Structure of dielectric grid with a metal pillar for semiconductor device

1. An image sensor device comprising:

a substrate having a front surface and a back surface;

a plurality of sensor elements disposed within the substrate, each of the plurality of sensor elements being operable to sense radiation projected towards the back surface of the substrate;

a dielectric grid disposed over the back surface of the substrate, the dielectric grid including:

a first dielectric layer as a bottom portion;

a metal pillar as a core portion of an upper portion, disposed over the first dielectric layer; and

a second dielectric layer wrapping around the metal pillar;

a stack of layers disposed over the back surface of the substrate, wherein at least one of the layers is positioned between dielectric grids; and

a color filter disposed on the dielectric grid such that a bottom of the color filter is below a top of the metal pillar.

2. The image sensor device of claim 1 , wherein the stack of layers comprises (from bottom to top);

an anti-reflection coating (ARC) layer over the back surface of the substrate;

an etch-stop-layer (ESL) over the ARC layer; and

a polymer layer over the ESL.

3. The image sensor device of claim 2 , wherein a refractive index of the polymer layer is substantially smaller than a refractive index of the ESL, which is substantially smaller than a refractive index of the ARC layer.

4. The image sensor device of claim 2 , wherein the dielectric grid is disposed over the ESI, wherein the polymer layer is disposed between dielectric grids.

5. The image sensor device of claim 1 , wherein the color filter aligns with a respective sensor element.

6. The image sensor device of claim 5 , wherein a refractive index of the color filter is substantially smaller than a refractive index of the top layer of the stack.

7. The image sensor device of claim 1 , further comprising:

a microlens disposed over the back surface of the substrate and aligned with the respective sensor element.

8. The image sensor device of claim 2 , further comprising:

a P+-type epitaxial layer under the ARC layer.

9. The image sensor device of claim 8 , wherein a refractive index of the P+-type epitaxial layer is substantially larger than a refractive index of the ARC layer.

10. The image sensor device of claim 1 , wherein the metal pillar includes metals from the group consisting of tungsten (W), aluminum (Al) and copper (Cu).

11. A device comprising:

a substrate having a front surface and a back surface;

a plurality of sensor elements disposed within the substrate, the plurality of sensor elements being operable to sense radiation projected towards the back surface of the substrate;

a dielectric grid disposed over the back surface of the substrate, wherein the dielectric grid includes:

a first dielectric layer as its bottom portion;

a metal pillar as its core portion of an upper portion; and

a second dielectric layer wrapping around the metal pillar;

a stack of layers disposed over the back surface of the substrate, including between dielectric grids; and

a plurality of color filters and microlenses disposed over the stack of layers and aligned with respective sensor elements, the color filters being positioned such that bottoms of the color filters are below a top of the metal pillar.

12. The device of claim 11 , wherein the stack of layers comprises (from bottom to top):

an anti-reflection coating (ARC) layer over the back surface of the substrate;

an etch-stop-layer (ESL) over the ARC layer; and

a polymer layer over the ESL, including between the dielectric grids.

13. The device of claim 1 , wherein the color filter is disposed over the stack of layers and the dielectric grid.

14. The device of claim 13 , wherein a refractive index of the color filter is substantially smaller than the refractive index of the top layer of the stack of layers.

15. The device of claim 13 , wherein the microlenses are disposed over the color filters.

16. The device of claim 11 , wherein the metal pillar includes metals from the group consisting of tungsten (W), aluminum (Al) and copper (Cu).

17. A device comprising:

a substrate having a front surface and a back surface, wherein a plurality of sensor elements are disposed within the substrate, each of the plurality of sensor elements being operable to sense radiation projected towards the back surface of the substrate;

a first dielectric layer over the back surface of the substrate;

a metal pillar over the first dielectric layer; and

a second dielectric layer over the metal pillar and the first dielectric layer, wherein the second and first dielectric layers form a dielectric grid, including wrapping around the metal pillar;

a polymer layer between dielectric grids; and

a color filter over the polymer layer, the color filter positioned such that a bottom of the color filter is lower than a top of the metal pillar.

18. The device of claim 17 , wherein the color filter has a refractive index smaller than a refractive index of the polymer layer.

19. The device of claim 18 , further comprising:

a lens over the polymer layer.

20. The device of claim 17 , further comprising:

a p + -type epitaxial layer over the back surface of the substrate;

an etch stop layer (ESL) over the back surface of the substrate; and

an anti-reflection coating (ARC) layer between the p + -type epitaxial layer and the ESL, wherein the p + -type epitaxial layer is chosen to have a refractive index larger than the ARC layer, wherein the ARC layer is chosen to have a refractive index larger than the ESL.