Silicon resonant strain gauges fabricated using SOI wafers

This paper details the design and fabrication process for a dynamically balanced silicon resonator. To optimise the degree of dynamic balance extensive finite element modelling (FEM) of the mechanical structure was carried out. A method of driving and detecting the optimum mode of the resonator was chosen in order to avoid compromising the mechanical design of the structure. The degree of dynamic balance has important implications for the use of the resonator in strain sensing applications. In the fabrication process silicon-on-insulator (SOI) wafers are used that enable the manufacture of the resonator in single-crystal silicon. This is an ideal mechanical material for such an application and is mechanically superior to polysilicon with wholly repeatable material properties. The fabrication process described in this paper has been designed to be relatively straightforward, thereby enabling the application of resonant strain gauges to a wide range of devices.