Method of forming barrier regions for image sensors

• US 8,105,864 B2
• Filed: 11/17/2006
• Issued: 01/31/2012
• Est. Priority Date: 02/02/2004
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Inventors: Rhodes, Howard E., Mauritzson, Richard A., Quinlin, William T.
• Primary Examiner(s): Kraig, William F
• Application Number:
  US11/600,891
• Publication Number:
  US 20070063301A1
• Time in Patent Office: 1,901 Days
• Field of Search: 257230-232, 257443-446, 257/E27.139, 257/E27.145, 257/E27.162, 438/75, 438/78, 438/79
• US Class Current: 438/79
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14607 Geometry of the photosensitive area
• 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 27/14645 Colour imagers
• CPC Class Codes: H01L 27/14654 Blooming suppression
• CPC Class Codes: H01L 27/14689 MOS based technologies

Abstract

Embodiments of the invention provide an image sensor that includes a barrier region for isolating devices. The image sensor comprises a substrate and an array of pixel cells formed on the substrate. Each pixel cell comprises a photo-conversion device. The array comprises a first pixel cell having a first configuration, a second pixel cell having a second configuration, and at least one barrier region formed between the first and second pixel cells for capturing and removing charge. The barrier region comprises a charge accumulation region of a particular conductivity type in a substrate electrically connected to a voltage source terminal. The charge accumulation region accumulates charge and prevents charge transference from a pixel cell or peripheral circuitry on one side of the barrier region to a pixel cell on another side of the barrier region.

Claims

1. A method of forming an image sensor, the method comprising:

providing a substrate;

providing an array of pixel cells on the substrate, the array comprising an active region of pixels having a first configuration for sensing an image and providing signals representing a sensed image and a black region of pixels having a second configuration which does not provide signals representing the sensed image; and

forming at least one barrier region by forming a charge accumulation region of a particular conductivity type on the substrate and non-switchably electrically connecting the charge accumulation region to a voltage source terminal, the barrier region completely surrounding at least the pixels in the active region and separating the pixels in the active and black regions.

2. The method of claim 1, wherein the act of forming the charge accumulation region comprises forming either an np or pnp diode.

3. The method of claim 1, wherein the act of forming the charge accumulation region comprises forming the charge accumulation region with n-type conductivity, and wherein the act of electrically connecting the charge accumulation region comprises electrically connecting the charge accumulation region to a positive voltage source terminal.

4. The method of claim 3, wherein the act of forming the charge accumulation region comprises forming the charge accumulation region using an n-type implant dose within the range of approximately 5×

10¹² to approximately 1×

10¹⁴ atoms/cm².

5. The method of claim 3, wherein the act of forming the charge accumulation region comprises forming the charge accumulation region using an n-type implant dose within the range of approximately 2×

10¹² atoms/cm² to approximately 1×

10¹⁴ atoms/cm².

6. The method of claim 3, wherein the act of forming the charge accumulation region comprises forming the charge accumulation region using an n-type implant dose greater than approximately 1×

10¹⁴ atoms/cm².

7. The method of claim 1, wherein the act of forming the charge accumulation region comprises forming the charge accumulation region with p-type conductivity, and wherein the act of electrically connecting the charge accumulation region comprises non-switchably electrically connecting the charge accumulation region to a ground voltage source terminal.

8. The method of claim 1, wherein the act of non-switchably connecting the charge accumulation region to a voltage source terminal comprises forming a contact and a metal connection and the act of forming the barrier region comprises forming the contact region of the particular conductivity type below the contact.

9. The method of claim 8, wherein the act of forming the contact region comprises forming the contact region using an n-type implant dose greater than approximately 1×

10¹⁴ atoms/cm².

10. The method of claim 1, further comprising forming at least one wiring layer for routing electrical signals over the barrier region.

11. The method of claim 1, further comprising forming a plurality of wiring layers for routing electrical signals over the barrier region, the plurality of wiring layers not formed parallel to each other.

12. The method of claim 1, further comprising forming at least one wiring layer for routing electrical signals over the first and second pixel cells such that the at least one wiring layer does not block light from reaching the respective photo-conversion devices.

13. The method of claim 12, wherein the act of forming the at least one wiring layer comprises forming the at least one wiring layer over the first pixel cell, the at least one barrier region, and the second pixel cell.

14. The method of claim 1, wherein the act of forming the at least one barrier region comprises forming the at least one barrier region as at least a portion of a pixel cell in the array.

15. The method of claim 1, wherein the act of forming the at least one barrier region comprises forming the at least one barrier region as a group of pixel cells in the array and forming a charge accumulation region that is continuous within the substrate between the pixel cells of the group.

16. The method of claim 15, wherein the act of forming the at least one barrier region comprises forming the at least one barrier region as either a row or column of pixel cells.

17. The method of claim 1, wherein the act of forming the at least one barrier region further comprises forming at least one transistor.

18. The method of claim 1, wherein the barrier region separates the active region and black region from peripheral circuitry of the image sensor.

19. The method of claim 1, wherein the array of pixel cells comprises a plurality of black regions and the barrier region separates each from the active region.

20. A method of forming an image sensor, the method comprising:

providing a substrate;

forming an array of pixel cells on the substrate, the array comprising an active region of pixels having a first configuration for sensing an image and providing a signal representing a sensed image and a black region of pixels having a second configuration and which does not provide signals representing the sensed image; and

forming at least one barrier region of pixels on the substrate of the image sensor having a third configuration that is different than the first configuration and second configuration, the at least one barrier region completely surrounding at least the pixels in the active region and black regions and separating the pixels in the active and black regions such that charge transference between them is prevented, and comprising a charge accumulation region electrically connected to a voltage source at a terminal arranged at a location that is different than a location at which the first pixel cells and the second pixel cells are connected to the voltage source.

21. A method of forming an image processor, the method comprising:

providing a processor; and

coupling an image sensor to the processor, the image sensor comprising;

a substrate,

an array of pixel cells arranged on the substrate, the array comprising a first pixel cell having a first configuration and a black region of pixels having a second configuration, and

at least one barrier region arranged on the substrate completely surrounding at least the pixels in the active and black regions and separating the pixels in the active and black regions such that charge transference between them is prevented, the barrier region comprising a contiguous charge accumulation region on the substrate and non-switchably electrically connected to a voltage source terminal.