Back-Illuminated, Thin Photodiode Arrays with Trench Isolation

• US 20090057801A1
• Filed: 08/08/2008
• Published: 03/05/2009
• Est. Priority Date: 08/10/2007
• Status: Active Grant

• Current Assignee: Array Optronix, Inc.
• Original Assignee: Semicoa
• Inventors: Papadopoulos, George, Denning, Perry A., Goushcha, Alexander O.
• Granted Patent: US 8,101,981 B2
• Time in Patent Office: Days
• US Class Current: 257/437
• CPC Class Codes: H01L 27/1443 with at least one potential jump or surface barrier
• CPC Class Codes: H01L 27/1446 in a repetitive configuration
• CPC Class Codes: H01L 27/1463 Pixel isolation structures
• CPC Class Codes: H01L 27/1464 Back illuminated imager structures
• CPC Class Codes: H01L 27/14689 MOS based technologies

Abstract

Back-illuminated, thin photodiode arrays with trench isolation. The trenches are formed on one or both sides of a substrate, and after doping the sides of the trenches, are filled to provide electrical isolation between adjacent photodiodes. Various embodiments of the photodiode arrays and methods of forming such arrays are disclosed.

Claims

1. A back-illuminated photodiode array comprising:

a substrate having first and second sides;

an array of photodiodes formed from a first side of the substrate;

trenches in the substrate forming an interconnected matrix surrounding each photodiode;

the walls of the trenches having a higher conductivity than the substrate;

the trenches being filled;

whereby the trenches provide electrical isolation between adjacent photodiodes.

2. The back-illuminated photodiode array of claim 1 wherein the trenches extend from the first side of the substrate.

3. The back-illuminated photodiode array of claim 2 further comprising a matrix of regions of the same conductivity type as the walls of the trenches and of higher conductivity than the substrate extending from the second side of the substrate, the matrix of regions of the same conductivity type as the walls of the trenches also surrounding each photodiode and aligned with the interconnected matrix surrounding each photodiode.

4. The back-illuminated photodiode array of claim 1 wherein the trenches extend from the second side of the substrate.

5. The back-illuminated photodiode array of claim 4 further comprising a matrix of regions of the same conductivity type as the walls of the trenches and of higher conductivity than the substrate extending from the first side of the substrate, the matrix of regions of the same conductivity type as the walls of the trenches also surrounding each photodiode and aligned with the interconnected matrix surrounding each photodiode.

6. The back-illuminated photodiode array of claim 1 wherein the trenches extend from the first and second sides of the substrate.

7. The back-illuminated photodiode array of claim 6 wherein the photodiodes are formed by a diffusion of the second conductivity type from the first side of the substrate.

8. The back-illuminated photodiode array of claim 7 wherein the diffusion of the second conductivity type is at the bottom of a matrix of photodiode trenches.

9. The back-illuminated photodiode array of claim 8 wherein at least one wall each photodiode trench has a region more conductive than the substrate extending from the diffusion of the second conductivity type at the bottom of a matrix of photodiode trenches to the first surface of the substrate.

10. The back-illuminated photodiode array of claim 1 wherein the walls of the trenches have the same conductivity type as the substrate.

11. The back-illuminated photodiode array of claim 1 further comprising a blanket diffusion in the second side of the substrate.

12. The back-illuminated photodiode array of claim 11 further comprising an antireflective coating on the blanket diffusion.

13. The back-illuminated photodiode array of claim 1 wherein the substrate has a thickness of approximately 300 um or less.