Method and apparatus for sensing radiation and providing electrical readout

Claim 2

Apparatus for sensing radiation and providing an electrical output comprising a substrate of semiconductor material of one conductivity type, an insulating member overlying a major surface of said substrate, a conducting member overlying a surface of said insulating member, a first terminal connected to said conducting member, a second terminal, and a third terminal connected to said substrate, capacitive means connected between said third and second terminals, circuit means connected between said first and second terminals for establishing a first potential at said first terminal and means for establishing a second potential at said second terminal, the difference in said first and second potentials being of a polarity and a magnitude to produce depletion of majority carriers in a region in the surface adjacent portion of said substrate underlying said conducting member, upon application of said potentials thereto, means for exposing said substrate to radiation for a period of time whereby minority carriers generated in said region and in the vicinity thereof in proportional response to the time integral of the intensity of radiation incident therein are stored in a surface adjacent layer of said region producing an inversion in conductivity thereof, circuit means for changing the potential of said first terminal to a third potential to inject minority carriers stored in said inversion layer into said substrate whereby a current flows in circuit with said substrate into said capacitive means producing a change in voltage between said second and third terminals, said change in voltage being substantially proportional to said minority carriers stored in said depletion region during said first period.

Claim 3

The combination of claim 1 in which said first terminal is returned to said first potential after a second period of time to produce a current flow in a circuit with said substrate and said capacitive means which reestablishes depletion in said region, said current flow producing a net change in voltage between said second and third terminals which is substantially proportional to the minority carriers stored in said region during said first period.

Claim 4

The combination of claim 2 in which said second period is short in relation to said first period.

Claim 5

The combination of claim 2 in which the duration of said second period is sufficiently long that charge carriers injected into said substrate during the change in potential of said conducting member from said first potential to said third potential and returned have substantially disappeared from the portion of said substrate encompassed by said region.

Claim 6

The combination of claim 1 in which said first period is short enough in respect to the radiation being sensed that the minority carriers generated by the radiation are insufficient to charge said region to its maximum capacity to store charge.

Claim 7

The combination of claim 2 in which is provided switching means for connecting said third terminal to said second terminal for a third period and for disconnecting said third terminal from said second terminal for a fourth period, said fourth period spanning said second period.

Claim 8

The combination of claim 6 in which said switching means is operated repetitively to connect and disconnect said second and third terminals and in Which the potential on said first terminal is repetitively changed from said first potential to said third potential and returned, and in which is included means for periodically sampling the voltage on said capacitive means during said fourth period and provide an electrical output varying in time in accordance with the variation in amplitude of the samples.

Claim 9

The combination of claim 2 in which said capacitive means includes a plurality of cells each including a part of said substrate of semiconductor material of one conductivity type, a part of said insulating member and a respective conducting member overlying said surface of said insulating member, and in which the conducting members of said plurality of cells are connected in circuit with said first terminal.

Claim 10

The combination of claim 2 in which said third potential is intermediate to said first and second potentials.

Claim 11

The combination of claim 2 in which said third potential is greater in absolute magnitude than the absolute magnitude of said second potential by the absolute magnitude of the threshold voltage of the structure including said substrate, said insulating member, and said conducting member.

Claim 12

The combination of claim 1 in which the capacitance of said conducting member in relation to said substrate is large in comparison to the capacitance of said region from which majority carriers are depleted immediately upon application of said first potential thereto.

Claim 13

The combination of claim 1 in which the structure including said substrate, said insulating member and said conducting member has a predetermined threshold voltage and in which the difference in potential in said first and second potentials exceeds said threshold voltage.

Claim 14

The combination of claim 1 in which the capacitance of said capacitive means is large in relation to the capacitance of said conducting member in relation to said substrate.

Claim 15

The combination of claim 1 in which said semiconductor material is silicon, said insulating member is silicon dioxide and said conducting member is a metal.

Claim 16

The combination of claim 1 in which said semiconductor material is silicon, said insulating member is silicon dioxide and said conducting member is a conductive layer of silicon.

