Image sensor and method for fabricating same

1. A method for fabricating an image sensor, the method comprising:

forming a first doping region, wherein a top surface of the first doping region abuts an epitaxial layer; and

forming a second doping region a location of the epitaxial layer for a photodiode;

wherein the first doping region is located below and separated from the second doping region;

wherein the epitaxial layer includes a first conductivity type;

wherein the first doping region and the second doping region include a second conductivity type; and

wherein a doping concentration of the first doping region is lower than a doping concentration of the second doping region.

2. The method of claim 1 , wherein said forming a first doping region is performed before said forming a second doping region.

3. The method of claim 1 , wherein:

said forming a first doping region comprises using an ion implantation mask; and

said forming a second doping region comprises using the same ion implantation mask.

4. The method of claim 1 , wherein said forming a first doping region comprises implanting ions into the epitaxial layer.

5. The method of claim 4 , wherein said implanting ions comprises implanting phosphine ions at an energy of at least 500 KeV.

6. The method of claim 4 , wherein said implanting ions comprises implanting phosphine ions at an energy between approximately 500 KeV to approximately 1.5 MeV.

7. The method of claim 6 , wherein said implanting ions comprises implanting phosphine ions at a dose of between approximately 1×10 9 ions/cm 2 to approximately 5×10 11 ions/cm 2 .

8. A method for fabricating an image sensor, the method comprising:

forming a first doping region, wherein a top surface of the first doping region abuts an epitaxial layer; and

forming a photodiode in the epitaxial layer;

wherein the first doping region is located below and separated from the photodiode;

wherein the epitaxial layer includes a first conductivity type;

wherein the first doping region includes a second conductivity type; and

wherein the first doping region extends a depletion region of the photodiode.

9. The method of claim 8 , wherein:

said forming a photodiode comprises forming a second doping region;

the second doping region includes the second conductivity type; and

a doping concentration of the first doping region is lower than a doping concentration of the second doping region.

10. The method of claim 9 , wherein:

said forming a first doping region comprises using an ion implantation mask; and

said forming a second doping region comprises using the same ion implantation mask.

11. The method of claim 8 , wherein said forming a first doping region comprises implanting ions into the epitaxial layer.

12. The method of claim 11 , wherein said implanting ions comprises implanting phosphine ions at an energy of at least 500 KeV.

13. The method of claim 11 , wherein said implanting ions comprises implanting phosphine ions at an energy between approximately 500 KeV to approximately 1.5 MeV.

14. The method of claim 13 , wherein said implanting ions comprises implanting phosphine ions at a dose of between approximately 1×10 9 ions/cm 2 to approximately 5×10 11 ions/cm 2 .

15. A method for fabricating an image sensor, the method comprising:

forming a first doping region, wherein a top surface of the first doping region abuts an epitaxial layer; and

forming, in the epitaxial layer, a photodiode including a second doping region;

wherein the first doping region is located below and separated from the photodiode;

wherein the epitaxial layer includes a first conductivity type;

wherein the first doping region includes a second conductivity type; and

wherein the first doping region extends a depletion region of the photodiode.

16. The method of claim 15 , wherein said forming a first doping region is performed before said forming a photodiode.

17. The method of claim 15 , wherein:

said forming a first doping region comprises using an ion implantation mask; and

said forming a photodiode comprises using the same ion implantation mask to form the second doping region.

18. The method of claim 15 , wherein said forming a first doping region comprises implanting phosphine ions into the epitaxial layer at an energy of at least 500 KeV.

19. The method of claim 15 , wherein said forming a first doping region comprises implanting phosphine ions into the epitaxial layer at an energy between approximately 500 KeV to approximately 1.5 MeV.

20. The method of claim 19 , wherein said implanting phosphine ions comprises implanting phosphine ions at a dose of between approximately 1×10 9 ions/cm 2 to approximately 5×10 11 ions/cm 2 .

21. A method for fabricating an image sensor, the method comprising:

forming a first doping region within an epitaxial layer; and

forming a photodiode above the first doping region, wherein the photodiode includes a second doping region and a third doping region above the second doping region;

wherein the first doping region is located below and separated from the second doping region;

wherein the epitaxial layer and the third doping region include a first conductivity type;

wherein the first doping region and the second doping region include a second conductivity type;

wherein a doping concentration of the third doping region is greater than a doping concentration of the second doping region; and

wherein a doping concentration of the first doping region is lower than the doping concentration of the second doping region.

22. The method of claim 21 , wherein said forming a first doping region is performed before said forming a second doping region.

23. The method of claim 21 , wherein:

said forming a first doping region comprises using an ion implantation mask; and

said forming a second doping region comprises using the same ion implantation mask.

24. The method of claim 21 , wherein said forming a first doping region comprises implanting ions into the epitaxial layer.