Anti-reflective coating with high refractive index material at air interface

• US 10,644,048 B2
• Filed: 02/01/2017
• Issued: 05/05/2020
• Est. Priority Date: 02/01/2017
• Status: Active Grant

• Current Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Original Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Inventors: Fan, Chun-Sheng, Tsai, Chen-Wei, Lin, Wei-Feng
• Primary Examiner(s): Inoussa, Mouloucoulaye
• Application Number:
  US15/421,879
• Publication Number:
  US 20180219034A1
• Time in Patent Office: 1,189 Days
• Field of Search: 415200, 428448, 428446, 428451, 428615, 428627, 428641, 428655, 428663, 428664, 359245, 438 24
• CPC Class Codes: H01L 27/1462 Coatings
• CPC Class Codes: H01L 27/14627 Microlenses

Abstract

An optical element comprising a transparent substrate and an anti-reflective coating, wherein the anti-reflective coating further comprises at least a transparent, high refractive index layer and a transparent, low refractive index layer, wherein the high refractive index layer is in contact with the low refractive index layer; and wherein the high refractive index layer is situated at an interface between the anti-reflective coating and air. Further, the low refractive index layer may be silicon oxide; the high refractive index layer may be tantalum oxide or silicon nitride.

Claims

1. An optical element comprising a transparent substrate and an anti-reflective coating, wherein the anti-reflective coating further comprises:

at least a transparent, high refractive index layer and a transparent, low refractive index layer, wherein the high refractive index layer is in contact with the low refractive index layer; and

wherein the high refractive index layer is situated at an interface between the antireflective coating and air;

wherein the high refractive index layer has a thickness that has a range that is substantially equal to 1-2 nm;

wherein light reflected at an interface between air and the high refractive index layer, light reflected at an interface between the high refractive index layer and the low refractive layer, and light reflected at an interface between the low refractive index layer and the transparent substrate have destructive interference; and

wherein the anti-reflective coating is based on destructive interference.

2. The optical element of claim 1, wherein the low refractive index layer is a silicon dioxide layer.

3. The optical element of claim 2, wherein the high refractive index layer is a tantalum oxide layer.

4. The optical element of claim 2, wherein the high refractive index layer is a silicon nitride layer.

5. The optical element of claim 2, wherein the anti-reflective coating comprises seventeen, additional alternating layers of transparent high refractive index and low-refractive index materials.

6. The optical element of claim 5, wherein the substrate is in contact with a first layer of low refractive index material.

7. The optical element of claim 1, wherein the substrate is a flat cover glass.

19. The optical element of claim 5, wherein the additional seventeen layers, the high refractive index layer, and the low refractive layer form nineteen layers having thicknesses:

8. An image sensor package comprising a CMOS image sensor and an optical element, wherein the optical element further comprises a transparent substrate and an antireflective coating, wherein the anti-reflective coating further comprises:

at least a transparent, high refractive index layer and a transparent, low refractive index layer, wherein the high refractive index layer is in contact with the low refractive index layer; and

wherein the high refractive index layer is situated at an interface between the antireflective coating and air;

wherein light reflected at an interface between air and the high refractive index layer, light reflected at an interface between the high refractive index layer and the low refractive layer, and light reflected at an interface between the low refractive index layer and the transparent substrate have destructive interference; and

wherein the anti-reflective coating is based on destructive interference.

9. The image sensor package of claim 8, wherein the low refractive index layer is a silicon dioxide layer.

10. The image sensor package of claim 9, wherein the high refractive index layer is a tantalum oxide layer.

11. The image sensor package of claim 9, wherein the high refractive index layer is a silicon nitride layer.

12. The image sensor package of claim 9, wherein the anti-reflective coating comprises seventeen, additional alternating layers of transparent high-refractive index and low-refractive index materials.

13. The image sensor package of claim 12, wherein the substrate is in contact with a first layer of low refractive index material.

14. The image sensor package of claim 13, wherein the high refractive index layer has a thickness that has a range that is substantially equal to 1-2 nm.

15. The image sensor package of claim 8, wherein the substrate is a flat cover glass.

16. An optical element comprising:

a transparent substrate;

a first layer of transparent, low refractive index material that is in contact with the substrate;

a second layer of transparent, high refractive index material that is in contact with the first layer;

additional, alternating layers of transparent low-refractive index and high-refractive index materials;

a nineteenth layer of transparent, high-refractive index material that is situated at an interface between the nineteenth layer and air;

wherein the nineteenth layer has a thickness that has a range that is substantially equal to 1-2 nm;

wherein light reflected at an interface between air and the high refractive index layer, light reflected at an interface between the high refractive index layer and the low refractive layer, and light reflected at an interface between the low refractive index layer and the transparent substrate have destructive interference; and

wherein a combination of the layers of transparent low-refractive index and high refractive index materials rendering an anti-reflective coating based on destructive interference.

17. The optical element of claim 16, wherein the nineteenth layer is a tantalum oxide layer, layer.

18. The optical element of claim 16, wherein the nineteenth layer is a silicon nitride.