Claim 17

In combination, a substrate of semiconductor material of one conductivity type, an insulating member overlying a surface of said substrate, a plurality of spaced conducting members overlying a surface of said insulating member, a plurality of first terminals each connected to a respective one of said conducting members, a second terminal, and a third terminal connected to said substrate, means for establishing a first potential at said first terminals, means for establishing a second potential at said second terminal, the difference in potential between said first and second potentials being of a polarity and a magnitude to deplete a plurality of regions of majority carriers in the surface adjacent portion of said substrate, each region of depletion underlying a respective conducting member, means for periodically connecting said third terminal to said second terminal during a third period of time and disconnecting said third terminal from said second terminal during a fourth period of time whereby a potential is established on said third terminal substantially equal to the potential on said second terminal during the connection thereof. means for exposing said substrate to radiation whereby minority carriers generated in each of said regions of depletion and in the vicinity thereof in proportional response to the radiation incident therein and are stored in a respective surface adjacent layer of said region producing an inversion in conductivity thereof, said first terminals being connected in turn to a third potential and back to said first potential during said fourth period to inject some of said carriers stored in a respective inversion layer into said substrate whereby a net current flows in circUit with said substrate into the capacitance provided by the other of said conducting members in relation to said substrate during said fourth period to produce a net voltage between said second and third terminals in proportional response to said injected charge. means for sampling each of said net voltages between said second and third terminals in turn to provide a time varying electrical output in accordance with the variation in amplitude of said samples.

Claim 18

In combination, a substrate of semiconductor material of one conductivity type, an insulating member overlying a surface of said substrate, a plurality of spaced conducting members overlying a surface of said insulating member, a plurality of first terminals each connected to a respective one of said conducting members, a second terminal, and a third terminal connected to said substrate, means for establishing a first potential at said first terminals, means for establishing a second potential at said second terminal, the difference in potential between said first and second potentials being of a polarity and a magnitude to deplete a plurality of regions of majority carriers in the surface adjacent portion of said substrate, each region of depletion underlying a respective conducting member, means for periodically connecting said third terminal to said second terminal during a third period of time and disconnecting said third terminal from said second terminal during a fourth period of time whereby a potential is established on said third terminal substantially equal to the potential on said second terminal during the connection thereof. means for exposing said substrate to radiation whereby minority carriers generated in each of said regions of depletion and in the vicinity thereof in proportional response to the radiation incident therein and are stored in a respective surface adjacent layer of said region producing an inversion in conductivity thereof, said first terminals being connected in turn to a third potential and back to said first potential during said fourth period to inject some of said carriers stored in a respective inversion layer into said substrate whereby a net current flows in circUit with said substrate into the capacitance provided by the other of said conducting members in relation to said substrate during said fourth period to produce a net voltage between said second and third terminals in proportional response to said injected charge. means for sampling each of said net voltages between said second and third terminals in turn to provide a time varying electrical output in accordance with the variation in amplitude of said samples.

Claim 19

In combination, a substrate of semiconductor material of one conductivity type, means including an electrode in insulated relation to a surface of said substrate and connected in a circuit with said substrate, means for applying a voltage of a polarity and magnitude between said electrode and said substrate to deplete carriers of said one conductivity type from a region adjacent said surface of the substrate whereby an initial potential is established at said surface which lies between the potential at said electrode and the potential of the substrate, and carriers of opposite conductivity type thermally generated in said region at a rate determined by the temperature of the substrate move under the influence of the electric field in said region toward the surface thereof where they accumulate in a layer adjacent said surface and cause a change in potential of said surface in the direction of the potential of the substrate, the potential of said surface attaining over a first interval of time an equilibrium value fixed in relation to the potential of the substrate, means for exposing said region to radiation of sufficient intensity to generate carriers of opposite conductivity type therein at a rate greater than said one rate of thermal generation of carriers therein whereby the equilibrium potential of said surface is attained in a second interval of time shorter than said first interval of time, means for changing the potential of said surface in the direction of the potential of said sub-strate before the end of said first interval to change the absolute magnitude of the surface potential to an extent such that some of the charge stored in said layer is unsupportable by the electric-field thereat whereby said carriers of opposite conductivity type are injected into said substrate and a current is caused to flow in said circuit, capacitive means connected in circuit with said electrode and said substrate for integrating the current flow in said circuit in response to changing the potential of said surface.

Claim 20

In combination, a substrate of semiconductor material of one conductivity type, means including an electrode in insulated relation to a surface of said substrate and connected in a circuit with said substrate, means for applying a voltage of a polarity and magnitude between said electrode and said substrate to deplete carriers of said one conductivity type from a region adjacent said surface of the substrate whereby an initial potential is established at said surface which lies between the potential at said electrode and the potential of the substrate, and carriers of opposite conductivity type thermally generated in said region at a rate determined by the temperature of the substrate move under the influence of the electric field in said region toward the surface thereof where they accumulate in a layer adjacent said surface and cause a change in potential of said surface in the direction of the potential of the substrate, the potential of said surface attaining over a first interval of time an equilibrium value fixed in relation to the potential of the substrate, means for exposing said region to radiation of sufficient intensity to generate carriers of opposite conductivity type therein at a rate greater than said one rate of thermal generation of carriers therein whereby the equilibrium potential of said surface is attained in a second interval of time shorter than said first interval of time, means for changing the potential of said surface in the direction of the potential of said sub-strate before the end of said first interval to change the absolute magnitude of the surface potential to an extent such that some of the charge stored in said layer is unsupportable by the electric-field thereat whereby said carriers of opposite conductivity type are injected into said substrate and a current is caused to flow in said circuit, capacitive means connected in circuit with said electrode and said substrate for integrating the current flow in said circuit in response to changing the potential of said surface.

