Image sensor and method of fabricating the same

1 . An image sensor, comprising:

a substrate that has a first surface and a second surface opposite to the first surface;

a fixed charge layer in contact with the second surface;

an interlayer dielectric layer that covers the first surface;

a device isolation part adjacent to the first surface in the substrate, the device isolation part defining an active section in the substrate; and

a pixel isolation part in the substrate, the pixel isolation part penetrating the device isolation part and separating pixels from each other,

wherein the pixel isolation part includes

a conductive pattern in the substrate and in contact with the fixed charge layer,

a buried dielectric pattern between the conductive pattern and the interlayer dielectric layer, and

an isolation dielectric pattern that surrounds sidewalls of the conductive pattern and the buried dielectric pattern and is simultaneously in contact with the fixed charge layer and the interlayer dielectric layer,

wherein the isolation dielectric pattern has a first thickness at a level between the buried dielectric pattern and the conductive pattern, and

wherein the isolation dielectric pattern has a second thickness at a level of a bottom surface of the fixed charge layer, the second thickness being different from the first thickness.

2 . The image sensor of claim 1 , further comprising a transfer gate on the first surface,

wherein the second thickness is about 1.2 times to about 2 times the first thickness.

3 . The image sensor of claim 1 , wherein

the conductive pattern has a first sidewall,

the isolation dielectric pattern has a second sidewall, and

a slope of the first sidewall is different from a slope of the second sidewall.

4 . The image sensor of claim 1 , wherein

when viewed in plan, the conductive pattern has a network shape that surrounds each of the pixels,

the conductive pattern has a first portion adjacent to the first surface and a second portion adjacent to the second surface, and

the second portion of the conductive pattern has a convex segment and a concave segment between the pixels that are spaced apart from each other in a first direction, the first direction extending parallel to the second surface of the substrate.

5 . The image sensor of claim 4 , wherein

the convex segment of the second portion of the conductive pattern is spaced apart from a center of one of the pixels in the first direction, and

the concave segment of the second portion of the conductive pattern is adjacent to a corner of the one of the pixels.

6 . The image sensor of claim 1 , wherein the isolation dielectric pattern includes:

a first isolation dielectric pattern in contact with the substrate;

a second isolation dielectric pattern in contact with the conductive pattern; and

a third isolation dielectric pattern between the first isolation dielectric pattern and the second isolation dielectric pattern,

wherein a dielectric constant of the third isolation dielectric pattern is different from respective dielectric constants of the first and second isolation dielectric patterns.

7 . The image sensor of claim 6 , wherein the second isolation dielectric pattern has a third thickness adjacent to the first surface and a fourth thickness adjacent to the second surface, the fourth thickness being different from the third thickness.

8 . The image sensor of claim 1 , wherein

the conductive pattern has a hollow shell shape, and

the pixel isolation part further includes a dielectric pattern that fills an inner region of the conductive pattern.

9 . An image sensor, comprising:

a substrate that has a first surface and a second surface opposite to the first surface;

a fixed charge layer in contact with the second surface;

an interlayer dielectric layer that covers the first surface;

a device isolation part adjacent to the first surface in the substrate, the device isolation part defining an active section in the substrate; and

a pixel isolation part in the substrate, the pixel isolation part penetrating the device isolation part and separating pixels from each other,

wherein the pixel isolation part includes

a conductive pattern in the substrate and in contact with the fixed charge layer,

a buried dielectric pattern between the conductive pattern and the interlayer dielectric layer, and

an isolation dielectric pattern that surrounds sidewalls of the conductive pattern and the buried dielectric pattern and is simultaneously in contact with the fixed charge layer and the interlayer dielectric layer,

wherein the conductive pattern has a first sidewall,

wherein the isolation dielectric pattern has a second sidewall, and

wherein a slope of the first sidewall relative to a bottom surface of the fixed charge layer is different from a slope of the second sidewall relative to the bottom surface of the fixed charge layer.

