Organic semiconductor sensor device

• US 20040056245A1
• Filed: 09/25/2002
• Published: 03/25/2004
• Est. Priority Date: 09/25/2002
• Status: Active Grant

• Current Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Thomas, Danielle A., Thoma, Peter J., Debeurre, Bruno J.
• Granted Patent: US 6,852,996 B2
• Time in Patent Office: Days
• US Class Current: 257/40
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence
• CPC Class Codes: G01L 1/148 using semiconductive material, e.g. silicon
• CPC Class Codes: G01N 27/4145 specially adapted for biomolecules, e.g. gate electrode with immobilised receptors
• CPC Class Codes: G01N 27/4148 Integrated circuits therefor, e.g. fabricated by CMOS processing CMOS processing per se H01L21/82
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: H10K 10/46 Field-effect transistors, e.g. organic thin-film transistors [OTFT] H10K10/43 takes precedence
• CPC Class Codes: H10K 39/32 Organic image sensors

Abstract

Sensor cells are arranged in an array in an organic semiconductor layer. Row and column select circuitry addresses the cells of the array one cell at a time to determine the presence of an object, such as a fingerprint ridge or valley, contacting or proximate to a sensing surface above each cell. Control circuitry can be provided in a companion silicon chip or in a second layer of organic semiconductor material to communicate with the array and an associated system processor. The array of sensor cells can be fabricated using a flexible polymer substrate that is peeled off and disposed of after contacts have been patterned on the organic semiconductor layer. The organic semiconductor layer can be used with a superimposed reactive interface layer to detect specific chemical substances in a test medium.

Claims

1. A sensor, comprising:

an organic semiconductor layer having a sensing surface, the layer comprising material having majority mobile charge carriers of a first conductivity type distributed throughout a region beneath the sensing surface;

a first conductive plate spaced from the sensing surface;

a second conductive plate spaced from the sensing surface and from the first conductive plate; and

a gate electrode interposed between the first and second conductive plates, the gate electrode introducing a depletion region in the organic semiconductor layer beneath the sensing surface in response to a voltage bias applied to the gate electrode, a dimension of the depletion region varying in response to the presence of an object proximate to the sensing surface, the variation in the dimension being detectable by sensing a signal communicated through the organic semiconductor layer below the sensing surface.

2. The sensor of claim 1 wherein the first conductivity type is p-type characterized by a uniform distribution of positive majority mobile charge carriers in an unbiased state.

3. The sensor of claim 1 wherein the organic semiconductor layer has a non-uniform distribution of p-type conductivity material, the layer including a relatively thick upper portion having a light concentration of p-type material extending downward from the sensing surface and a relatively thin lower portion having a heavy concentration of p-type material extending downward from the relatively thick upper portion to a lower surface of the layer opposite from the sensing surface.

4. An organic semiconductor device, comprising:

an organic semiconductor layer having upper and lower planar surfaces spaced apart in parallel planes defining the thickness of the layer; and

a pattern of conductors on the lower surface defining an array of sensor cells arranged in rows and columns, the conductors at each cell location including first and second plates and a gate between the plates, the gate of each cell introducing a depletion region in the organic semiconductor layer in response to a voltage bias applied to all gates of one selected column, the depletion region extending upward from the lower surface, a dimension of the depletion region in the direction perpendicular to the parallel planes varying in response to the presence of an object proximate to the upper surface, the degree of variation of the dimension being detectable by sensing a signal communicated through the organic semiconductor layer below the upper surface of the layer, the signal being communicated through the cells of one selected row, only one cell of the array corresponding to the selected column and selected row being sensed at a time.

5. The organic semiconductor device of claim 4 wherein the organic semiconductor layer comprises p-type conductivity material, characterized by a uniform distribution of positive majority mobile charge carriers above the plates of each sensor cell when the layer is in an unbiased state.

6. The organic semiconductor device of claim 4 further comprising:

a control unit;

column select circuitry operating in response to the control unit for connecting only the cells of the selected column to a voltage source to introduce depletion regions above the gates of the cells of the selected column; and

row select circuitry operating in response to the control unit for connecting only the selected row to the control unit for sensing the signal communicated through the selected row.