Claim 21

The combination of claim 17 in which the interval of time from the application of said voltage to the changing of said voltage to inject carriers of opposite conductivity type stored in said region is substantially less than said first interval.

Claim 22

The combination of claim 17 in which the interval of time from the application of said voltage to the changing of said voltage to inject carriers of opposite conductivity type stored in said region is substantially less than said second interval.

Claim 23

The combination of claim 17 in which changing the potential of said surface is produced by changing the magnitude of said voltage to a value less than the initial value thereof and greater than the magnitude of the threshold voltage of said electrode in insulated relationship to said substrate.

Claim 24

The combination of claim 17 in which said change in potential of said surface is produced by reducing the magnitude of said voltage to zero.

Claim 25

The combination of claim 17 in which is provided means for returning the potential of said surface to its initial potential after a third interval of time from the instant of changing the potential of said surface, said third interval being of sufficient duration to allow said carriers of opposite type injected into said substrate to disappear from said region whereby a charging current flows in said circuit, and in which said means for sensing current flow includes means for integrating the charge flow in said circUit in response to the initial changing of the potential of said surface and to the returning of the potential of said surface to its initial potential whereby a net charge flow is obtained which is a measure of the radiation incident on said region from the instant of application of said voltage to the instant of changing said voltage to cause injection of said charge into said substrate.

Claim 26

The combination of claim 22 in which said integrating means is a capacitor connected in said circuit during said other interval, whereby a voltage is developed across said capacitor corresponding to said net flow of charge in said circuit.

Claim 27

A radiation sensing device comprising a substrate of semiconductor material of one conductivity type having a major surface, a conducting member overlying a portion of a region of said substrate adjacent said major surface and in insulating relationship therewith, a voltage means for providing a voltage between said conducting member and said substrate to deplete said portion of majority charge carriers, means for exposing said substrate to radiation whereby minority carriers generated in said portion are stored therein, means for collapsing said voltage whereby charge stored in said second portion is injected into said substrate, capacitive means in circuit with said substrate and said conductive member for integrating the charge injected into said substrate.

Claim 28

A radiation sensing device comprising a substrate of semiconductor material of one conductivity type having a major surface, a conducting member overlying a portion of a region of said substrate adjacent said major surface and in insulating relationship therewith, a voltage means for providing a voltage between said conducting member and said substrate to deplete said portion of majority charge carriers, means for exposing said substrate to radiation whereby minority carriers generated in said portion are stored therein, means for collapsing said voltage whereby charge stored in said second portion is injected into said substrate, capacitive means in circuit with said substrate and said conductive member for integrating the charge injected into said substrate.

Claim 29

A radiation sensing device comprising a substrate of semiconductor material of one conductivity type having a major surface, a plurality of conducting members, each overlying a respective portion of a region of said substrate adjacent said major surface and in insulating relationship therewith, said voltage means providing a voltage between said conducting members and said substrate to deplete said portions of majority charge carriers, means for exposing said substrate to radiation whereby minority carriers generated in said portions are stored therein, means for collapsing and reestablishing said voltage on each of said conducting members in sequence whereby charge stored in each of said portions of said surface adjacent region is injected in turn into said substrate, capacitive means in circuit with said substrate and said conductive members for integrating in turn the charge injected into said substrate.

Claim 30

A radiation sensing device comprising a substrate of semiconductor material of one conductivity type having a major surface, a plurality of conducting members, each overlying a respective portion of a region of said substrate adjacent said major surface and in insulating relationship therewith, said voltage means providing a voltage between said conducting members and said substrate to deplete said portions of majority charge carriers, means for exposing said substrate to radiation whereby minority carriers generated in said portions are stored therein, means for collapsing and reestablishing said voltage on each of said conducting members in sequence whereby charge stored in each of said portions of said surface adjacent region is injected in turn into said substrate, capacitive means in circuit with said substrate and said conductive members for integrating in turn the charge injected into said substrate.