10 . The image sensor of claim 9 , wherein the slope of the second sidewall is greater than the slope of the first sidewall.

11 . The image sensor of claim 9 , wherein

the isolation dielectric pattern has a first thickness at a level between the buried dielectric pattern and the conductive pattern, and

the isolation dielectric pattern has a second thickness at a level of the bottom surface of the fixed charge layer, the second thickness being different from the first thickness.

12 . The image sensor of claim 11 , further comprising a transfer gate on the first surface,

wherein the second thickness is about 1.2 times to about 2 times the first thickness.

13 . The image sensor of claim 9 , wherein

when viewed in plan, the conductive pattern has a network shape that surrounds each of the pixels,

the conductive pattern has a first portion adjacent to the first surface and a second portion adjacent to the second surface, and

the second portion of the conductive pattern has a convex segment and a concave segment between the pixels that are spaced apart from each other in a first direction.

14 . The image sensor of claim 13 , wherein

the convex segment of the second portion of the conductive pattern is spaced apart from a center of one of the pixels in the first direction, and

the concave segment of the second portion of the conductive pattern is adjacent to a corner of the one of the pixels.

15 . The image sensor of claim 9 , wherein the isolation dielectric pattern includes:

a first isolation dielectric pattern in contact with the substrate;

a second isolation dielectric pattern in contact with the conductive pattern; and

a third isolation dielectric pattern between the first isolation dielectric pattern and the second isolation dielectric pattern,

wherein a dielectric constant of the third isolation dielectric pattern is different from respective dielectric constants of the first and second isolation dielectric patterns.

16 . The image sensor of claim 15 , wherein

the conductive pattern has a hollow shell shape, and

the pixel isolation part further includes a dielectric pattern that fills an inner region of the conductive pattern.

17 . An image sensor, comprising:

a substrate that has a first surface and a second surface opposite to the first surface, the substrate including first to fourth pixels that are disposed along a clockwise direction;

a fixed charge layer in contact with the second surface;

a transfer gate on the first surface of the substrate on each of the first to fourth pixels;

an interlayer dielectric layer that covers the first surface of the substrate; and

a pixel isolation part in the substrate and between the first to fourth pixels, the pixel isolation part separating the first to fourth pixels from each other,

wherein the pixel isolation part includes

a conductive pattern in the substrate and in contact with the fixed charge layer,

a buried dielectric pattern between the conductive pattern and the interlayer dielectric layer, and

an isolation dielectric pattern that surrounds sidewalls of the conductive pattern and the buried dielectric pattern and is simultaneously in contact with the fixed charge layer and the interlayer dielectric layer,

wherein the isolation dielectric pattern has a first thickness at a level between the buried dielectric pattern and the conductive pattern,

wherein the isolation dielectric pattern has a second thickness at a level of a bottom surface of the fixed charge layer, and

wherein the second thickness is about 1.2 times to about 2 times the first thickness.

18 . The image sensor of claim 17 , wherein

the conductive pattern has a first sidewall,

the isolation dielectric pattern has a second sidewall, and

a slope of the first sidewall relative to the bottom surface of the fixed charge layer is less than a slope of the second sidewall relative to the bottom surface of the fixed charge layer.

19 . The image sensor of claim 17 , wherein

when viewed in plan, the conductive pattern has a network shape that surrounds each of the first to fourth pixels,

the conductive pattern has a first portion adjacent to the first surface and a second portion adjacent to the second surface, and

the second portion of the conductive pattern has a convex segment and a concave segment between ones of the first to fourth pixels, the ones of the first to fourth pixels being spaced apart from each other in a first direction.

20 . The image sensor of claim 19 , wherein

the convex segment of the second portion of the conductive pattern is spaced apart from a center of one of the first to fourth pixels in the first direction, and

the concave segment of the second portion of the conductive pattern is adjacent to a corner of the one of the first to fourth pixels.