Multiple chemically modulated capacitance determination
First Claim
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1. An apparatus for making a plurality of determinations at different sites, of an electrically conductive substance capable of modifying the capacitance of a semiconductor, comprising:
- a semiconductor;
an insulating layer, having a substantially constant predetermined capacitance and being substantially inert to said substance, said insulating layer overlaying one surface of said semiconductor at a plurality of sites;
means for retaining said electrically conductive substance in communication with at least one of said plurality of sites;
a counter electrode electrically coupled to said electrically conductive substance;
means for measuring the capacitance across said semiconductor and said insulating layer at each of said sites;
means for isolating the capacitance at each site from the capacitance at each of the other sites, wherein said means for isolating comprises a plurality of counter electrode plates, each of said plates being proximate one of said sites;
means adapted for providing high electrical impedance between said plates; and
switching means for sequentially coupling each of said plates to said capacitance measuring means.
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Abstract
Apparatus and methods are provided for multiple detection of analytes employing semiconductor capacitance as the signal modulated by the analyte. A plurality of semiconductor capacitors are organized for detection (at individual sites) of changes in capacitance which are related to changes in a fluid medium, where the change can be related to the presence of an analyte. Circuitry is designed to substantially maximize sensitivity.
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Citations
10 Claims
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1. An apparatus for making a plurality of determinations at different sites, of an electrically conductive substance capable of modifying the capacitance of a semiconductor, comprising:
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a semiconductor; an insulating layer, having a substantially constant predetermined capacitance and being substantially inert to said substance, said insulating layer overlaying one surface of said semiconductor at a plurality of sites; means for retaining said electrically conductive substance in communication with at least one of said plurality of sites; a counter electrode electrically coupled to said electrically conductive substance; means for measuring the capacitance across said semiconductor and said insulating layer at each of said sites; means for isolating the capacitance at each site from the capacitance at each of the other sites, wherein said means for isolating comprises a plurality of counter electrode plates, each of said plates being proximate one of said sites; means adapted for providing high electrical impedance between said plates; and switching means for sequentially coupling each of said plates to said capacitance measuring means. - View Dependent Claims (2, 3)
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4. An apparatus for making a plurality of determinations at different sites, of an electrically conductive substance capable of modifying the capacitance of a semiconductor, comprising:
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a semiconductor; an insulating layer, having a substantially constant predetermined capacitance and being substantially inert to said substance, said insulating layer overlaying one surface of said semiconductor at a plurality of sites; means for retaining said electrically conductive substance in communication with at least one of said plurality of sites; a counter electrode electrically coupled to said electrically conductive substance; means for measuring the capacitance across said semiconductor and said insulating layer at each of said sites; means for isolating the capacitance at each site from the capacitance at each of the other sites, wherein said means for isolating the capacitance at each site comprises a doped portion of said semiconductor proximate one of said sites, wherein an area around said doped portion is eroded to isolate said portion from other doped portions, said further comprising a plurality of insulating regions, each insulating region being between one of said doped portions and said semiconductor; means adapted for providing high electrical impedance between said plates; and switching means for sequentially coupling each of said plates to said capacitance measuring means.
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5. An apparatus for making a plurality of determinations at different sites, of an electrically conductive substance capable of modifying the capacitance of a semiconductor, comprising:
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a semiconductor; an insulating layer, having a substantially constant predetermined capacitance and being substantially inert to said substance, said insulating layer overlaying one surface of said semiconductor at a plurality of sites; means for retaining said electrically conductive substance in communication with at least one of said plurality of sites; a counter electrode electrically coupled to said electrically conductive substance; means for measuring the capacitance across said semiconductor and said insulating layer at each of said sites; means for isolating the capacitance at each site from the capacitance at each of the other sites; means adapted for providing high electrical impedance between said plates; switching means for sequentially coupling each of said plates to said capacitance measuring means; and a reference electrode electrically coupled to said electrically conductive substance.
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6. An apparatus for making a plurality of determinations at different sites, of an electrically conductive substance capable of modifying the capacitance of a semiconductor, comprising:
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a semiconductor; an insulating layer, having a substantially constant predetermined capacitance and being substantially inert to said substance, said insulating layer overlaying one surface of said semiconductor at a plurality of sites; means for retaining said electrically conductive substance in communication with at least one of said plurality of sites; a counter electrode electrically coupled to said electrically conductive substance; means for measuring the capacitance across said semiconductor and said insulating layer at each of said sites, wherein said capacitance measuring means comprises; means for providing an alternating voltage across said semiconductor and said counter electrode; and means for measuring the alternating current responsive to said alternating voltage; means for isolating the capacitance at each site from the capacitance at each of the other sites; means adapted for providing high electrical impedance between said plates; switching means for sequentially coupling each of said plates to said capacitance measuring means; and means for applying a DC bias potential across said semiconductor and counter electrode. - View Dependent Claims (7, 8)
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9. An apparatus for making a plurality of determination at different sites, of an electrically conductive substance capable of modifying the capacitance of a semiconductor, comprising:
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a monolithic semiconductor wafer; a plurality of doped regions in said semiconductor wafer, each of said regions being proximate one of said sites; an insulating layer, having a substantially constant predetermined capacitance and being substantially inert to said substance, said insulating layer overlaying said doped regions; means for retaining said electrically conductive substance in communication with at least one of said sites; a counter electrode positioned to contact said electrically conductive substance; means for measuring the capacitance across said doped regions and said insulating layer, wherein said means for measuring comprises; means for providing an alternating voltage across said semiconductor and said counter electrode; and means for measuring the alternating current responsive to said alternating voltage; means for applying a DC bias potential across said doped regions and said counter electrode; means for filtering said alternating current; means for reifying said alternating current; means for amplifying said filtered, rectified alternating current to provide a feedback signal; and means, responsive to said feedback signal, for varying said DC bias potential to maintain said alternating current constant. - View Dependent Claims (10)
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Specification