Organic semiconductor sensor device

• US 6,852,996 B2
• Filed: 09/25/2002
• Issued: 02/08/2005
• Est. Priority Date: 09/25/2002
• Status: Expired due to Term

• Current Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Thomas, Danielle A., Thoma, Peter J., Debeurre, Bruno J.
• Primary Examiner(s): Thomas, Tom
• Assistant Examiner(s): LANDAU, MATTHEW C
• Application Number:
  US10/254,311
• Publication Number:
  US 20040056245A1
• Time in Patent Office: 867 Days
• Field of Search: 257/40, 257/252, 257/253, 257/414, 324/686
• 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 on one side and a contact surface on the side of the layer opposite from the 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 organic semiconductor layer being so constructed that a depletion region will be formed therein 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 from the first conductive plate to the second conductive plate through the organic semiconductor layer below the sensing surface;

wherein the first conductive plate, the second conductive plate, and the gate electrode are each disposed in contact with the contact surface.

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

3. 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;

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;

wherein the organic semiconductor layer includes a grounded grid disposed therein at the sensing surface; and

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.