Image sensor and method for manufacturing the same

1. An image sensor, comprising:

a pixel array including a first plurality of pixels formed in a central portion of the pixel array and a second plurality of pixels formed in an edge portion of the pixel array, wherein an incident angle of light to the edge portion is greater than an incident angle of light to the central portion; and

a substantially-planar medium layer continuously disposed over the second plurality of pixels but not disposed over the first plurality of pixels.

2. The image sensor of claim 1 , further comprising a capping layer disposed over both the first plurality of pixels and the medium layer.

3. The image sensor of claim 2 , wherein the medium layer has a higher refractive index than the capping layer.

4. The image sensor of claim 3 , wherein the capping layer has a higher refractive index than air.

5. The image sensor of claim 1 , wherein the medium layer has a refractive index equal to 1.4 or higher.

6. The image sensor of claim 1 , further comprising:

a first plurality of microlenses configured to direct light toward the first plurality of pixels; and

a second plurality of microlenses configured to direct light toward the second plurality of pixels;

wherein the medium layer is disposed over the second plurality of microlenses but is not disposed over the first plurality of microlenses.

7. The image sensor of claim 1 , wherein the medium layer is configured to direct light toward the second plurality of pixels at a refractive angle that is less than the incident angle at which the light was received.

8. An image sensor, comprising:

a substrate;

a pixel array including a first plurality of pixels formed in a central portion of the substrate and a second plurality of pixels formed in an edge portion of the substrate, wherein an incident angle of light to the edge portion is greater than an incident angle of light to the central portion;

a first medium layer covering the second plurality of pixels but not covering the first plurality of pixels; and

a second medium layer covering both the first plurality of pixels and the second plurality of pixels.

9. The image sensor of claim 8 , wherein the second medium layer covering the second plurality of pixels is disposed on the first medium layer.

10. The image sensor of claim 8 , wherein the second medium layer has a lower refractive index than the first medium layer.

11. The image sensor of claim 8 , further comprising a capping layer covering the second medium layer.

12. The image sensor of claim 8 , wherein the first medium layer has a refractive index of approximately 1.5.

13. The image sensor of claim 12 , wherein the second medium layer has a refractive index in a range of approximately 1.4 to approximately 1.5.

14. The image sensor of claim 8 , further comprising:

a first plurality of microlenses configured to direct light toward the first plurality of pixels; and

a second plurality of microlenses configured to direct light toward the second plurality of pixels;

wherein the first medium layer is configured to cover the second plurality of microlenses but not the first plurality of microlenses; and

wherein the second medium layer is configured to cover both the first plurality of microlenses and the second plurality of microlenses.

15. The image sensor of claim 8 , wherein the first medium layer and second medium layer are configured to cause a greater change between incident angle and refractive angle for light directed toward the second plurality of pixels than light directed toward the first plurality of pixels.

16. An image sensor, comprising:

a substrate including a plurality of photodiodes, wherein the plurality of photodiodes comprises a first plurality of photodiodes in a central portion of the substrate and a second plurality of photodiodes in an edge portion of the substrate;

an over-coating layer formed over the plurality of photodiodes;

a light-refracting layer including a plurality of layers sequentially disposed in a decreasing order of refractive indices, wherein:

the plurality of layers are configured to direct light received by the light-refracting layer toward the plurality of photodiodes at a refractive angle that is less than an incident angle at which the light-refracting layer received the light;

a first layer of the plurality of layers is formed over the second plurality of photodiodes but not over the first plurality of photodiodes; and

a second layer of the plurality of layers is formed over both the first layer and the first plurality of photodiodes.

17. The image sensor of claim 16 , further comprising a capping layer formed over the light-refracting layer, wherein the capping layer has a refractive index less than the respective refractive indices of the plurality of layers.

18. The image sensor of claim 17 , wherein:

the first layer of the plurality of layers has a refractive index higher than 1.5; and

the second layer of the plurality of layers has a refractive index in a range of approximately 1.4 to approximately 1.45.

19. The image sensor of claim 16 , further comprising a plurality of microlenses formed over the over-coating layer and configured to further direct light toward the plurality of photodiodes.

20. The image sensor of claim 16 , further comprising:

a first plurality of microlenses formed over the over-coating layer and configured to further direct light toward the first plurality of photodiodes; and

a second plurality of microlenses formed over the over-coating layer and configured to further direct light toward the second plurality of photodiodes;

wherein the first layer of the plurality of layers is formed over the second plurality of microlenses but not over the first plurality of microlenses; and

wherein the second layer of the plurality of layers is formed over both the first layer and the first plurality of microlenses.