CDS capable sensor with photon sensing layer on active pixel circuit

• US 20070285545A1
• Filed: 08/17/2007
• Published: 12/13/2007
• Est. Priority Date: 08/27/2002
• Status: Active Grant

• Current Assignee: E-Phocus Corp.
• Original Assignee: E-Phocus Corp.
• Inventors: Hsieh, Tzu-Chiang
• Granted Patent: US 7,786,543 B2
• Time in Patent Office: Days
• US Class Current: 348/294
• CPC Class Codes: H01L 27/14634 Assemblies, i.e. Hybrid structures
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H04N 25/616 involving a correlated sampling function, e.g. correlated double sampling [CDS] or triple sampling
• CPC Class Codes: H04N 25/778 comprising amplifiers shared between a plurality of pixels, i.e. at least one part of the amplifier must be on the sensor array itself
• CPC Class Codes: H04N 5/32 Transforming X-rays cameras or camera modules for generating image signals from X-rays H04N23/30; circuitry of SSIS for transforming X-rays into image signals H04N25/30

Abstract

A MOS or CMOS based active pixel sensor with special sampling features to substantially eliminate clock noise. The sensor includes an array of pixels fabricated in or on a substrate, each pixel defining a charge collection node on which charges generated inside a photodiode region are collected, a charge integration node, at which charges generated in said pixel are integrated to produce pixel signals, a charge sensing node from which reset signals and the pixel signals are sensed. In preferred embodiments the sensor includes a continuous electromagnetic radiation detection structure located above the pixel circuits providing a photodiode region for each pixel. The sensor includes integrated circuit elements adapted to maintain voltage potentials of the charge integration nodes substantially constant during charge integration cycles. The sensor also includes integrated circuit elements having electrical capacitance adapted to store charges providing an electrical potential at the charge integration node. In preferred embodiments this is a pinned diode.

Claims

1. A MOS or CMOS based active pixel sensor comprising:

A) a substrate;

B) an array of pixels fabricated in or on said substrate, each pixel comprising a plurality of integrated circuits defining;

1) a charge collection node on which charges generated inside the photodiode are collected,

2) a charge integration node, at which charges generated in said pixel are integrated to produce pixel signals,

3) a charge sensing node from which reset signals and the pixel signals are sensed;

C) an electromagnetic radiation detection structure located above said pixel circuits for converting electromagnetic radiation into charges during charge integration cycles, said electromagnetic detection structure defining a photodiode region for each of said pixels, comprising;

1) a pixel electrode for each pixel,

2) at least one layer of charge generating material to generate charges upon the absorption of electromagnetic radiation, and

3) a surface electrode in the form of a thin transparent layer or grid located above said layers of charge generating material;

wherein said plurality of integrated circuits of each of said pixels comprises;

1) integrated circuit elements adapted to maintain voltage potentials of said charge collection nodes substantially constant during charge integration cycles,

2) integrated circuit elements having electrical capacitance adapted to store charges providing an electrical potential at said charge integration node,

3) integrated circuit elements adapted to control the transfer of charges from the charge integration node to the charge sensing node,

4) integrated circuit elements having electrical capacitance adapted to store charges providing an electrical potential at said charge sensing node,

5) integrated circuit elements adapted to reset said charge sensing node,

6) integrated circuit elements adapted to convert the charges on the charge sensing node into electrical signal, and

7) integrated circuit elements adapted to readout electrical signals generated in said pixels.

2. The sensor as in claim 1 wherein said at least on layer of charge generating material is comprised of an n-doped amorphous silicon, an intrinsic amorphous layer, and a p-doped amorphous silicon layer.

3. The sensor as in claim 2 said surface electrode is a continuous layer comprised of indium tin oxide.

4. The sensor as in claim 3 wherein said pixel electrode is a metalized region in electrical communication with pixel circuit elements.

5. The sensor as in claim 1 wherein said integrated circuit elements adapted to maintain voltage potentials of said charge collection nodes substantially constant during charge integration cycles comprise a constant bias transistor.

6. The sensor as in claim 1 integrated circuit elements having electrical capacitance adapted to store charges providing an electrical potential at said charge integration node is a first diode.

7. The sensor as in claim 6 wherein said first diode is a pinned diode,

8. The sensor as in claim 1 wherein said integrated circuit elements adapted to control the transfer of charges from the charge integration node to the charge sensing node comprise a transistor.

