METHOD OF FABRICATING BACKSIDE ILLUMINATED IMAGE SENSOR

• US 20100087029A1
• Filed: 12/09/2009
• Published: 04/08/2010
• Est. Priority Date: 03/06/2006
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Shiau, Gwo-Yuh, Fu, Shih-Chi, Hsieh, Yuan-Chih, Shiu, Feng-Jia, Yao, Liang-Lung
• Granted Patent: US 7,923,344 B2
• Time in Patent Office: Days
• US Class Current: 438/70
• 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 27/14621 Colour filter arrangements
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14689 MOS based technologies
• CPC Class Codes: Y10S 438/977 Thinning or removal of substrate

Abstract

A method for fabricating a backside illuminated image sensor is provided. An exemplary method can include providing a substrate with a front surface and a back surface; forming a first alignment mark for global alignment on the front surface of the substrate; forming a second alignment mark for fine alignment in a clear-out region on the front surface of the substrate; aligning the substrate from the back surface using the first alignment mark; and removing a portion of the back surface of the substrate at the clear-out region for locating the second alignment mark.

Claims

1. A method for fabricating an electronic device, comprising:

providing a substrate with a front surface and a back surface;

forming a first alignment mark for global alignment on the front surface of the substrate;

forming a second alignment mark for fine alignment in a clear-out region on the front surface of the substrate;

aligning the substrate from the back surface using the first alignment mark; and

removing a portion of the back surface of the substrate at the clear-out region for locating the second alignment mark.

2. The method of claim 1, further including adding a supporting layer to the front surface of the substrate.

3. The method of claim 1, further including reducing a thickness of the substrate prior to aligning the substrate.

4. The method of claim 1 wherein forming the first alignment mark includes forming the first alignment mark by a 1×

reticle pattern.

5. The method of claim 1 wherein forming the second alignment mark includes forming a minor-image type alignment mark or an overlay mark.

6. The method of claim 1 wherein forming the second alignment mark includes forming the second alignment mark by a 4×

reticle pattern.

7. The method of claim 1 wherein removing the portion of the back surface is performed after aligning the substrate.

8. The method of claim 7 wherein removing the portion of the back surface includes performing a selective etching process.

9. The method of claim 1 wherein aligning the substrate from the back surface using the first alignment mark includes aligning the first alignment mark with an alignment mark of a reticle.

10. The method of claim 1, further including aligning the substrate from the back surface using the second alignment mark.

11. The method of claim 10, further including:

forming a doped region within an active region of the substrate; and

forming a color filter and a mircolens on the back surface of the substrate and aligned with the doped region.

12. A method for fabricating a back-side illuminated image sensor, comprising:

providing a semiconductor substrate having a front surface, back surface, active region, and clear-out region;

forming a first alignment mark on the front surface of the substrate;

forming a second alignment mark on the front surface of the clear-out region;

selectively etching a portion of the substrate from the back surface within the clear-out region by performing registration from the back surface and using the first alignment mark as a reference; and

processing the active region of the substrate from the back surface by performing registration from the back surface and using the second alignment mark as a reference.

13. The method of claim 12 wherein performing registration from the back surface of the substrate includes using radiation and optically detecting and aligning one of the first and second alignment marks with an alignment mark on a reticle pattern.

14. The method of claim 13 wherein the alignment mark on the reticle pattern is a minor-image of the one of the first and second alignment marks.

15. The method of claim 12 wherein the alignment mark on the reticle pattern is a minor-image shape that overlays the one of the first and second alignment marks.

16. The method of claim 12 wherein forming the first alignment mark includes forming the first alignment mark by a 1×

reticle pattern.

17. The method of claim 12 wherein forming the second alignment mark includes forming the second alignment mark by a 4×

reticle pattern.

18. The method of claim 12 further including forming a supporting layer over the front surface of the substrate.

19. The method of claim 12 further including thinning the semiconductor substrate from the back surface prior to selectively etching the portion of the substrate from the back surface within the clear-out region.

20. The method of claim 12 wherein processing the active region of the substrate from the back surface includes:

forming first, second, and third doped regions within the active region of the substrate;

forming first, second, and third color filters on the back surface of the substrate and aligned with the first, second, and third doped regions, respectively; and

forming a microlens over the first, second, and third color filters.