A planar, x-axis, single-crystalline silicon gyroscope fabricated using the extended SBM process

A planar, x-axis, single-crystalline silicon gyroscope is fabricated using one (111) SOI wafer using the extended SBM (sacrificial bulk micromachining) process. The gyroscope uses vertically offset combs to resonate the proof mass in the vertical plane, and lateral combs to sense the Coriolis force in the horizontal plane. The extended SBM process is a simple two-mask process, and because all structural parts and combs are defined in one mask level, there is no misalignment in any structural parts or comb fingers. Furthermore, all vertical dimensions of the structure, including the comb height, comb offset and sacrificial gap, can be defined arbitrarily. In addition, the inherent footing phenomenon in the SOI deep etching is completely eliminated and smooth structural shapes are obtained. The fabricated x-axis gyroscope can resolve 0.1 deg/sec angular rate, and the measured bandwidth is 100 Hz. The reported work represents the first x-axis single-crystalline silicon gyroscope fabricated using only one wafer without wafer bonding. In this paper, SOI wafer was used for electrical isolation, but the same device can be fabricated using other available electrical isolation techniques using only one ordinary (111) wafer, albeit fabrication processes are more complicated.