Office of Technology Transfer – University of Michigan

A Folded-Electrode Structure for Electromechanical Capacitive Accelerometers

Technology #1644

Background

Accelerometers are often utilized in various applications including navigation, guidance, microgravity measurements, seismology and platform stabilization. Conventional accelerometers are fabricated by either surface- or bulk-micromachining. The surface-micromachined devices are fabricated on a single silicon wafer, but bear low sensitivity and large noise floor. Some high resolution accelerometers are bulk-micromachined, with multiple wafer bonding as part of their manufacturing process. This bonding procedure is not only a complex fabrication step, but restrains the formation of damping holes, requiring special packaging to control the device damping factor. In addition, wafer bonding process may result in higher temperature sensitivity and larger drift of the accelerometers.

Technology

Researchers at the University of Michigan have developed a new structure for electromechanical capacitive accelerometer which enhances its performance by achieving high device sensitivity, low noise floor, and controllable damping. The invention is achieved by fabricating steps on a single-side of a single silicon wafer, while at the same time utilizing the whole wafer thickness to attain a large silicon proof mass. The “folded-electrode” structure allows of accelerometers with thick, large proof mass and thin stiff electrodes on only one side of a silicon wafer. By incorporating damping holes in the electrodes, squeeze film damping can be controlled and reduced.

Applications and Advantages

Applications

  • navigation/ guidance
  • microgravity measurements
  • seismology
  • platform stabilization
  • medical devices

Advantages

  • high device sensitivity
  • reduced mechanical noise floor
  • manufacture on a single-side of a semiconductor wafer