Image sensor having grid patterns embedded in anti-reflective layer

1. An image sensor comprising:

photoelectric conversion elements formed in a substrate, each photoelectric conversion element responsive to light to produce a photo sensing electrical signal;

isolation regions disposed between adjacent photoelectric conversion elements and configured to isolate the photoelectric conversion elements from one another;

an anti-reflective layer formed over the substrate to reduce an optical reflection to facilitate optical transmission of light incident to the photoelectric conversion elements through the anti-reflective layer;

grid patterns formed over the isolation regions to provide an optical separation between two adjacent photoelectric conversion elements;

color filters arranged between the grid patterns, each color filter structured to select a designated color in the incident light to transmit through a corresponding photoelectric conversion element; and

microlenses respectively formed over the color filters to direct incident light to the photoelectric conversion elements through the color filters,

wherein each of the grid patterns comprises an upper grid portion and a lower grid portion disposed below the upper grid portion, and

a bottom of the lower grid portion is embedded in the anti-reflective layer,

wherein the upper grid portion has a larger horizontal width than that of a portion of the lower grid portion, the portion of the lower grid portion disposed between two adjacent color filters.

2. The image sensor of claim 1 , wherein a side surface of the upper grid portion has a first inclination,

a side surface of the lower grid portion has a second inclination, and

the second inclination is more perpendicular to a surface of the substrate than the second inclination.

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

side reflective layers formed on side surfaces of the grid patterns.

4. The image sensor of claim 3 , wherein the side reflective layers are in contact with the color filters.

5. The image sensor of claim 3 , wherein the side reflective layers have a smaller refractive index than that of the color filters.

6. The image sensor of claim 3 , wherein the top surface of the upper grid portion has substantially a same horizontal width as the side reflective layer.

7. The image sensor of claim 3 , wherein the side reflective layer has vertically flat side surfaces.

8. The image sensor of claim 3 , wherein the average horizontal thickness of the upper portion of the side reflective layer is smaller than the average horizontal thickness of the lower portion of the side reflective layer.

9. The image sensor of claim 3 , further comprising:

a coating layer formed in a liner shape on the top surface of the anti-reflective layer and the surfaces of the grid patterns.

10. The image sensor of claim 9 , wherein the side reflective layer has a lower refractive index than that of the coating layer.

11. The image sensor of claim 1 , wherein each of the isolation regions comprises a lower isolation region and an upper isolation region, and

the lower isolation region comprises an ion implanted region, and the upper isolation region comprises unit isolation regions formed in an isolation trench formed in the substrate.

12. The image sensor of claim 11 , wherein the unit isolation regions comprise an outer unit isolation region, a middle unit isolation region and an inner unit isolation region that are formed in the isolation trench, and

the outer unit isolation region covers the side surface of the middle unit isolation region, and the middle unit isolation region covers the side surface of the inner unit isolation region.

13. The image sensor of claim 12 , wherein the anti-reflective layer comprises a lower unit anti-reflective layer, a middle unit anti-reflective layer and an upper unit anti-reflective layer.

14. The image sensor of claim 13 , wherein the lower unit anti-reflective layer and the outer unit isolation region include a first material,

the middle unit anti-reflective layer and the middle unit isolation region include a second material, and

the upper unit anti-reflective layer and the inner unit isolation region include a third material.

15. An image sensor, comprising:

photoelectric conversion elements formed in a substrate, each photoelectric conversion element responsive to light to produce a photo sensing electrical signal;

isolation regions disposed between adjacent photoelectric conversion elements and configured to isolate the photoelectric conversion elements from one another;

an anti-reflective layer formed over the substrate to reduce an optical reflection to facilitate optical transmission of light incident to the photoelectric conversion elements through the anti-reflective layer;

grid patterns formed over the isolation regions to separate space above the photoelectric conversion elements;

color filters arranged between the grid patterns, each color filter structured to select a designated color in the incident light to transmit through a corresponding photoelectric conversion element; and

microlenses respectively formed over the color filters to direct incident light to the photoelectric conversion elements through the color filters,

wherein each of the grid patterns comprises an upper grid portion and a lower grid portion disposed below the upper grid portion, and

a bottom of the lower grid portion is embedded in the anti-reflective layer,

wherein a side surface of the upper grid portion has a first inclination,

a side surface of the lower grid portion has a second inclination, and

the second inclination is more perpendicular to a surface of the substrate than the second inclination.

16. An image sensor comprising:

photoelectric conversion elements formed in a substrate, each photoelectric conversion element responsive to light to produce a photo sensing electrical signal;

isolation regions disposed between adjacent photoelectric conversion elements and configured to isolate the photoelectric conversion elements from one another;

an anti-reflective layer formed over the substrate to reduce an optical reflection to facilitate optical transmission of light incident to the photoelectric conversion elements through the anti-reflective layer;

grid patterns formed over the isolation regions to separate space above the photoelectric conversion elements;

color filters arranged between the grid patterns, each color filter structured to select a designated color in the incident light to transmit through a corresponding photoelectric conversion element; and

microlenses respectively formed over the color filters to direct incident light to the photoelectric conversion elements through the color filters,

wherein each of the grid patterns comprises an upper grid portion and a lower grid portion disposed below the upper grid portion, and

a bottom of the lower grid portion is embedded in the anti-reflective layer,

wherein each of the isolation regions comprises a lower isolation region and an upper isolation region, and

the lower isolation region comprises an ion implanted region, and the upper isolation region comprises unit isolation regions formed in an isolation trench formed in the substrate.