Design and modeling of a single-mass biaxial capacitive accelerometer based on the SUMMiT v process

Serrano-Vázquez, F. X. and Herrera-May, A. L. and Bandala-Sánchez, M. (2013) Design and modeling of a single-mass biaxial capacitive accelerometer based on the SUMMiT v process. Microsystem Technologies, 19 (12). pp. 1997-2009. ISSN 0946-7076

Abstract

This paper presents the design of a biaxial capacitive accelerometer that takes advantages of a single-mass configuration to provide two orthogonal axes of sensitivity. The accelerometer structure is based on the SUMMiT V fabrication process. A set of fixed electrodes provides reliable measurements of capacitance in the two orthogonal directions. An analytical model based on the Euler-Bernoulli stress theory is introduced for variable cross-sectional area beams and is validated with a finite element analysis. In order to avoid a short circuit between fixed and movable electrodes, four displacement limiters were designed. The displacement limiters prevent out-of-plane displacement of the seismic mass and can withstand an impact of 250,000 G. A two-dimensional transient analysis of the seismic mass was carried out to confirm a linear oscillation behavior for either direction on the operation plane. The natural frequencies in the vibration modes of the two axes of interest are 462.5 and 463.2 Hz. It is also shown that the principal stresses in the beams are smaller than the fracture strength of polysilicon.