Micro-mechanical capacitive inductive sensor for detection of relative or absolute pressure
First Claim
1. A micro-mechanical pressure transducer comprising:
- a capacitive transducer structure comprising;
a pressure sensitive diaphragm formed from a first substrate,a conductive layer formed on the diaphragm, andan electrode formed on a second substrate,an inductor coil formed within a plurality of layers forming the second substrate,the first substrate being bonded to the second substrate whereby a pre-determined air gap is formed between the diaphragm and the electrode and the capacitive transducer structure is integrated with the inductor coil to form a LC tank circuit,wherein deflections of the diaphragm in response to pressure differentials between the sealed cavity and the exterior atmosphere result in changes of capacitance between the electrode and the conductive layer on the diaphragm.
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Abstract
A micro-mechanical pressure transducer is disclosed in which a capacitive transducer structure is integrated with an inductor coil to form a LC tank circuit, resonance frequency of which may be detected remotely by imposing an electromagnetic field on the transducer. The capacitive transducer structure comprises a conductive movable diaphragm, a fixed counter electrode, and a predetermined air gap between said diaphragm and electrode. The diaphragm deflects in response to an applied pressure differential, leading to a change of capacitance in the structure and hence a shift of resonance frequency of the LC tank circuit. The resonance frequency of the LC circuit can be remotely detected by measuring and determining the corresponding peak in electromagnetic impedance of the transducer.
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Citations
31 Claims
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1. A micro-mechanical pressure transducer comprising:
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a capacitive transducer structure comprising; a pressure sensitive diaphragm formed from a first substrate, a conductive layer formed on the diaphragm, and an electrode formed on a second substrate, an inductor coil formed within a plurality of layers forming the second substrate, the first substrate being bonded to the second substrate whereby a pre-determined air gap is formed between the diaphragm and the electrode and the capacitive transducer structure is integrated with the inductor coil to form a LC tank circuit, wherein deflections of the diaphragm in response to pressure differentials between the sealed cavity and the exterior atmosphere result in changes of capacitance between the electrode and the conductive layer on the diaphragm. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A micro-mechanical pressure sensor comprising:
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a first substrate including a diaphragm, a conductive layer formed on the diaphragm, a second substrate including a plurality of layers, an inductor formed within the plurality of layers, an electrode formed on the second substrate, the first and second substrates being bonded together to form a sealed cavity between the electrode and the conductive layer formed on the diaphragm, a first via connecting the electrical inductor to the fixed electrode, and a second via connecting the electrical inductor to the conductive layer on the diaphragm, wherein deflections of the diaphragm in response to pressure differentials between the sealed cavity and the exterior atmosphere result in changes of capacitance between the electrode and the conductive layer on the diaphragm. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A micro-mechanical pressure sensor comprising:
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a first substrate including a pressure sensitive diaphragm, a conductive layer formed on the diaphragm, a second hybrid substrate including a plurality of layers, an electrical inductor formed within the plurality of layers, a fixed counter electrode formed on top of the second substrate, the first and second substrates being bonded together and hermetically sealed to form a cavity between the fixed counter electrode and the conductive layer formed on the diaphragm, whereby the counter electrode and the conductive layer formed on the diaphragm form a capacitive structure, at least one first via connecting the electrical inductor to the fixed electrode, and at least one second via connecting the electrical inductor to the conductive layer on the diaphragm, wherein deflections of the diaphragm in response to a pressure differential between the sealed cavity and the exterior atmosphere results in a change of capacitance between the fixed counter electrode and the conductive layer on the diaphragm, and wherein the capacitive structure and the electrical inductor form an LC circuit. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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Specification