Wee-g). The Wee-g MEMS gravimeter is currently fabricated on a (100) silicon wafer using standard micro-nano fabrication techniques. The thermal behavior of silicon indicates that the Young's modulus of silicon decreases with an increase in temperature (around 63 ppm/K). This leads to a softening of the silicon material resulting in the proof mass (PM) displacing (or sagging) under the influence of an increasing temperature. It results in the change on the measured gravity and it is expressed as a temperature sensitivity in terms of change in gravity per degree temperature. The temperature sensitivity for the silicon based MEMS gravimeter is found to be 60.14-64.87 muGal/mK, 61.76 muGal/mK and 62.76 muGal/mK for experimental, finite element analysis (FEA) simulation and analytical calculations respectively. It suggests that temperature sensitivity is depended on material properties used to fabricate the MEMS devices. In this paper the experimental measurements of thermal sag are presented, along with analytical calculations and simulations of the effect using FEA (finite element analysis). The bespoke optical measurement system to quantify the thermal sag is also described. The results presented are an essential step towards the development of temperature insensitive MEMS gravimeters.