7. The organic semiconductor device of claim 6, further comprising:

a pulse generator connected to the rows operating under the control of the control unit for generating the signal that is communicated through the selected row; and

a load element for each column connecting the column to a ground connection causing the gates of the cells of the non-selected columns to be discharged to ground while the gates of the cells of the selected column are energized by the voltage source.

8. A fingerprint detector, comprising:

an organic semiconductor layer having an array of sensor cells formed therein, the layer having an upper sensing surface and conductors on a lower surface;

a substrate on which the organic semiconductor layer is mounted, the substrate having an upper surface with contacts thereon; and

a silicon semiconductor chip supported proximate to the organic semiconductor layer and in electrical communication therewith;

wherein selected contacts on the upper surface of the substrate are connected to the conductors on the lower surface of the organic semiconductor layer.

9. The fingerprint detector of claim 8 wherein the organic semiconductor layer includes a grounded grid disposed therein at the sensing surface.

10. The fingerprint detector of claim 9 further comprising a frame at the peripheral edges of the organic semiconductor layer for securing the layer to the substrate and providing a connection to the grid.

11. The fingerprint detector of claim 8 wherein the silicon semiconductor chip is mounted on the upper surface of the substrate.

12. The fingerprint detector of claim 8 further comprising:

a second substrate disposed beneath the substrate on which the organic semiconductor layer is mounted; and

an annular support mounted on the second substrate and securing the two substrates together, the annular support having an interior cavity that contains the silicon semiconductor chip, the silicon semiconductor chip being mounted on the second substrate beneath the organic semiconductor layer.

13. A method of making a sensor device, comprising:

providing a flexible polymer substrate;

forming a peelable film on an upper surface of the flexible polymer substrate;

forming an organic semiconductor layer atop the peelable film, the layer having an exposed major surface opposite the peelable film;

creating a pattern of conductors atop the exposed major surface of the organic semiconductor layer;

providing a permanent substrate with contacts on an upper surface thereof;

mounting the organic semiconductor layer with the flexible polymer substrate secured thereto by the peelable film on the permanent substrate oriented so that selected conductors of the pattern of conductors on the organic semiconductor layer make contact with the contacts on the upper surface of the permanent substrate; and

removing the flexible polymer substrate with the peelable film adhered thereto from the organic semiconductor layer.

14. A sensor device, comprising:

a substrate having an upper surface with contacts thereon;

a lower organic semiconductor layer mounted on the upper surface of the substrate and electrically interconnected therewith, the lower organic semiconductor layer including regions of n-type and p-type conductivity therein defining control circuitry; and

an upper organic semiconductor layer mounted above the lower organic semiconductor layer and electrically interconnected therewith, the upper organic semiconductor layer including an array of sensor cells therein.

15. The sensor device of claim 14 wherein the upper organic semiconductor layer is characterized by p-type conductivity material throughout the upper organic semiconductor layer.

16. The sensor device of claim 14 wherein the array of sensor cells are adapted to sense the presence of the skin of a human finger in contact with a sensing surface of the upper organic semiconductor layer, the sensor cells being capable of distinguishing a fingerprint ridge from a fingerprint valley thereabove.

17. The sensor device of claim 14 wherein each sensor cell is structured to provide a junction field-effect transistor thereat, the transistor having source and drain contacts and a gate electrode therebetween, the gate electrode being selectively energizable to cause the sensor cell to operate in a sensing mode when the gate electrode is energized, each sensor cell having a JFET channel in the sensing mode, wherein the JFET channel has a capacitance that varies with the presence or absence of an object proximate to a surface portion of the upper organic semiconductor layer directly above each sensor cell.

18. A sensor device, comprising:

a substrate having an upper surface with contacts thereon;

an organic semiconductor layer supported above the substrate, the organic semiconductor layer including a sensor cell therein; and

a reactive interface layer disposed on the organic semiconductor layer, the reactive interface layer having an exposed upper surface, the reactive interface layer comprising a polymer containing a chemical that is selectively reactive to a specific substance in contact with the exposed upper surface;

wherein a reaction in the reactive interface layer of the chemical therein with the specific substance is sensed by the sensor cell in the organic semiconductor layer, whereby the sensor device can detect exposure to the specific substance.

19. The sensor device of claim 18 wherein the chemical is an enzyme.

20. The sensor device of claim 19 wherein the enzyme is glucose oxidase and the specific substance is glucose.