BSI image sensor chips with separated color filters and methods for forming the same

1. A device comprising:

a semiconductor substrate having a front side and a backside;

a plurality of image sensors disposed at the front side of the semiconductor substrate;

a plurality of clear color-filters and a plurality of colored color-filters on the backside of the semiconductor substrate; and

a plurality of metal rings, each encircling one of the plurality of clear color-filters, wherein each of the plurality of metal rings comprises:

first edges contacting the respective encircled one of the clear color-filters, wherein the first edges are substantially vertical; and

second edges contacting colored color-filters, wherein the second edges are sloped, with portions of the second edges closer to the clear color-filters being higher than portions of the second edges closer to the colored color-filters.

2. The device of claim 1 , wherein the plurality of metal rings are interconnected to form a metal grid, and wherein the plurality of colored color-filters is disposed in grid openings of the metal grid.

3. The device of claim 1 , wherein the plurality of metal rings are spaced apart from each other, and wherein the plurality of colored color-filters is disposed in spaces between the plurality of metal rings.

4. The device of claim 3 , wherein the plurality of colored color-filters comprises red color-filters, green color-filters, and blue color-filters, and wherein the red color-filters are in contact with the green color-filters and the blue color-filters.

5. The device of claim 1 , wherein each of the clear color-filters overlaps one of the plurality of image sensors.

6. The device of claim 1 , wherein the plurality of metal rings comprises a metal selected from the group consisting essentially of tungsten, aluminum, silver, copper, and combinations thereof.

7. A device comprising:

a semiconductor substrate having a front side and a backside;

a plurality of image sensors disposed at the front side of the semiconductor substrate, wherein the plurality of image sensors forms an array;

a plurality of clear color-filters on the backside of the semiconductor substrate and over the semiconductor substrate, wherein each of the clear color-filters overlaps one of the plurality of image sensors;

a plurality of metal rings, each encircling one of the plurality of clear color-filters; and

a plurality of colored color-filters comprising red color-filters, green color-filters, and blue color-filters, wherein each of the colored color-filters overlaps one of the plurality of image sensors, wherein each of the plurality of metal rings comprises:

first edges contacting the clear color-filters, wherein the first edges are substantially vertical; and

second edges contacting the colored color-filters, wherein the second edges are sloped, with portions of the second edges closer to the clear color-filters being higher than portions of the second edges closer to the colored color-filters.

8. The device of claim 7 , wherein the plurality of metal rings are spaced apart from each other, and wherein spaces between the plurality of metal rings are filled with the plurality of colored color-filters.

9. The device of claim 7 , wherein the plurality of metal rings are interconnected to form a metal grid, and wherein each of the colored color-filters is disposed in one grid opening of the metal grid.

10. The device of claim 9 further comprising an additional metal grid underlying the metal grid, and between the metal grid and the semiconductor substrate.

11. The device of claim 7 , wherein the plurality of metal rings comprises a metal selected from the group consisting essentially of tungsten, aluminum, silver, copper, and combinations thereof.

12. A device comprising: a semiconductor substrate; a plurality of image sensors disposed in the semiconductor substrate; a plurality of colored color-filters aligned to the plurality of image sensors; a plurality of clear color-filters aligned to the plurality of image sensors; and a plurality of metal features separating the plurality of colored color-filters and the plurality of clear color-filters from each other, wherein each of the plurality of metal features comprises: first edges wherein the first edges are substantially vertical; and second edges opposite to respective first edges, wherein the second edges are sloped.

13. The device of claim 12 , wherein the plurality of colored color-filters comprises a plurality of red color-filters, a plurality of green color-filters, and a plurality of blue color-filters.

14. The device of claim 13 , wherein each of the plurality of red color-filters comprises a first edge in contact with an edge of one of the plurality of green color-filters, and a second edge in contact with an edge of one of the plurality of blue color-filters.

15. The device of claim 13 , wherein each of the plurality of red color-filters, the plurality of green color-filters, and the plurality of blue color-filters is encircled by one of the plurality of metal features.

16. The device of claim 12 , wherein each of the plurality of clear color-filters is encircled by one of the plurality of metal features.

17. The device of claim 12 , wherein the plurality of metal features is interconnected to form a metal grid, with the plurality of color-filters inside grid openings of the grid.

18. The device of claim 12 , wherein the plurality of metal features comprises tungsten, aluminum, or copper.

19. The device of claim 12 , wherein the first edges are in contact with the clear color-filters, and the second edges are in contact with the colored color-filters.

20. The device of claim 19 , wherein portions of the second edges closer to the clear color-filters are higher than portions of the second edges closer to the colored color-filters.