Pinned floating photoreceptor with active pixel sensor

A pinned photodiode is operated without a transfer gate. This is done by forming a pinned photodiode which has a selective connection to the substrate. When the connection is turned on, the photodiode is pinned to the substrate, and kept at a specified potential. When the connection is off, the photodiode is disconnected from the substrate and hence floats. In this way, the area above the photoreceptor can be used both for a reception area and for a charge transfer area.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will now be described with reference to the attached drawings, in which:

FIG. 1 shows a connection to a convention pinned photodiode;

FIG. 2 shows a layout of the element;

FIG. 3 shows a simplified diagram of the diode;

FIGS. 4A-4D show a more detailed diagram of the pinned photodiode and its connection;

FIGS. 5A and 5B show equivalent schematics; and

FIG. 6 shows an array of sensors in accordance with the teachings of the invention.

1. An image sensor, comprising:

2. A sensor as in claim 1 wherein each of said photoreceptors includes a virtual floating gate which transfers charge from the photoreceptor to receptor area.

3. A sensor as in claim 1 wherein said surface region buries a charge sensitive area.

4. A sensor as in claim 3 further comprising a switching element which switches said surface region between the pinned condition and the floating condition.

5. A sensor as in claim 4 wherein said surface region is in said floating condition during readout but in said pinned condition during integration.

6. A sensor as in claim 4 wherein said surface region, when pinned, is connected to a substrate of the device.

7. A sensor as in claim 1 wherein said surface region overlies a charge sensitive area; and

8. A method of operating a image sensor, comprising:

9. A selectively pinned image sensor, comprising:

10. A sensor as in claim 9 further comprising a controller which produces a command indicating whether said overlying substrate portion should be pinned or not.

11. A sensor as in claim 9, wherein said barrier is a depletion layer.

12. A selectively pinned image sensor, comprising:

13. A sensor as in claim 12 wherein one of said contact portions is connected to a drain structure enabling connection to a drain voltage for reset.

14. A sensor as in claim 13 wherein said switching element is a transistor making said connection.

15. A sensor as in claim 13 further comprising a plurality of gates coupled to said plurality of peninsulas.

16. A sensor as in claim 15 wherein one of said gates connects via a first transistor to an output and another of said gates connects via a second transistor to a bias level.

17. A sensor as in claim 16 wherein one of said first and second transistors in NMOS and another of said first and second transistors is PMOS.

18. A sensor as in claim 12 wherein said photoreceptor is a photodiode.

19. A sensor as in claim 18 wherein said barrier is a depletion layer.

20. A method of operating a photoreceptor, comprising: