Excitation of polysilicon based piezoresistive pressure sensors
First Claim
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1. A semiconductor sensor comprising:
- a) an impedance circuit comprising at least one piezoresistor element formed on a semiconductor diaphragm to which a pressure to be detected is applied, said impedance circuit having a first input terminal and a second input terminal and first and second output terminal;
b) means for applying an alternating differential excitation source across said first input terminal and said second input terminal of said impedance circuit for electrically powering said at least one piezoresistor element; and
c) means for measuring voltages across said output terminals when said excitation source is at alternate phases, and means for using said measured voltages to determine said pressure.
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Abstract
A polycrystalline pressure sensor is formed by depositing polycrystalline silicon piezoresistors on a polycrystalline sensing diaphragm. The piezoresistors are arranged in a wheatstone bridge configuration. During operation, an alternating differential signal is applied across the input of the wheatstone bridge. A measured voltage difference between the output terminals of the wheatstone bridge is used to detect imbalance in the electrical piezoresistors that corresponds to pressure applied to the sensor. Pressure is thereby measured.
38 Citations
24 Claims
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1. A semiconductor sensor comprising:
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a) an impedance circuit comprising at least one piezoresistor element formed on a semiconductor diaphragm to which a pressure to be detected is applied, said impedance circuit having a first input terminal and a second input terminal and first and second output terminal; b) means for applying an alternating differential excitation source across said first input terminal and said second input terminal of said impedance circuit for electrically powering said at least one piezoresistor element; and c) means for measuring voltages across said output terminals when said excitation source is at alternate phases, and means for using said measured voltages to determine said pressure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for calculating the resistance of a polysilicon pressure sensor, the method comprising the steps of:
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a) applying a first differential voltage into the sensor, the first voltage having an alternating voltage waveform of an amplitude of less than 10 volts and a frequency of less than 100 k Hz; b) measuring a first voltage level across the sensor when the first voltage is present; c) applying a second differential voltage into the sensor, the second voltage being identical to the first voltage but out of phase therewith; d) measuring a second voltage level across the sensor when the second voltage is present; and e) calculating the resistance of the sensor as a function of the measured first voltage level and the measured second voltage level.
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12. A semiconductor sensor comprising:
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a) a polysilicon sensing diaphragm for deflecting due to a pressure applied thereto; b) at least one polysilicon piezoresistor sensing element deposited onto said polysilicon sensing diaphragm for detecting the applied pressure, said at least one polysilicon piezoresistor sensing element having a first input terminal and a second input terminal and a pair of output terminals; c) a dielectric layer interposed between said polysilicon sensing diaphragm and said at least one polysilicon piezoresistor sensing element for providing electrical isolation; d) an excitation source connected across said first input terminal and said second input terminal for electrically powering said at least one polysilicon piezoresistor sensing element, said excitation source providing differential AC excitation; and e) a measuring circuit, synchronized with said excitation source, for measuring voltages across said output terminals during opposite phases of said excitation source. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A driving apparatus for operating a semiconductor sensor, said semiconductor sensor comprising at least one piezoresistor element and having a first input terminal and a second input terminal, said driving apparatus comprising:
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a first output, said first output electrically coupled to said first input terminal; a second output, said second output electrically coupled to said second input terminal; and a driver circuit electrically coupled to said first output and said second output, said driver circuit selectively operable to alternately engage one of a first voltage and a second voltage on said first output and the other of said first voltage and said second voltage on said second output, wherein said first voltage is different from said second voltage. - View Dependent Claims (20, 21)
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22. A method for operating a semiconductor sensor, said semiconductor sensor comprising at least one piezoresistor element and having a first input terminal and a second input terminal and an output, said method comprising:
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(a) alternately engaging one of a first voltage and a second voltage on said first input terminal of said semiconductor sensor; (b) alternately engaging the other of said first voltage and said second voltage on said second input terminal of said semiconductor sensor, wherein said first voltage is different from said second voltage; and (c) in synchronization with said steps (a) and (b), measuring voltages at said output. - View Dependent Claims (23, 24)
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Specification