Sensitivity modeling of dual-axis CMOS MEMS convective accelerometers using FEM and spherical model

This paper presents sensitivity behavior study and optimization of dual axis CMOS MEMS convective accelerometers using both analytical and FEM techniques. In a first part, newly developed accelerometer 3D model is used in FEM simulations. Using different sizes for micromachined and square cover shapes, it is found that sensitivity readings and its maximum position in cavity are affected by both cover size and shape. In addition, micromachined bottom cavity, with half width of 300μm, is found to produce sensitivity saturation starting at a depth of 200μ for both cover shapes. The used cover size is that offering maximum sensitivity readings. From computed heating efficiency values, it is concluded that dual axis accelerometers are more power efficient than single axis ones. In the second part, we present Hardee´s spherical model and investigate its possible application on the dual axis accelerometer. It is concluded that inner and outer isotherms deformation should be modeled by including sensor geometry parameters in governing equations.