Method and apparatus providing an optical guide for an imager pixel having a ring of air-filled spaced slots around a photosensor
View Patent ↗A device and method to provide an optical guide of a pixel to guide incoming light onto a photosensor of the pixel and to improve the optical crosstalk immunity of an image sensor. The optical guide consists of an optically reflecting barrier formed as a trench that mitigates against optical crosstalk. The optical guide is made of an air-filled ring of spaced slots. In another embodiment, the optical guide structure can be filled with a low dielectric material with an index of refraction that is less than the index of refraction of the material used for the surrounding layers.
1. A pixel comprising:
a photo-conversion device formed over a substrate;
a lens over said photo-conversion device;
a plurality of fabricated layers between said photo-conversion device and lens; and
an optical guide structure formed in at least a portion of said plurality of fabricated layers, said optical guide structure comprising:
a series of trenches formed within at least a portion of said plurality of fabricated layers to define said optical guide structure, wherein each of said series of trenches is separated from adjacent trenches by a non-trench region comprising of a material of said plurality of fabricated layers.
2. The pixel of claim 1 , wherein said series of trenches are gas filled.
3. The pixel of claim 2 , wherein said gas comprises air.
4. The pixel of claim 1 , wherein said series of trenches comprise a second material filling each of said series of trenches.
5. The pixel of claim 4 , wherein said second material has a low-dielectric constant less than 1.45.
6. The pixel of claim 4 , wherein said second material is a low-dielectric constant material comprising carbon doped silicon dioxides.
7. The pixel of claim 4 , wherein said second material is a low-dielectric constant material comprising fluorinated silica glass oxide.
8. The pixel of claim 1 , wherein said series of trenches and said non-trench regions are formed above said photo-conversion device and are in a continuous pattern which surrounds a lateral area of said photo-conversion device.
9. The pixel of claim 1 , wherein each of said non-trench regions have a physical geometry distance between trench regions that is smaller than a predetermined wavelength of light associated with said photo-conversion device.
10. The pixel of claim 1 , wherein said series of trenches and said non-trench regions extend from a level below a level of said lens to a level above said substrate.
11. The pixel of claim 1 , wherein said photo-conversion device is a photosensor.
12. The pixel of claim 1 , wherein said photo-conversion device is a photo emitter.
13. The pixel of claim 1 , wherein said photo-conversion device is formed at least partially above said substrate.
14. The pixel of claim 13 , wherein said photo-conversion device above said substrate is an epitaxial layer.
15. A pixel comprising:
a photo-conversion device formed over a substrate;
a lens over said photo-conversion device;
a plurality of fabricated layers between said photo-conversion device and lens; and
an optical guide structure formed in at least a portion of said plurality of fabricated layers, said optical guide structure comprising:
a series of trenches formed within at least a portion of said plurality of fabricated layers to define said optical guide structure, wherein each of said series of trenches is separated from adjacent trenches by a non-trench region comprising of a material of said plurality of fabricated layers;
wherein said series of trenches are air gaps and each of said non-trench regions have a physical geometry distance between trench regions that is smaller than a predetermined wavelength of light associated with said photo-conversion device.
16. The pixel of claim 15 , wherein said series of trenches and said non-trench regions extend from a level below a level of said lens to a level above said substrate.
17. The pixel of claim 15 , wherein said photo-conversion device is a photosensor.
18. The pixel of claim 15 , wherein said photo-conversion device is a photo emitter.
19. The pixel of claim 15 , wherein said series of trenches and said non-trench regions are formed above said photo-conversion device and are in a continuous pattern which surrounds a lateral area of said photo-conversion device.
20. The pixel of claim 15 , wherein said photo-conversion device is formed at least partially above said substrate.
21. The pixel of claim 20 , wherein said photo-conversion device above said substrate is an epitaxial layer.
22. An image sensor comprising:
at least one pixel comprising:
a photo-conversion device;
a lens for receiving incident light;
a plurality of fabricated layers between said lens and photo-conversion device, said lens and photo-conversion device defining an optical path through said plurality of fabricated layers; and
an optical guide structure comprising:
a series of trenches formed within at least a portion of said plurality of fabricated layers to define said optical guide structure, wherein each of said series of trenches is separated from adjacent trenches by a non-trench region comprising of a material of said plurality of fabricated layers.
23. The image sensor of claim 22 , wherein each of said series of trenches and said non-trench regions are formed above said photo-conversion device and are in a continuous pattern which surrounds a lateral area of said photo-conversion device.
24. The image sensor of claim 22 , wherein said series of trenches are gas filled.
25. The image sensor of claim 22 , wherein said gas comprises air.
26. The image sensor of claim 22 , wherein said series of trenches comprise a second material filling each of said series of trenches.
27. The image sensor of claim 26 , wherein said second material has a low-dielectric constant less than 1.45.
28. The image sensor of claim 22 , wherein each of said non-trench regions have a physical geometry distance that is smaller than a predetermined wavelength of light associated with said photo-conversion device.
29. The image sensor of claim 22 , wherein each of said series of trenches and said non-trench regions extend from a level below a level of said lens to a level above said substrate.
