Dual pinned diode pixel with shutter

• US 20060044243A1
• Filed: 08/30/2004
• Published: 03/02/2006
• Est. Priority Date: 08/30/2004
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Rysinski, Jeffrey
• Granted Patent: US 8,072,520 B2
• Time in Patent Office: Days
• US Class Current: 345/92
• CPC Class Codes: H04N 25/53 Control of the integration time
• CPC Class Codes: H04N 25/771 comprising storage means other than floating diffusion

Abstract

A pixel having an electronic shutter suitable for use in a pixel array of an imaging device includes a pinned diode and a shutter transistor. The pinned diode is utilized as a storage device while the shutter transistor controls charge transfer from the electronic shutter. The use of a pinned diode as a charge storage device for the electronic shutter permits greater charge transfer efficiency, has lower leakage (or “dark” current), and permits the resulting pixel to have a greater fill factor than pixels utilizing conventional electronic shutter circuits.

Claims

1. A pixel, comprising:

a light sensitive element for generating a photo generated charge;

an electronic shutter circuit, for transferring and storing the charge from said light sensitive element, said electronic shutter comprising;

a pinned diode charge storage element; and

a shutter control element, said shutter control element having a shutter control input coupled to said light sensitive element and an output coupled to said pinned diode; and

a transfer control element, for transferring charge from said charge storage element to a pixel output circuit.

2. The pixel of claim 1, wherein said charge storage element is a pinned photodiode.

3. The pixel of claim 2, further comprising:

a light shielding element arranged to shield said pinned photodiode from light incident upon said light sensitive element.

4. The pixel of claim 1, wherein said light sensitive element is a photodiode.

5. The pixel of claim 4, wherein said photodiode is a pinned photodiode.

6. The pixel of claim 1, wherein said transfer control element is a transistor having one source/drain coupled to said electronic shutter circuit.

7. The pixel of claim 1, wherein said shutter control element is a transistor having one source/drain coupled to said charge storage element and another source/drain coupled to said light sensitive element.

8. An imager, comprising:

a pixel array, said pixel array comprising a plurality of pixels organized into a plurality of rows and a plurality of columns, each of said pixels comprising;

a light sensitive element for generating a photo generated charge;

an electronic shutter circuit, for transferring and storing the charge from said light sensitive element, said electronic shutter comprising;

a pinned diode charge storage element; and

a shutter control element, said shutter control element having a shutter control input coupled to said light sensitive element and an output coupled to said pinned diode; and

a transfer control element, for transferring charge from said charge storage element to a pixel output circuit.

a image processing circuit, for receiving a signal said plurality of pixels, and for further processing said signal;

a switching circuit, coupled to said pixel array, for controllably coupling different ones of said plurality of pixels in said pixel array to said image processing circuitry; and

a control circuit, for operating said switching circuit to transfer signals from each of said pixels to said image processing circuit, and for controlling said electronic shutter circuit of each of said plurality of pixels.

9. The imager of claim 8, wherein said charge storage element is a pinned photodiode.

10. The imager of claim 9, further comprising:

a light shielding element arranged to shield said pinned photodiode from light incident upon said light sensitive element.

11. The imager of claim 8, wherein said light sensitive element is a photodiode.

12. The imager of claim 11, wherein said photodiode is a pinned photodiode.

13. The imager of claim 8, wherein said transfer control element is a transistor having one source/drain coupled to said electronic shutter circuit.

14. The imager of claim 8, wherein said shutter control element is a transistor having one source/drain coupled to said charge storage element and another source/drain coupled to said light sensitive element.

15. A method of operating an imager having a plurality of pixels, each pixel including an electronic shutter, the method comprising:

in each pixel of said imager,

selectively electrically coupling a pinned diode charge storage element to a stream of photo generated charges produced by a light sensitive element exposed to incident light;

storing said stream of photo generated charges in said charge storage element when said charge storage element is electrically coupled to said light sensitive element; and

selectively electrically coupling said charge storage element to an output circuit of a pixel.

16. The method of claim 15, wherein said charge storage element is coupled to said output circuit when said charge storage element is not electrically coupled to said light sensitive element.

17. The method of claim 16, wherein said pinned diode charge storage element is a pinned photodiode and said method further comprises shielding said pinned photodiode from said incident light.

18. A system, comprising:

processing element; and

an imager, coupled to said processing element, said imager comprising;

a pixel array, said pixel array comprising a plurality of pixels organized into a plurality of rows and a plurality of columns, each of said pixels comprising;

a light sensitive element for generating a photo generated charge;

an electronic shutter circuit, for transferring and storing the charge from said light sensitive element, said electronic shutter comprising;

a pinned diode charge storage element; and

a shutter control element, said shutter control element having a shutter control input coupled to said light sensitive element and an output coupled to said pinned diode; and

a transfer control element, for transferring charge from said charge storage element to a pixel output circuit;

a image processing circuit, for receiving a signal said plurality of pixels, and for further processing said signal;

a switching circuit, coupled to said pixel array, for controllably coupling different ones of said plurality of pixels in said pixel array to said image processing circuitry; and

a control circuit, for operating said switching circuit to transfer signals from each of said pixels to said image processing circuit, and for controlling said electronic shutter circuit of each of said plurality of pixels.

19. The system of claim 18, wherein said charge storage element is a pinned photodiode.

20. The system of claim 19, further comprising:

a light shielding element arranged to shield said pinned photodiode from light incident upon said light sensitive element.

21. The system of claim 18, wherein said light sensitive element is a photodiode.

22. The system of claim 21, wherein said photodiode is a pinned photodiode.

23. The system of claim 18, wherein said transfer control element is a transistor having one source/drain coupled to said electronic shutter circuit.

24. The system of claim 18, wherein said shutter control element is a transistor having one source/drain coupled to said charge storage element and another source/drain coupled to said light sensitive element.

25. An imager, comprising:

a pixel array comprising a plurality of pixels arranged into a plurality of rows, each of said pixels including a light sensitive element respectively coupled in series with an in-pixel shutter circuit, a transfer transistor, and an output circuit; and

a control circuit for controlling said plurality of pixels;

wherein

said control circuit simultaneously and uniformly controls a conductivity of the in-pixel shutter circuit in each of said pixels, and

said control circuit controls a conductivity of said transfer transistor of said pixels on a row-by-row basis.

26. The imager of claim 25, wherein in each pixel, said shutter circuit comprises:

a shutter transistor; and

a charge storage node;

wherein said shutter control transistor include one source/drain coupled to said light sensitive element, and another source/drain coupled to said charge storage node.

27. The imager of claim 26, wherein said charge storage node is a pinned diode.

28. The imager of claim 27, wherein said pinned diode is a pinned photodiode.

29. The imager of claim 28, wherein said pinned photodiode is shielded from any incident light.

30. A method for fabricating an imaging device, comprising:

providing a pixel array comprising a plurality of pixels arranged into a plurality of rows, each of said pixels including a light sensitive element respectively coupled in series with an in-pixel shutter circuit, a transfer transistor, and an output circuit; and

providing a control circuit for controlling said plurality of pixels;

wherein

said control circuit simultaneously and uniformly controls a conductivity of the in-pixel shutter circuit in each of said pixels, and

said control circuit controls a conductivity of said transfer transistor of said pixels on a row-by-row basis.