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Abstract

A pressure sensor for sensing a fluid pressure in harsh environments such as the air pressure in a tire formed on a wafer substrate. Associated circuitry deposited in CMOS layers on the wafer substrate has a conductive layer at least partially overlying the associated circuitry, the conductive layer forming a first electrode of the capacitative sensor. A conductive membrane at least partially overlies the conductive layer, and is spaced from it to form a second electrode of the capacitative sensor. The conductive membrane has one side exposed to the fluid pressure and the conductive layer is sealed from the fluid pressure by the conductive membrane such that, the associated circuitry converts the deflection of the conductive membrane into an output signal indicative of the fluid pressure. The conductive membrane is at least partially formed from a ceramic material to provide corrosion and wear resistance. Metal ceramics can be deposited as a thin membrane with sufficient flexibility for sensing pressure and are generally well suited to semiconductor fabrication processes and electrically conductive so they can be used in capacitative type pressure sensors.

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First Claim