Parameter design of triaxial microaccelerometers with piezoelectric thin-film

This study proposes an analytical model for a high sensitivity piezoelectric thin film triaxial microaccelerometer, and investigates the influence of the fabrication processes on the parameter design. The structure design is consisted of four parallel suspension beams, a central seismic mass, and eight piezoelectric thin film transducers. The sensitivity consistence between out-of-plane and in-plane accelerations is a key issue for the following signal processing. A simplified system modeling scheme based on anisotropic material properties using area moment method and laminated beam theory is presented and applied to the parameter design. An optimized thickness ratio between piezoelectric thin film and the silicon substrate of the laminated supporting beam is derived to maximize the sensitivity. The study shows that the aspect ratio of the seismic mass is the deterministic factor to the differences among triaxial sensitivities. The triaxial sensitivity performances for two structure designs with the seismic masses fabricated using chemical wet etching and deep reactive ion etching (DRIE) are compared. The design using DRIE provides more even triaxial sensitivity, while the design using wet etching shows cost advantage with additional parameter constraints due to the required compensation pattern for convex corner etching.