Image sensor

1. An image sensor comprising:

a substrate having a first surface and a second surface opposite the first surface;

a plurality of conductive pads;

a first group of isolation structures including a first isolation structure; and

a second group of isolation structures including a second isolation structure and a third isolation structure,

wherein the first isolation structure comprises:

a first isolation trench in contact with the first surface;

a second isolation trench in contact with the second surface, the second isolation trench connected to a bottom of the first isolation trench; and

a first pattern in the second isolation trench and in contact with the second surface,

wherein a distance from the first surface to the bottom of the first isolation trench in a first direction is longer than a distance from the first surface to a bottom of the first pattern in the first direction,

wherein the bottom of the first isolation trench is spaced apart from the second surface and the bottom of the first pattern is spaced apart from the first surface,

wherein the first direction is perpendicular to the first surface,

wherein the first group of isolation structures is disposed in a central region of the substrate in a plan view,

wherein the second group of isolation structures is disposed adjacent to the plurality of conductive pads in the plan view,

wherein the second isolation structure has the same structure as the first isolation structure, and

wherein the image sensor is configured to receive light at the second surface.

2. The image sensor of claim 1 , wherein the bottom of the first pattern has an uneven shape.

3. The image sensor of claim 2 , wherein the second isolation structure is disposed at a first side of the central region,

wherein the third isolation structure is disposed at a second side of the central region, and

wherein the first side of the central region is opposite the second side of the central region.

4. The image sensor of claim 3 , wherein the first isolation structure further comprises a second pattern vertically overlapping with the first pattern in the first direction,

wherein the second pattern is in contact with the first surface,

wherein a bottom of the second pattern is spaced apart from the second surface, and

wherein the bottom of the second pattern has an uneven shape.

5. The image sensor of claim 4 , further comprising a sidewall insulating pattern in contact with the first pattern, and

wherein the sidewall insulating pattern is between the first pattern and an inner sidewall of the second isolation trench.

6. The image sensor of claim 5 , wherein the sidewall insulating pattern is in direct contact with the second surface.

7. The image sensor of claim 5 , further comprising a barrier region on the second isolation trench, and

wherein the barrier region is doped with P-type impurities.

8. The image sensor of claim 7 , wherein a width of the first isolation structure in a second direction on the first surface is equal to a width of the second isolation structure in the second direction on the first surface, and

wherein the second direction is parallel to the first surface.

9. The image sensor of claim 8 , wherein a width of the first isolation structure in the second direction on the second surface is equal to a width of the second isolation structure in the second direction on the second surface.

10. The image sensor of claim 8 , wherein the first pattern includes a lower dopant region and an upper dopant region,

wherein a dopant concentration of the upper dopant region is greater than a dopant concentration of the lower dopant region, and

wherein a distance from the first surface to the upper dopant region in the first direction is shorter than a distance from the second surface to the upper dopant region in the first direction.

11. An image sensor comprising:

a substrate having a first surface and a second surface opposite the first surface;

a plurality of conductive pads;

a first group of isolation structures including a first isolation structure; and

a second group of isolation structures including a second isolation structure and a third isolation structure,

wherein the first isolation structure comprises:

a first isolation trench in contact with the first surface;

a second isolation trench in contact with the second surface, the second isolation trench connected to a bottom of the first isolation trench; and

a first pattern in the second isolation trench and in contact with the second surface,

wherein the first pattern includes a lower dopant region and an upper dopant region,

wherein a dopant concentration of the upper dopant region is greater than a dopant concentration of the lower dopant region,

wherein the first group of isolation structures is disposed in a central region of the substrate in a plan view,

wherein the second group of isolation structures is disposed adjacent to the plurality of conductive pads in the plan view,

wherein the second isolation structure has the same structure as the first isolation structure, and

wherein the image sensor is configured to receive light at the second surface.

12. The image sensor of claim 11 , wherein the bottom of the first pattern has an uneven shape.

13. The image sensor of claim 12 , wherein the second isolation structure is disposed at a first side of the central region,

wherein the second isolation structure is disposed at a second side of the central region, and

wherein the first side of the central region is opposite to the second side of the central region.

14. The image sensor of claim 12 , further comprising a first barrier region on the first isolation structure and a second barrier region on the second isolation structure, and

wherein the first and second barrier regions are doped with P-type impurities.

15. The image sensor of claim 14 , further comprising an aluminum oxide layer disposed in direct contact with the first pattern.

16. The image sensor of claim 15 , wherein the aluminum oxide layer is on the second surface.

17. The image sensor of claim 15 , further comprising a second pattern vertically overlapping with the first pattern in the first direction,

wherein the second pattern is in contact with the first surface,

wherein a bottom of the second pattern is spaced apart from the second surface, and

wherein the bottom of the second pattern has an uneven shape.

18. The image sensor of claim 15 , wherein a width of the first isolation structure in a second direction on the first surface is equal to a width of the second isolation structure in the second direction on the first surface, and

wherein the second direction is parallel to the first surface.

19. An image sensor comprising:

a substrate having a first surface and a second surface opposite the first surface;

a conductive pad;

a first isolation structure in contact with the first and second surfaces;

a second isolation structure in contact with the first and second surfaces;

a first pattern in the first isolation structure; and

a second pattern in the second isolation structure,

wherein the first isolation structure is disposed in a central region of the substrate in a plan view,

wherein the second isolation structure is disposed between the central region and the conductive pad in the plan view,

wherein the second isolation structure has the same structure as the first isolation structure,

wherein a dopant concentration of the first pattern is different from a dopant concentration of the second pattern,

wherein the first pattern is in contact with the second surface and spaced apart from the first surface,

wherein the second pattern is in contact with the second surface and spaced apart from the first surface, and

wherein the image sensor is configured to receive light at the second surface.

20. The image sensor of claim 19 , wherein the first pattern includes a lower dopant region and an upper dopant region, and

wherein a dopant concentration of the upper dopant region is greater than a dopant concentration of the lower dopant region.