CMOS image sensor having pinned diode floating diffusion region

• US 7,119,322 B2
• Filed: 12/13/2005
• Issued: 10/10/2006
• Est. Priority Date: 09/05/2003
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Micron Technology, Inc.
• Inventors: Hong, Sungkwon C.
• Primary Examiner(s): Luu, Thanh X.
• Application Number:
  US11/299,665
• Publication Number:
  US 20060131481A1
• Time in Patent Office: 301 Days
• Field of Search: 250/208.1, 250/214.1, 257/292, 348/308
• US Class Current: 250/214.1
• CPC Class Codes: H01L 27/14609 Pixel-elements with integrated switching, control, storage or amplification elements scanning details of imagers (circuitry of solid-state image sensors H04N25/00); circuitry of imagers H04N25/70
• CPC Class Codes: H01L 27/1463 Pixel isolation structures
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 27/14689 MOS based technologies
• CPC Class Codes: H04N 25/575 with a response composed of multiple slopes
• CPC Class Codes: H04N 25/59 by controlling the amount of charge storable in the pixel, e.g. modification of the charge conversion ratio of the floating node capacitance

Abstract

The present invention provides an image sensor having a pinned floating diffusion region in addition to a pinned photodiode. The pinned floating diffusion region increases the capacity of the sensor to store charge, increases the dynamic range of the sensor and widens intra-scene intensity variation.

Claims

1. A method of forming a pixel sensor cell comprising:

forming said pixel sensor cell having a photoconversion device having a first pinning potential (V_PIN1) and a charge collection region having a second pinning potential (V_PIN2), wherein V_PIN2 is different from V_PIN1 said charge collection region having a first doped region of a first conductivity type;

forming a second doped region associated with said charge collection region having a second conductivity type;

forming a contact connected to said charge collection region; and

forming a third doped region having said first conductivity type under said contact and associated with said charge collection region.

2. The method according to claim 1, wherein V_PIN2 is greater than V_PIN1.

3. The method according to claim 1, wherein said third doped region is doped with a higher dopant concentration of said first conductivity type than said first doped region of said charge collection region.

4. The method according to claim 1, wherein said charge collection region is a floating diffusion region.

5. The method according to claim 1, wherein said photoconversion device is a photodiode.

6. The method according to claim 1, wherein said second doped region is doped p+.

7. The method according to claim 1, wherein said second doped region and said third doped region are separated from one another by a portion of said first doped region.

8. A method of forming a pixel sensor cell comprising:

forming said pixel sensor cell having a photoconversion device and a charge collection region. said charge collection region having a first doped region of a first conductivity type;

forming a second doped region associated with said charge collection region having a second conductivity type;

forming a contact connected to said charge collection region;

implanting a third doped region having said first conductivity type under said contact and associated with said charge collection region; and

forming a storage capacitor connected to said third doped region.

9. The method according to claim 8, further comprising connecting said storage capacitor to said third doped region via a contact.

10. The method according to claim 9, wherein said contact is a low ohmic contact.

11. A method of forming a pixel sensor cell comprising:

forming said pixel sensor cell having a photoconversion device and a charge collection region, said charge collection region having a first doped region of a first conductivity type;

forming a second doped region associated with said charge collection region having a second conductivity type;

forming a contact connected to said charge collection region; and

implanting a third doped region having said first conductivity type under said contact and associated with said charge collection region,

wherein said second doped region surrounds said third doped region, said third doped region extending into said first doped region.

12. The method according to claim 11, wherein said photoconversion device has a first pinning potential (V_PIN1) and said charge collection region has a second pinning potential (V_PIN2), wherein V_PIN2 is different from V_PIN1.

13. The method according to claim 12, wherein V_PIN2 is greater than V_PIN1.

14. The method according to claim 11, wherein said third doped region is doped with a higher dopant concentration of said first conductivity type than said first doped region of said charge collection region.

15. The method according to claim 11, wherein said charge collection region is a floating diffusion region.

16. The method according to claim 11, wherein said photoconversion device is a photodiode.

17. The method according to claim 11, further forming a storage capacitor and connecting said storage capacitor to said third doped region.

18. The method according to claim 17, further comprising forming a low ohmic contact to connect said storage capacitor to said third doped region.