Photosensors Including Photodiode Control Electrodes and Methods of Operating Same

• US 20080302949A1
• Filed: 06/04/2008
• Published: 12/11/2008
• Est. Priority Date: 06/07/2007
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Ahn, Jung-chak, Kim, Yi-tae
• Granted Patent: US 7,910,872 B2
• Time in Patent Office: Days
• US Class Current: 250/206
• CPC Class Codes: H01L 31/103 the potential barrier being of the PN homojunction type
• CPC Class Codes: H04N 25/626 Reduction of noise due to residual charges remaining after image readout, e.g. to remove ghost images or afterimages
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 25/77 Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components

Abstract

A sensor includes a substrate, a floating diffusion node in the substrate, a photodiode in the substrate laterally spaced apart from the floating diffusion region and a transfer transistor coupling the photodiode and the floating diffusion region. The sensor further includes a photodiode control electrode disposed on the photodiode and configured to control a carrier distribution of the photodiode responsive to a control signal applied thereto. The floating diffusion region may have a first conductivity type, the photodiode may include a first semiconductor region of a second conductivity type disposed on a second semiconductor region of the first conductivity type, and the photodiode control electrode may be disposed on the first semiconductor region. The photodiode may be configured to receive incident light from a side of the substrate opposite the photodiode control electrode. The transfer transistor may include a gate electrode on a channel region in the substrate and the photodiode control electrode and the transfer transistor gate electrode may be separately controllable. In further embodiments, the photodiode control electrode comprises an extension of the transfer transistor gate electrode.

Claims

1. A sensor comprising:

a substrate;

a floating diffusion node in the substrate;

a photodiode in the substrate laterally spaced apart from the floating diffusion region;

a transfer transistor coupling the photodiode and the floating diffusion region; and

a photodiode control electrode disposed on the photodiode and configured to control a carrier distribution of the photodiode responsive to a control signal applied thereto.

2. The sensor of claim 1, wherein the floating diffusion region has a first conductivity type, wherein the photodiode comprises a first semiconductor region of a second conductivity type disposed on a second semiconductor region of the first conductivity type, and wherein the photodiode control electrode is disposed on the first semiconductor region.

3. The sensor of claim 1, wherein the photodiode is configured to receive incident light from a side of the substrate opposite the photodiode control electrode.

4. The sensor of claim 1, wherein the transfer transistor comprises a gate electrode on a channel region in the substrate and wherein the photodiode control electrode and the transfer transistor gate electrode are separately controllable.

5. The sensor of claim 1, wherein the transfer transistor comprises a gate electrode on a channel region in the substrate and wherein the photodiode control electrode comprises an extension of the transfer transistor gate electrode.

6. A sensor comprising:

a photodiode comprising a first semiconductor region having a first conductivity type disposed on a second semiconductor region having a second conductivity type;

a transfer transistor having a channel coupled to the second semiconductor region;

a photodiode control electrode disposed on the first semiconductor region opposite the second semiconductor region; and

a control circuit coupled to the photodiode control electrode and the transfer transistor and configured to bias the photodiode control electrode to create a majority-carrier concentration region in first semiconductor region near the photodiode control electrode.

7. The sensor of claim 6, wherein the control circuit is configured to bias the photodiode control electrode to create a majority-carrier concentration region in the first semiconductor region near the photodiode control electrode while causing the transfer transistor to impede charge transfer through the channel of the transfer transistor.

8. The sensor of claim 7, wherein the control circuit is further configured to allow charge transfer through the transfer transistor while biasing the photodiode control electrode to increase a potential across the photodiode.

9. The sensor of claim 8, wherein the control circuit is configured to bias the photodiode control electrode and a gate electrode of the transfer transistor with voltages of opposite polarities to allow charge transfer through the transfer transistor while increasing the potential across the photodiode.

10. The sensor of claim 7, wherein the control circuit is further configured to allow charge transfer through the transfer transistor while biasing the photodiode control electrode to increase a minority carrier concentration in the first semiconductor region near the photodiode control electrode.