30. The image sensor of claim 22 , wherein said photo-conversion device is a photosensor.
31. The image sensor of claim 22 , wherein said photo-conversion device is a photo emitter.
32. The image sensor of claim 22 , wherein said photo-conversion device is formed at least partially above said substrate.
33. The image sensor of claim 32 , wherein said photo-conversion device above said substrate is an epitaxial layer.
34. A system comprising:
a processor coupled to a image sensor, said image sensor comprising:
a photo-conversion device;
a lens for receiving incident light;
a plurality of fabricated layers between said lens and photo-conversion device, said lens and photo-conversion device defining an optical path through said plurality of fabricated layers; and
an optical guide structure comprising:
a series of trenches formed within at least a portion of said plurality of fabricated layers to define said optical guide structure, wherein each of said series of trenches is separated from adjacent trenches by a non-trench region comprising of a material of said plurality of fabricated layers.
35. The system of claim 34 , wherein said series of trenches are air gaps.
36. The system of claim 34 , wherein said series of trenches and said non-trench regions are formed above said photo-conversion device and are in a continuous pattern which surrounds a lateral area of said photo-conversion device.
37. The system of claim 34 , wherein said series of trenches are filled with a second material filling said series of trenches and said second material has a low-dielectric constant less than 1.45.
38. The system of claim 34 , wherein each of said non-trench regions have a physical geometry distance that is smaller than a predetermined wavelength of light associated with said photo-conversion device.
39. The system of claim 34 , wherein said photo-conversion device is formed at least partially above said substrate and said photo-conversion device above said substrate is an epitaxial layer.
40. A CMOS image sensor comprising:
an array of CMOS image pixel cells arranged in rows and columns formed over a substrate, each image pixel cell comprising:
a photosensitive region; and
a lens for receiving incident light;
a plurality of fabricated layers between said lens and photosensitive region device, said lens and photosensitive region device defining an optical path through said plurality of fabricated layers; and
an optical guide structure comprising:
a series of trenches formed within at least a portion of said plurality of fabricated layers to define said optical guide structure, wherein each of said series of trenches is separated from adjacent trenches by a non-trench region comprising of a material of said plurality of fabricated layers.
41. The CMOS image sensor of claim 40 , wherein said series of trenches are air-gaps.
42. The CMOS image sensor of claim 40 , wherein said series of trenches are filled with a second material filling said series of trenches, said second material has a low-dielectric constant less than 1.45.
43. The CMOS image sensor of claim 40 , wherein said series of trenches and said non-trench regions are formed above said photosensitive region and are in a continuous pattern which surrounds a lateral area by said photosensitive region.
44. The CMOS image sensor of claim 40 , wherein each of said non-trench regions have a physical geometry distance that is smaller than a predetermined wavelength of light associated with said photosensitive region.
45. The CMOS image sensor of claim 40 , wherein said photo-conversion device is formed at least partially above said substrate and said photo-conversion device above said substrate is an epitaxial layer.
46. An imager system comprising:
a processor; and
an imaging device electrically coupled to the processor, the imaging device comprising a CMOS pixel array, at least one pixel of the array comprising:
a photosensor formed in substrate;
a lens for receiving incident light;
a plurality of fabricated layers between said lens and photosensor, said lens and photosensor defining an optical path through said plurality of fabricated layers; and
an optical guide structure comprising:
a series of trenches formed within at least a portion of said plurality of fabricated layers to define said optical guide structure, wherein each of said series of trenches is separated from adjacent trenches by a non-trench region comprising of a material of said plurality of fabricated layers.
47. A method of forming an optical guide structure within a pixel cell of an imaging device, comprising the steps of:
forming a photo-conversion device in a substrate;
forming a plurality of fabricated layers over said photo-conversion device; and
etching a series of trenches into said dielectric layer, leaving a series of non-trench regions in the formed plurality of fabricated layers.
48. The method of claim 47 , wherein leaving each of said non-trench regions leaves a physical geometry distance that is smaller than a predetermined wavelength of light associated with said photo-conversion device.
49. The method of claim 47 , wherein said etching step comprises etching the series of trenches to surround a lateral area by said photo-conversion device leaving non-trench regions between each pair of trenches.
50. The method of claim 47 , wherein said etching step comprises etching the series of trenches from a level below a level of a lens formed above said plurality of fabricated layers, to a level above said substrate.
51. The method of claim 47 , wherein said filling step further comprises filling said trench with a second material having a lower refractive index.
52. The method of claim 47 , wherein said etching steps comprises etching said series of trenches and series of non-trench regions from a level below a level of a lens formed above said plurality of fabricated layers, to a level above said substrate.
53. The method of claim 47 , further comprising the step of growing an eptitaxial layer in contact with the top surface of said substrate.
54. A method of forming an optical guide structure within a CMOS image pixel cell of an imaging device, comprising the steps of:
forming a photosensor in a substrate;
forming a plurality of fabricated layers over said photosensor; and
etching a series of trenches into said dielectric layer, leaving a series of non-trench regions in the formed plurality of fabricated layers, wherein each of said non-trench regions leaves a physical geometry distance that is smaller than a predetermined wavelength of light associated with said photosensor.
55. The method of claim 54 , further comprising the step of growing an eptitaxial layer in contact with the top surface of said substrate.