Microelectromechanical capactive accelerometer and method of making same

US6402968B1 · kind B1 · utility

Inventors

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

Key dates

• Filing date: Jan 12, 2000
• Grant date: Jun 11, 2002
• Expiry date: Jan 12, 2020

Classification

• Technology area (CPC G): Physics
• CPC primary: G01P15/0802
• 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 are provided. The microaccelerometer is manufactured out of a single silicon wafer and has a silicon-wafer-thick proofmass, small and controllable damping, large capacitance variation and can be operated in a force-rebalanced control loop. The multiple stiffened electrodes have embedded therein damping holes to facilitate both force-rebalanced operation of the device and controlling of the damping factor. Using the whole silicon wafer to form the thick large proofmass and using the thin sacrificial layer to form a narrow uniform capacitor air gap over a large area provide large capacitance sensitivity. The structure of the microaccelerometer is symmetric and thus results in low cross-axis sensitivity. In one embodiment, because of its all-silicon structure, the accelerometer exhibits very low temperature sensitivity and good long term stability. The manufacturing process is simple and thus results in low cost and high yield manufacturing. In the one embodiment, the electrodes are formed by thin polysilicon deposition with embedded vertical stiffeners. The …