Image sensor having micro-lens array separated with ridge structures and method of making

1. An image sensor comprising:

a plurality of pixels formed in a semiconductor substrate, each pixel including a light sensitive element;

a micro-lens over each of said light sensitive elements; and

a layer of oxide disposed between the light sensitive elements and the micro-lenses, wherein the layer of oxide includes a horizontal top surface and raised ridge structures formed from the layer of oxide extending above the horizontal top surface and surrounding each of said micro-lenses, wherein each said raised ridge structure has a triangular cross-section and at least partially supports said micro-lens, wherein the micro-lens overlays a base portion of the raised ridge structure such that a maximum width of the micro-lens is greater than a width of the micro-lens at the horizontal top surface of the layer of oxide.

2. The image sensor of claim 1 wherein said raised ridge structure is circular.

3. The image sensor of claim 1 wherein said raised ridge structure confines said micro-lens.

4. The image sensor of claim 1 wherein the micro-lenses are formed from polymethylmethacrylate (PMMA) or polyglycidylmethacrylate (PGMA).

5. The image sensor of claim 1 wherein said raised ridge structure has a height of about 0.2 microns.

6. The image sensor of claim 1 further including a color filter layer between said micro-lenses and said light sensitive elements.

7. A pixel of an image sensor comprising:

a light sensitive element formed in a semiconductor substrate;

a micro-lens over said light sensitive element; and

a layer of oxide disposed between the light sensitive element and the micro-lens, wherein the layer of oxide includes a horizontal top surface and a raised ridge structure formed from the layer of oxide extending above the horizontal top surface and surrounding said micro-lens, wherein said raised ridge structure has a triangular cross-section and at least partially supports said micro-lens, wherein the micro-lens overlays a base portion of the raised ridge structure such that a maximum width of the micro-lens is greater than a width of the micro-lens at the horizontal top surface of the layer of oxide.

8. The pixel of claim 7 wherein said raised ridge structure is circular.

9. The pixel of claim 7 wherein said raised ridge structure confines said micro-lens.

10. The pixel of claim 7 wherein the micro-lens is formed from polymethylmethacrylate (PMMA) of polyglycidylmethacrylate (PGMA).

11. The pixel of claim 7 wherein said raised ridge structure has a height of about 0.2 microns.

12. The pixel of claim 7 further including a color filter layer between said micro-lens and said light sensitive element.

13. A method of forming a pixel of an image sensor comprising:

forming a light sensitive element in a semiconductor substrate;

forming a top planarizing layer of oxide over said light sensitive element;

isotropically dry etching the top planarizing layer of oxide to form a horizontal top surface and a raised ridge structure from said top planarizing layer, said raised ridge structure extending above the horizontal top surface and encompassing said light sensitive element; and

forming a microlens within the interior of said raised ridge structure and over said light sensitive element, wherein said raised ridge structure has a triangular cross-section and at least partially supports said micro-lens, wherein the micro-lens overlays a base portion of the raised ridge structure such that a maximum width of the micro-lens is greater than a width of the micro-lens at the horizontal top surface of the layer of oxide.

14. The method claim 13 wherein said raised ridge structure confines said micro-lens.

15. The method of claim 13 wherein said raised ridge structure is a closed shape.

16. The method of claim 13 further including forming a color filter layer between said micro-lens and said light sensitive element.