Image sensor including laser shield pattern

1. An image sensor comprising:

a substrate comprising a plurality of unit pixels;

a photodiode and an element isolation layer in the substrate;

an interconnection structure on a first surface of the substrate;

a stack structure on a second surface of the substrate; and

a grid pattern between ones of the plurality of unit pixels on the stack structure,

wherein the grid pattern comprises a lower grid pattern and an upper grid pattern physically contacting the lower grid pattern, the lower grid pattern comprising lanthanum oxide (LaO), amorphous silicon (a-Si), or polysilicon (poly-Si) and the upper grid pattern comprising a conductive material.

2. The image sensor of claim 1 , wherein the lower grid pattern has a thickness of about 1 nm to about 20 nm.

3. The image sensor of claim 1 , wherein the upper grid pattern comprises a first upper grid pattern and a second upper grid pattern, each of the first and second upper grid patterns comprising a different material.

4. The image sensor of claim 3 , wherein the first upper grid pattern comprises a conductive material and the second upper grid pattern comprises a low refractive index (LRI) material.

5. The image sensor of claim 4 , wherein a refractive index of the LRI material of the second upper grid pattern is in a range of about 1.0 to about 1.3.

6. The image sensor of claim 1 , wherein the grid pattern further comprises a concave recess in a lower portion of a sidewall of the grid pattern.

7. The image sensor of claim 6 , wherein a shortest width between both sidewalls of the lower grid pattern is less than a shortest width between both sidewalls of the upper grid pattern.

8. The image sensor of claim 6 , wherein a bottom surface of the upper grid pattern is partially exposed through the recess.

9. The image sensor of claim 1 , wherein the stack structure comprises:

a first insulating layer in contact with the substrate, the first insulating layer comprising aluminum oxide (Al 2 O 3 );

an anti-reflective layer on the first insulating layer; and

a second insulating layer on the anti-reflective layer and comprising silicon oxide (SiO 2 ).

10. The image sensor of claim 9 , further comprising a protective layer on the second insulating layer and the grid pattern.

11. The image sensor of claim 10 , wherein the protective layer comprises aluminum oxide (AlO).

12. The image sensor of claim 10 , wherein a thickness of the protective layer is greater than or equal to a thickness of the lower grid pattern.

13. The image sensor of claim 10 , wherein the upper grid pattern comprises a central portion overlapping the lower grid pattern and an overhang extending from both sides of the central portion in a plan view thereof.

14. The image sensor of claim 13 , wherein the protective layer is in contact with a bottom surface of the overhang.

15. The image sensor of claim 13 , wherein the lower grid pattern is wet-etched by at least one of an HCl solution, a diluted sulfuric acid peroxide (DSP) solution, or a NH 4 OH solution.

16. An image sensor comprising:

a substrate comprising a photodiode in a pixel region and an optical black region adjacent the pixel region; and

an optical black pattern in the optical black region, the optical black pattern not vertically overlapping a photodiode in the pixel region in a cross-sectional view of the image sensor, the optical black pattern comprising first, second, and third black patterns that are sequentially stacked and comprise different materials,

wherein lower ends of sidewalls of the optical black pattern have concave recesses, respectively.

17. The image sensor of claim 16 , wherein the first black pattern comprises at least one of lanthanum oxide (LaO), amorphous silicon (a-Si), or polysilicon (poly-Si).

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

a pad region outside of the optical black region;

a via plug in the pad region and extending through the substrate; and

a stack structure over the pixel region, the optical black region, and the pad region.

19. The image sensor of claim 18 , wherein the via plug comprises:

an upper pad pattern comprising a core portion passing through the substrate and a pad portion horizontally extending an upper portion of the core portion, the upper portion of the core portion being at a higher position than the stack structure, such that the stack structure is between the upper portion of the core portion and the substrate; and

a lower pad pattern between the upper pad pattern and the stack structure.

20. The image sensor of claim 18 , wherein a concave recess is formed in lower ends of both sidewalls of the via plug on the stack structure.