Method of fabricating an imaging device for collecting photons

• US 7,358,103 B2
• Filed: 02/21/2006
• Issued: 04/15/2008
• Est. Priority Date: 06/10/2004
• Status: Expired

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Li, Jiutao, Li, Jin
• Primary Examiner(s): COLEMAN, WILLIAM D
• Application Number:
  US11/357,343
• Publication Number:
  US 20060138495A1
• Time in Patent Office: 784 Days
• Field of Search: 438/23, 438/24, 438/29, 359/627, 359/636
• US Class Current: 438/29
• CPC Class Codes: H01L 27/14601 Structural or functional details thereof
• CPC Class Codes: H01L 27/1462 Coatings
• CPC Class Codes: H01L 27/14623 Optical shielding
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements

Abstract

A photon collector has a reflecting metal layer to increase photon collection efficiency in a solid state imaging sensor. The reflecting metal layer reflects incident light internally to a photosensor. A plurality of photon collectors is formed in a wafer substrate over an array of photosensors. The photon collector is formed in an opening in an insulating layer provided over each photosensor.

Claims

1. A method of fabricating an imaging device, said method comprising:

forming a plurality of photosensors on a wafer;

forming an insulating layer on the wafer over the plurality of photosensors;

forming a respective opening in the insulating layer, above the plurality of photosensors; and

depositing a reflecting material on sidewalls of each opening.

2. A method according to claim 1, wherein said the reflecting material is a metal.

3. A method according to claim 1, wherein the diameter of an upper portion of each opening is greater than the diameter at the base of each opening.

4. A method according to claim 1, wherein the sidewalls of each opening are selected from the group consisting of substantially perpendicular, substantially diagonal, curved surfaces, and combinations thereof.

5. A method according to claim 1, further comprising depositing the reflecting material through a collimated structure.

6. A method according to claim 1, further comprising providing an optically transparent material contained within the sidewalls of each opening.

7. A method according to claim 6, wherein the optically transparent material is selected from the group consisting of spun-on glass and photoresist.

8. A method according to claim 2, wherein the reflecting material is aluminum.

9. A method according to claim 2, wherein the reflecting material is silver.

10. A method according to claim 9, the method further including forming a barrier layer between the silver and the insulating layer.

11. A method according to claim 5, wherein the wafer is held at an angle relative to the collimated structure.

12. The method of claim 5, wherein the wafer is rotated relative to the collimated structure during deposition of the reflecting material.

13. A method according to claim 11, wherein the angle is selected such that the reflecting material is not deposited over the photosensors.

14. A method of fabricating an imaging device, said method comprising:

forming a photodiode within a semiconductor substrate located beneath an insulating layer;

providing an etch stop layer over said the photodiode;

etching an opening in the insulating layer above the photodiode to the etch stop layer;

depositing a light-reflecting metal on sidewalls of the opening; and

filling the opening with an optically transparent material.

15. The method of claim 14, wherein the light-reflecting metal is deposited on the sidewalls of the opening using a collimated source of the light-reflecting metal.