Comparative Study on System Model and Finite Element Analysis of a Monolithic 3DOF MEMS Capacitive Accelerometer

This paper presents a comparative study on the design of a monolithic 3DOF MEMS capacitive accelerometer using both analytical and numerical techniques. Monolithic accelerometer is a single structure having three individual single axis accelerometers on a single substrate and utilizes a surface micromachining technology using standard PolyMUMPs process. The designed accelerometer is 3mm×3.1mm in size, has 10.17¿ g/¿Hz and 17.50¿ g/¿Hz mechanical noise floor for in-plane and out-of-plane axes respectively. The total sense capacitance along x, y and z-axes is 68.5fF, 82.3fF and 6.19pF respectively. Sensitivity of 0.65fF/g, 0.78fF/g and 0.90pF/g is obtained for in-plane (x and y) and out-of-plane (z) axes respectively. Performing a detailed finite element analysis in ANSYS software, a displacement of 19.058¿m, 20.392¿m and 1.318¿m for x, y and z axes respectively are calculated approximately the same as calculated analytically under applied acceleration to the proof mass of the proposed accelerometer.