11. The sensor of claim 10, wherein the control circuit is configured to bias the photodiode control electrode and a gate electrode of the transfer transistor to the same voltage.

12. The sensor of claim 11, wherein the photodiode control electrode comprises an extension of the transfer transistor gate electrode.

13. The sensor of claim 6, wherein the photodiode is configured to receive incident light at a surface of the second semiconductor region opposite the surface of the first semiconductor region.

14. A sensor comprising:

a photodiode comprising a first semiconductor region having a first conductivity type disposed on a second semiconductor region having a second conductivity type;

a transfer transistor having a channel coupled to the second semiconductor region;

a photodiode control electrode disposed on the first semiconductor region opposite the second semiconductor region; and

a control circuit electrically coupled to the photodiode control electrode and the transfer transistor and configured to bias the photodiode control electrode to increase a potential across the photodiode while enabling charge transfer through the transfer transistor.

15. The sensor of claim 14, wherein the control circuit is configured to bias the photodiode control electrode and a gate electrode of the transfer transistor with voltages of opposite polarities to allow charge transfer through the transfer transistor while increasing the potential across the photodiode.

16. A sensor comprising:

a photodiode comprising a first semiconductor region having a first conductivity type disposed on a second semiconductor region having a second conductivity type;

a transfer transistor having a channel coupled to the second semiconductor region;

a photodiode control electrode disposed on the first semiconductor region opposite the second semiconductor region; and

a control circuit electrically coupled to the photodiode control electrode and the transfer transistor and configured to enable charge transfer through the transfer transistor while biasing the photodiode control electrode to increase a minority carrier concentration in a portion of the first semiconductor region near the photodiode control electrode.

17. The sensor of claim 16, wherein the control circuit is configured to bias the photodiode control electrode and a gate electrode of the transfer transistor to the same voltage.

18. The sensor of claim 17, wherein the photodiode control electrode comprises an extension of the transfer transistor gate electrode.

19. A method of operating a sensor comprising a photodiode and a transfer transistor having a channel coupled to the photodiode, the method comprising

applying a bias to a photodiode control electrode disposed on the photodiode to control a carrier distribution of the photodiode while controlling the transfer transistor to impede and/or allow charge transfer from the photodiode.

20. The method of claim 19, wherein the photodiode comprises a first semiconductor region of a first conductivity type disposed on a second semiconductor region of a second conductivity type, wherein the second semiconductor region is coupled to the channel of the transfer transistor and wherein applying a bias to a photodiode control electrode disposed on the photodiode to control a carrier distribution of the photodiode while controlling the transfer transistor to impede and/or allow charge transfer from the photodiode comprises applying a bias to the photodiode control electrode to create a majority-carrier concentration in the first semiconductor region near the photodiode control electrode while impeding charge transfer from the second semiconductor region through the transfer transistor.

21. The method of claim 20, further comprising allowing charge transfer through the transfer transistor while biasing the photodiode control electrode to increase a potential across the photodiode.

22. The method of claim 19, wherein applying a bias to a photodiode control electrode disposed on the photodiode to control a carrier distribution of the photodiode while controlling the transfer transistor to impede and/or allow charge transfer from the photodiode comprises applying a bias to the photodiode control electrode to increase a potential across the photodiode while enabling charge transfer through the transfer transistor.

23. The method of claim 19, wherein the photodiode comprises a first semiconductor region of a first conductivity type disposed on a second semiconductor region of a second conductivity type, wherein the second semiconductor region is coupled to the channel of the transfer transistor and wherein applying a bias to a photodiode control electrode disposed on the photodiode to control a carrier distribution of the photodiode while controlling the transfer transistor to impede and/or allow charge transfer from the photodiode comprises applying a bias to the photodiode control electrode to increase a minority carrier concentration in the first semiconductor region near the photodiode control electrode while enabling charge transfer through the transfer transistor.