A Bulk Micromachined Si-on-Glass Tunneling Accelerometer

A bulk micromachined tunneling accelerometer on Pyrex 7740 substrate is reported in this paper, which is intended for the applications in highly sensitive inertia measurements, such as those in microgravity environments and self-contained navigation. The tunneling tip is defined by an isotropic wet etching followed by a maskless wet thermal oxidation for the sharpening of the tip. Unlike the process ever reported by other facilities, an ICP etching on the side of the Si wafer with the tip is utilized to partially define the suspension and the proof mass before the anodic bonding of the Si wafer with the glass substrate, and an addition maskless ICP etching is used to release the whole movable structure after the bonding. Fabricated samples have displayed the effectiveness of the process proposed, which is relatively simple and may guarantee the yield of mass production. The theoretical analysis and design of the closed loop architecture of the device are demonstrated. Capable of sensing out-of-plane acceleration, this device has demonstrated a high resolution of 0.015mg/rtHz (@ 1∼100Hz) and a nonlinearity of less than 1% over ±1g input range.