9. The sensor as in claim 1 integrated circuit elements having electrical capacitance adapted to store charges providing an electrical potential at said charge sensing node is a second diode.

10. The sensor as in claim 1 wherein said integrated circuit elements adapted to reset said charge sensing node comprise a transistor.

11. The sensor as in claim 1 wherein said integrated circuit elements adapted to convert the charges on the charge sensing node into electrical signal comprise a source follower transistor.

12. The sensor as in claim 1 wherein said integrated circuit elements adapted to readout signals electrical signals generated in said pixels comprise a row select transistor.

13. The sensor as in claim 1 wherein said integrated circuit elements adapted to reset said charge sensing node is also adapted to permit reset said charge integration node.

14. The sensor as in claim 1 wherein said sensor is comprised of additional integrated circuit elements adapted to permit correlated double sampling.

15. The sensor as in claim 7 wherein said substrate is doped with a dopant of a first kind to define a first doped region with a first doping concentration.

16. The sensor as in claim 15 wherein said pinned diode is further comprised of a second doped region of a dopant of a second kind inside the said first doped region and a third doped region of dopant of said first kind inside the said second doped region and adjacent to an interface between said substrate and its above dielectric layer and having a doping concentration higher than said first doping concentration.

17. The sensor as in claim 16 wherein said interface is an interface between a silicon substrate and an insulating dielectric layer.

18. The sensor as in claim 1 wherein said substrate comprises an upper epitaxial layer.

23. The sensor as in claim 1 wherein said radiation detection structure is comprised of a plurality of photon sensing layers deposited over said array of active pixels.

24. The sensor as in claim 1 wherein said radiation detection structure is comprised of a separately fabricated structure that is bonded to said array of active pixels.

31. The sensor as in claim 1 wherein said electrical capacitance of said integrated circuit elements adapted to store charges is further comprised of conductor-insulator type capacitance.

19. A MOS or CMOS based active pixel sensor comprising:

A) a substrate;

B) an array of pixels fabricated in or on said substrate, each pixel comprising a plurality of integrated circuits defining;

1) a charge collection node on which charges generated inside the photodiode are collected,

2) a charge integration node, at which charges generated in said pixel are integrated to produce pixel signals,

3) a charge sensing node from which reset signals and the pixel signals are sensed;

C) an array of pixel readout circuits fabricated in or on said substrate, each pixel readout circuits comprising a plurality of integrated circuits defining a charge sensing node from which reset signals and the pixel signals are sensed;

D) an electromagnetic radiation detection structure located above said pixel circuits for converting electromagnetic radiation into charges during charge integration cycles, said electromagnetic detection structure defining a photodiode region for each of said pixels, comprising;

1) pixel electrode for each pixel,

2) at least one layer of charge generating material to generate charges upon the absorption of electromagnetic radiation, and

3) a surface electrode in the form of a thin transparent layer or grid located above said layers of charge generating material;

wherein said plurality of integrated circuits of each of said pixels comprises;

1) integrated circuit elements adapted to maintain voltage potentials of said charge collection nodes substantially constant during charge integration cycles,

2) integrated circuit elements having electrical capacitance adapted to store charges providing an electrical potential at said charge integration node,

3) integrated circuit elements adapted to control the transfer of charges from the charge integration node to the charge sensing node,

wherein said plurality of integrated circuits of said plurality of pixel readout circuits comprises;

1) integrated circuit elements having electrical capacitance adapted to store charges providing an electrical potential at said charge sensing node,

2) integrated circuit elements adapted to reset said charge sensing node,

3) integrated circuit elements adapted to convert the charges on the charge sensing node into electrical signal, and

4) integrated circuit elements adapted to readout electrical signals generated in said pixels.

20. The sensor as in claim 19 wherein each of said plurality of pixel readout circuits is shared by a plurality of said pixel circuits.

25. The sensor as in claim 19 wherein said radiation detection structure is comprised of a plurality of photon sensing layers deposited over said array of active pixels.

26. The sensor as in claim 19 wherein said radiation detection structure is comprised of a separately fabricated structure that is bonded to said array of active pixels.

32. The sensor as in claim 19 wherein said electrical capacitance of said integrated circuit elements adapted to store charges is further comprised of conductor-insulator-conductor type capacitance.

