Single-side microelectromechanical capacitive accelerometer and method of making same

US6167757A · kind A · utility

Assignee

• THE REGENTS OF THE UNIVERSITY OF MICHIGAN · US

Inventors

• Navid Yazdi · Ann Arbor, US
• Khalil Najafi · Ann Arbor, US

Key dates

• Filing date: Aug 31, 1999
• Grant date: Jan 2, 2001
• Expiry date: Aug 31, 2019

Classification

• Technology area (CPC G): Physics
• CPC primary: G01P2015/0882
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A high sensitivity, Z-axis, capacitive microaccelerometer having stiff sense/feedback electrodes and a method of its manufacture on a single-side of a semiconductor wafer are provided. The microaccelerometer is manufactured out of a single silicon wafer and has a silicon-wafer-thick proof mass, small and controllable damping, large capacitance variation and can be operated in a force-rebalanced control loop. One of the electrodes moves with the proof mass relative to the other electrode which is fixed. The multiple, stiffened electrodes have embedded therein damping holes to facilitate force-rebalanced operation of the device and to control the damping factor. Using the whole silicon wafer to form the thick large proof mass and using thin sacrificial layers to form narrow uniform capacitor air gaps over large areas provide large capacitance sensitivity. The manufacturing process is simple and thus results in low cost and high yield manufacturing. In one preferred embodiment, the fixed electrode includes a plurality of co-planar, electrically-isolated, conductive electrodes formed by thin polysilicon deposition with embedded vertical stiffeners. The vertical stiffeners are formed by…