Image sensor having curved micro-mirrors over the sensing photodiode and method for fabricating

• US 8,338,900 B2
• Filed: 01/06/2011
• Issued: 12/25/2012
• Est. Priority Date: 10/26/2006
• Status: Active Grant

• Current Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Original Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Inventors: Venezia, Vincent, Tai, Hsin-Chih
• Primary Examiner(s): Chen, Jack
• Application Number:
  US12/985,950
• Publication Number:
  US 20110140221A1
• Time in Patent Office: 719 Days
• Field of Search: 257290-294, 257/21, 257/432, 257/E31.127
• US Class Current: 257/432
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H01L 27/14629 Reflectors
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements

Abstract

The invention involves the integration of curved micro-mirrors over a photodiode active area (collection area) in a CMOS image sensor (CIS) process. The curved micro-mirrors reflect light that has passed through the collection area back into the photo diode. The curved micro-mirrors are best implemented in a backside illuminated device (BSI).

Claims

1. An image sensor comprising:

a light sensitive element configured to receive light from a light-incident side of the image sensor;

a pre-metal dielectric layer;

a micro-mirror coupled to the pre-metal dielectric layer such that the light sensitive element is between the light incident side of the image sensor and the micro-mirror, wherein the micro-mirror includes;

a micro-lens coupled to the pre-metal dielectric layer; and

a metal layer coupled to the micro-lens; and

a layer of dielectric material covering the micro-mirror.

2. The image sensor as in claim 1, wherein the micro-mirror is curved and disposed above the pre-metal dielectric layer.

3. The image sensor of claim 1, wherein the micro-mirror is disposed to redirect incident light back through to the light sensitive element.

4. The image sensor of claim 1, wherein the light sensitive element includes a photodiode.

5. The image sensor of claim 1, wherein the micro-lens is a first micro-lens and wherein the image sensor further includes a second micro-lens disposed on the light-incident side of the image sensor, such that the light sensitive element is disposed between the first micro-lens and the second micro-lens.

6. A backside illuminated image sensor comprising:

a light sensitive element configured to receive light from a backside of the image sensor;

a pre-metal dielectric layer;

a micro-mirror coupled to the pre-metal dielectric layer such that the light sensitive element is between the backside of the image sensor and the micro-mirror, wherein the micro-mirror includes;

a micro-lens coupled to the pre-metal dielectric layer; and

a metal layer coupled to the micro-lens; and

a layer of dielectric material covering the micro-mirror.

7. The image sensor as in claim 6, wherein the micro-mirror is curved and disposed above the pre-metal dielectric layer.

8. The image sensor of claim 6, wherein the micro-mirror is disposed to redirect incident light back through to the light sensitive element.

9. The image sensor of claim 6, wherein the light sensitive element includes a photodiode.

10. The image sensor of claim 6, wherein the micro-lens is a first micro-lens and wherein the image sensor further includes a second micro-lens disposed on the backside of the image sensor, such that the light sensitive element is disposed between the first micro-lens and the second micro-lens.