21. A MOS or CMOS based active pixel sensor comprising:

A) a substrate;

B) an array of pixels fabricated in or on said substrate, each pixel comprising a plurality of integrated circuits defining;

1) a charge collection node on which charges generated inside the photodiode are collected,

2) a charge integration node, at which charges generated in said pixel are integrated to produce pixel signals,

3) a charge sensing node from which reset signals and the pixel signals are sensed;

C) an electromagnetic radiation detection structure located above said pixel circuits for converting electromagnetic radiation into charges during charge integration cycles, said electromagnetic detection structure defining a photodiode region for each of said pixels, comprising;

1) a pixel electrode for each pixel,

2) at least one layer of charge generating material to generate charges upon the absorption of electromagnetic radiation, and

3) a surface electrode in the form of a thin transparent layer or grid located above said layers of charge generating material;

wherein said plurality of integrated circuits of each of said pixels comprises;

1) a constant gate bias transistor adapted to maintain voltage potentials of said charge collection nodes substantially constant during charge integration cycles,

2) a pinned diode having electrical capacitance adapted to store charges providing an electrical potential at said charge integration node,

3) a transfer transistor switch adapted to control the transfer of charges from the charge integration node to the charge sensing node,

4) a diode having electrical capacitance adapted to store charges providing an electrical potential at said charge sensing node,

5) a reset transistor adapted to reset said charge sensing node,

6) a source follower transistor adapted to convert the charges on the charge sensing node into electrical signal, and

7) a row readout transistor switch adapted to readout electrical signals generated in said pixels.

27. The sensor as in claim 21 wherein said radiation detection structure is comprised of a plurality of photon sensing layers deposited over said array of active pixels.

28. The sensor as in claim 21 wherein said radiation detection structure is comprised of a separately fabricated structure that is bonded to said array of active pixels.

33. The sensor as in claim 21 and further comprising a capacitor comprised of conductor-insulator-conductor type used in parallel to said pinned diode adapted to store charges as in claim 21.

22. A MOS or CMOS based active pixel sensor comprising:

A) a substrate;

B) an array of pixels fabricated in or on said substrate, each pixel comprising a plurality of integrated circuits defining;

1) a charge collection node on which charges generated inside the photodiode are collected,

2) a charge integration node, at which charges generated in said pixel are integrated to produce pixel signals,

3) a charge sensing node from which reset signals and the pixel signals are sensed;

C) an array of pixel readout circuits fabricated in or on said substrate, each pixel readout circuits comprising a plurality of integrated circuits defining a charge sensing node from which reset signals and the pixel signals are sensed;

D) an electromagnetic radiation detection structure located above said pixel circuits for converting electromagnetic radiation into charges during charge integration cycles, said electromagnetic detection structure defining a photodiode region for each of said pixels, comprising;

1) a pixel electrode for each pixel,

2) at least one layer of charge generating material to generate charges upon the absorption of electromagnetic radiation, and

3) a surface electrode in the form of a thin transparent layer or grid located above said layers of charge generating material;

wherein said plurality of integrated circuits of each of said pixels comprises;

1) a constant gate bias transistor adapted to maintain voltage potentials of said charge collection nodes substantially constant during charge integration cycles,

2) a pinned diode having electrical capacitance adapted to store charges providing an electrical potential at said charge integration node,

3) a transfer transistor switch adapted to control the transfer of charges from the charge integration node to the charge sensing node,

wherein said plurality of integrated circuits of said plurality of pixel readout circuits comprises;

1) a diode having electrical capacitance adapted to store charges providing an electrical potential at said charge sensing node,

2) a reset transistor switch adapted to reset said charge sensing node,

3) a source follower transistor adapted to convert the charges on the charge sensing node into electrical signal, and

4) a row readout switch adapted to readout electrical signals generated in said pixels.

29. The sensor as in claim 22 wherein said radiation detection structure is comprised of a plurality of photon sensing layers deposited over said array of active pixels.

30. The sensor as in claim 22 wherein said radiation detection structure is comprised of a separately fabricated structure that is bonded to said array of active pixels.

34. The sensor as in claim 22 and further comprising a capacitor made of conductor-insulator-conductor type used in parallel to said pinned diode adapted to store charges as in claim 22.