All-silicon capacitive pressure sensor
First Claim
1. A capacitive pressure sensor comprising:
- a semiconductor wafer, at least a portion of the semiconductor wafer being characterized by a first electrical conductivity type;
a doped region of the first electrical conductivity type in a surface of the semiconductor wafer, the doped region being a fixed capacitor plate of the capacitive pressure sensor; and
a diaphragm bonded to the semiconductor wafer such that the diaphragm overlies the fixed capacitor plate and forms a hermetic seal around the fixed capacitor plate, the diaphragm being of the first electrical conductivity type and electrically insulated from the fixed capacitor plates, the diaphragm being a flexible capacitor plate of the capacitive pressure sensor;
wherein the flexible capacitor plate forms a gap with the fixed capacitor plate of up to about ten micrometers, and a capacitive output signal of the capacitive pressure sensor is produced by changes in contact area between the diaphragm and the semiconductor wafer in response to pressure applied to the diaphragm.
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Accused Products
Abstract
An all-silicon monolithic capacitive absolute pressure-sensing device and method for making the same. The device employs a single-crystal silicon diaphragm that serves at a flexible capacitor plate of a variable capacitor. The diaphragm is bonded to a single-crystal silicon wafer to overlie a cavity etched into the wafer. A fixed capacitor plate of the variable capacitor is formed by a heavily-doped region at the bottom of the cavity. A thin dielectric layer is grown on the fixed capacitor plate to complete the capacitor. The cavity has a minimal depth such that the fixed capacitor plate provides overpressure protection for the diaphragm. At least a portion of the operating range of the pressure sensor occurs while the diaphragm is contacting the doped region. As a result, the capacitive output signal of the pressure sensor is produced by changes in contact area between the diaphragm and a thin dielectric situated on the doped region in response to pressure applied to the diaphragm.
61 Citations
8 Claims
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1. A capacitive pressure sensor comprising:
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a semiconductor wafer, at least a portion of the semiconductor wafer being characterized by a first electrical conductivity type; a doped region of the first electrical conductivity type in a surface of the semiconductor wafer, the doped region being a fixed capacitor plate of the capacitive pressure sensor; and a diaphragm bonded to the semiconductor wafer such that the diaphragm overlies the fixed capacitor plate and forms a hermetic seal around the fixed capacitor plate, the diaphragm being of the first electrical conductivity type and electrically insulated from the fixed capacitor plates, the diaphragm being a flexible capacitor plate of the capacitive pressure sensor; wherein the flexible capacitor plate forms a gap with the fixed capacitor plate of up to about ten micrometers, and a capacitive output signal of the capacitive pressure sensor is produced by changes in contact area between the diaphragm and the semiconductor wafer in response to pressure applied to the diaphragm. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification