Design and fabrication of single drive tri-axis MEMS gyroscope

Abstract

Gyroscopes are sensors that measure the angular rate of an rotating object along one or more coordinate axis. For measuring angular rate along all three axes, usually three different single axis gyroscopes are used. Three sensor systems imply more space and power requirements which are precious commodities in microelectronics. Single-drive tri axis gyroscopes overcome this issue. Owing to their design complications, they have not been explored to the scale of the single axis gyroscopes. In this paper we present a novel design of single drive tri-axis MEMS gyroscope with detail explanation of its working principle. Since gyroscopes are resonant sensors, the natural frequencies of drive and sense modes are expected to be as close to each other as possible to ensure maximum sensitivity. These frequencies depend on the structural dimensions of the design. A design optimization procedure using Finite Element Method (FEM) based parametric modal analysis has been suggested in order to achieve mode matching. An equivalent analytical model is also presented for drive mode and all three sense modes. The optimized design is fabricated using modified silicon on glass bulk micromachining technique. The natural frequencies in drive and sense modes of as fabricated devices were measured and compared with the numerical and analytical values, The experimental values of frequencies are well within 16% of the numerical values. A design upgrade has been suggested to further reduce this error value.