Pressure sensor with apertured membrane guard
First Claim
1. A pressure sensor for sensing a fluid pressure, the pressure sensor comprising:
- a wafer substrate with a recess;
a flexible membrane covering the recess to define a chamber containing a fluid at a reference pressure, such that the flexible membrane deflects due to pressure differentials between the reference pressure and the fluid pressure;
associated circuitry for converting the deflection of the flexible membrane into an output signal indicative of the fluid pressure; and
, an apertured guard over the membrane formed using lithographically masked etching and deposition techniques.
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Accused Products
Abstract
A pressure sensor (30) for harsh environments such as vehicle tires, formed from a wafer substrate (32) with a recess, a flexible membrane (50) covering the recess to define a chamber (58) containing a fluid at a reference pressure. In use, the flexible membrane (50) deflects due to pressure differentials between the reference pressure and the fluid pressure. Associated circuitry (34) converts the deflection of the flexible membrane (50) into an output signal indicative of the fluid pressure. An apertured guard (54) over the membrane formed using lithographically masked etching and deposition techniques protects the delicate MEMS structures. Forming the guard in situ by depositing material offers greater time efficiency and accuracy than producing a guard separately and securing it over the membrane. Semiconductor etching and deposition techniques allow highly intricate surface details. The apertures in the guard can be made smaller to exclude more particles from contacting the membrane. The fine tolerances of lithographic deposition permit the guard to be positioned close to the membrane for a more compact overall design.
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Citations
46 Claims
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1. A pressure sensor for sensing a fluid pressure, the pressure sensor comprising:
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a wafer substrate with a recess;
a flexible membrane covering the recess to define a chamber containing a fluid at a reference pressure, such that the flexible membrane deflects due to pressure differentials between the reference pressure and the fluid pressure;
associated circuitry for converting the deflection of the flexible membrane into an output signal indicative of the fluid pressure; and
,an apertured guard over the membrane formed using lithographically masked etching and deposition techniques. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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44. A method of fabricating pressure sensor for sensing a fluid pressure, the method of fabrication comprising:
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sequential etching and deposition of material on a wafer substrate to form a chamber at least partially defined by a flexible membrane;
such that,during use the chamber contains a fluid at a reference pressure and the flexible membrane deflects from a pressure difference between the reference pressure and the fluid pressure;
depositing associated circuitry for converting the deflection of the flexible membrane into an output signal indicative of the fluid pressure; and
,depositing an apertured guard over the membrane. - View Dependent Claims (45, 46)
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Specification