Multiple chemically modulated capacitance determination

Claim 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.

Claim 2

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.

Claim 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: 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.

Claim 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: 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.

Claim 7

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; 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.

Claim 8

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; 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.

Claim 9

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, 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.

Claim 10

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, 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.

Claim 13

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: 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.

Claim 14

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: 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.