Conductive behavior modeling of dual-axis CMOS MEMS convective accelerometers using 3D FEM and spherical model

This paper presents heat conduction modeling of dual axis micromachined convective accelerometers. Results from FEM simulation are used to develop an analytical model of heat conduction main parameters. Two variables are used in FEM simulations: heater temperature and cavity depth. The latter parameter has a large impact on the overall conductive behavior of thermal accelerometers since it fixes the volume where the heat bubble can expand. Simulation results are used in a derived spherical model to develop an analytical expression of outer isotherm equivalent radius. The hot bubble radius and form are closely related to sensor geometry parameters and temperature. Two distinct equivalent radius modeling are studied and are used to express both heater heat transfer coefficient and common mode. These physically-based derived expressions govern the overall sensor conductive behavior. It is also shown that these derived expressions are still valid for different sensor design geometries.