Image sensor and fabricating method thereof

1. An apparatus comprising:

a photo diode formed in a semiconductor substrate;

at least one intermetal dielectric layer formed over the semiconductor substrate, the at least one intermetal dielectric layer having a plurality of through holes formed over and corresponding to the photo diode; and

a dielectric medium filling each one of the plurality of a through-holes in said at least one intermetal dielectric layer.

2. The apparatus of claim 1 , wherein said dielectric medium has a refractive index higher than the refractive index of said at least one intermetal dielectric layer.

3. The apparatus of claim 1 , comprising a micro lens formed over said at least one intermetal dielectric layer, wherein a focal length of the micro lens is different than a height of the dielectric medium.

4. The apparatus of claim 1 , comprising a micro lens formed over said at least one intermetal dielectric layer, wherein a focal length of the micro lens is substantially the same as a height of the dielectric medium.

5. The apparatus of claim 3 , wherein a color filter is formed between the micro lens and the dielectric medium.

6. The apparatus of claim 1 , wherein the dielectric medium comprises a plurality of layers.

7. An apparatus comprising:

a photo diode formed in a semiconductor substrate;

at least one intermetal dielectric layer formed over the semiconductor substrate, the at least one intermetal dielectric layer having a plurality of through holes formed over and corresponding to the photo diode;

a dielectric medium filling each one of the plurality of through-holes in said at least one intermetal dielectric layer to contact the photo diode, wherein a width of the dielectric medium is greater in an upper portion of the dielectric medium than in a lower portion of the dielectric medium;

a color filter formed over and contacting the at least one intermetal dielectric layer and the dielectric medium; and

a micro lens formed over and contacting the color filter.

8. The apparatus of claim 7 , wherein said dielectric medium has a refractive index higher than the refractive index of said at least one intermetal dielectric layer.

9. The apparatus of claim 7 , wherein a focal length of the micro lens is different than a height of the dielectric medium.

10. The apparatus of claim 7 , wherein a focal length of the micro lens is substantially the same as a height of the dielectric medium.

11. The apparatus of claim 7 , wherein the dielectric medium comprises a plurality of layers.

12. A method comprising:

forming at least one photo diode in a semiconductor substrate;

forming at least one intermetal dielectric layer over said semiconductor substrate;

forming a plurality of through-holes in said at least one intermetal dielectric layer over and corresponding to each one of the at least one photo diode

filling the plurality of through-holes with a dielectric medium.

13. The method of claim 12 , wherein the dielectric medium has a higher refractive index than said at least one intermetal dielectric layer.

14. The method of claim 12 , wherein said filling the plurality of through-holes with the dielectric medium comprises deposition of the dielectric medium.

15. The method of claim 12 , wherein said filling the plurality of through-holes with the dielectric medium comprises coating the dielectric medium.

16. The method of claim 12 , wherein a width of each of the plurality of through-holes is greater in an upper portion of the through-hole than in a lower portion of the through-hole.

17. The method of claim 12 , comprising:

forming a color filter over said at least one intermetal dielectric layer; and

forming a micro lens over the color filter.

18. The method of claim 17 , wherein the focal length of the micro lens is different than a length of each of the plurality of through-holes.

19. The method of claim 17 , wherein the focal length of the micro lens is the same as a length of each of the plurality of through-holes.