Image sensor

1. A semiconductor device, comprising:

a semiconductor layer comprising a first surface and a second surface opposing the first surface;

a plurality of dielectric isolation features disposed within the semiconductor layer and adjacent the first surface of the semiconductor layer;

a plurality of metal isolation features extending from the second surface of the semiconductor layer;

a metal grid disposed directly over and in contact with the plurality of metal isolation features;

a plurality of microlens features disposed over the metal grid; and

a first dielectric layer extending continuously along the second surface of the semiconductor layer, between the semiconductor layer and the plurality of metal isolation features, and between each of the plurality of metal isolation features and one of the plurality of dielectric isolation features.

2. The semiconductor device of claim 1 , wherein the plurality of metal isolation features extend partially into the semiconductor layer.

3. The semiconductor device of claim 1 , wherein the plurality of metal isolation features extend completely through the semiconductor layer.

4. The semiconductor device of claim 1 , wherein the plurality of metal isolation features and the metal grid comprise aluminum.

5. The semiconductor device of claim 1 , wherein the plurality of metal isolation features terminate within the semiconductor layer without extending into the plurality of dielectric isolation features.

6. The semiconductor device of claim 1 , wherein the plurality of metal isolation features extend at least partially through the plurality of dielectric isolation features.

7. The semiconductor device of claim 1 , further comprising:

a second dielectric layer disposed between the first dielectric layer and the plurality of metal isolation features; and

a third dielectric layer disposed between the second dielectric layer and the plurality of metal isolation features,

wherein a composition of the first dielectric layer is different from a composition of the second dielectric layer and a composition of the third dielectric layer.

8. The semiconductor device of claim 7 ,

wherein the first dielectric layer comprises aluminum oxide, hafnium oxide, or a combination thereof,

wherein the second dielectric layer comprises tantalum oxide,

wherein the third dielectric layer comprises silicon oxide.

9. The semiconductor device of claim 7 , further comprising:

a top dielectric layer disposed over the plurality of metal isolation features and the third dielectric layer,

wherein the metal grid extends through the top dielectric layer to come in contact with the plurality of metal isolation features.

10. The semiconductor device of claim 7 , further comprising:

a color filter disposed between the semiconductor layer and the plurality of microlens features; and

a planarization layer disposed between the color filter and the plurality of microlens features.

11. An image sensor, comprising:

a first deep trench isolation (DTI) feature and a second DTI feature;

a photodetector disposed between the first DTI feature and the second DTI feature;

a metal grid disposed on and in direct contact with the first DTI feature and the second DTI feature; and

a bias source electrically coupled the metal grid,

wherein the first DTI feature, the second DTI feature and the metal grid comprise aluminum,

wherein the bias source and the metal grid are configured to apply a negative bias to the first DTI feature and the second DTI feature.

12. The image sensor of claim 11 , further comprising:

a semiconductor layer,

wherein the first DTI feature and the second DTI feature extend partially into the semiconductor layer,

wherein the semiconductor layer comprises a thickness between about 1.5 μm and about 50 μm.

13. The image sensor of claim 11 , further comprising:

a semiconductor layer,

wherein the first DTI feature and the second DTI feature extend completely into the semiconductor layer,

wherein the semiconductor layer comprises a thickness between about 1.5 μm and about 50 μm.

14. The image sensor of claim 11 , further comprising:

a first shallow trench isolation (STI) feature;

a second STI feature; and

a transistor disposed under the photodetector and between the first STI feature and the second STI feature,

wherein the first DTI feature is directly over the first STI feature and the second DTI feature is directly over the second STI feature.

15. The image sensor of claim 11 , further comprising:

at least one dielectric layer extending continuously from between sidewalls of the first DTI feature and the photodetector to over a top surface of the photodetector.

16. A structure, comprising:

a substrate;

a first deep trench isolation (DTI) feature and a second DTI feature extending into the substrate;

a metal oxide layer disposed between the first DTI feature and the substrate as well as between the second DTI feature and the substrate;

a metal grid disposed on and in direct contact with the first DTI feature and the second DTI feature; and

a first dielectric layer between the metal oxide layer and the first DTI feature as well as between the metal oxide layer and the second DTI feature,

wherein the first dielectric layer comprises tantalum oxide (Ta 2 O 5 ), titanium oxide, zirconium oxide, or a combination thereof.

17. The structure of claim 16 , wherein the first DTI feature, the second DTI feature and the metal grid comprise aluminum.

18. The structure of claim 16 , wherein the metal oxide layer comprises aluminum oxide, hafnium oxide, titanium oxide, barium titanate, zirconium oxide, lanthanum oxide, barium oxide, strontium oxide, yttrium oxide, or a combination thereof.

19. The structure of claim 16 , further comprising:

a second dielectric layer disposed over a top surface of the first dielectric layer,

wherein the second dielectric layer comprises silicon oxide.

20. The structure of claim 16 , further comprising:

a bias source electrically coupled the metal grid,

wherein the bias source and the metal grid are configured apply a negative bias to the first DTI feature and the second DTI feature.