Photon guiding structure and method of forming the same
A photon guiding structure for reducing optical crosstalk in an image sensor and method of forming the same. The method includes forming a trench within an interlayer dielectric region formed over a photo-conversion device. The trench is formed such that it is vertically aligned with and has a horizontal cross-sectional shape similar to that of the photo-conversion device. A material is formed within the trench and a dielectric is formed over the material. The lined trench causes photons to strike the proper photo-conversion device and, as such, reduces the chance that photons will impinge upon neighboring photo-conversion devices.
1 . A pixel cell comprising:
a photo-conversion device formed in association with a substrate;
an interlayer dielectric region over said photo-conversion device; and
a photon guiding structure formed over said photo-conversion device and within said interlayer dielectric region, said structure comprising:
a trench formed within at least a portion of said interlayer dielectric region;
a material formed along a sidewall of said trench for internally reflecting photons down said photon guiding structure;
a dielectric formed over said material; and
an optically transparent material formed over said dielectric and filling a remaining portion of said trench.
2 . The pixel cell of claim 1 , wherein said trench is substantially vertically aligned with said photo-conversion device.
3 . The pixel cell of claim 2 , wherein cross-sectional shapes of said trench and said photo-conversion device are approximately the same.
4 . The pixel cell of claim 2 , wherein said trench has a circular cross-sectional shape.
5 . The pixel cell of claim 1 , wherein said material comprises at least one of aluminum, copper, silver, tungsten, titanium, gold, silicon nitride, titanium oxide or titanium nitride.
6 . The pixel cell of claim 1 , wherein a thickness of said material is between approximately 50 Å and approximately 1000 Å.
7 . The pixel cell of claim 1 , wherein said dielectric comprises at least one of TEOS, un-doped silicate glass or silicon nitride.
8 . The pixel cell of claim 1 , wherein a thickness of said dielectric is between approximately 50 Å and approximately 1000 Å.
9 . The pixel cell of claim 1 , wherein said optically transparent material comprises at least one of undoped silicate glass, spin-on dielectric, optically-transparent flowable oxide or photoresist.
10 . The pixel cell of claim 1 , wherein said interlayer dielectric region comprises one or more of interlayer dielectric layers, passivation layers, and metallization layers.
11 . An image sensor comprising:
an array of pixel cells, each said pixel cell comprising:
a photodiode formed in association with a substrate;
a trench formed in an interlayer dielectric region, said trench being over said photodiode and substantially vertically aligned with said photodiode;
a material formed along a sidewall of said trench for internally reflecting photons down said trench;
a dielectric formed over said material; and
an optically transparent material filling a remaining portion of said trench; and
a readout circuit for reading signals from said array of pixel cells.
12 . The image sensor of claim 11 , wherein said material comprises at least one of aluminum, copper, silver, tungsten, titanium, gold, silicon nitride, titanium oxide or titanium nitride.
13 . The image sensor of claim 11 , wherein said dielectric comprises at least one of TEOS, un-doped silicate glass or silicon nitride.
14 . The image sensor of claim 11 , wherein said optically transparent material comprises at least one of undoped silicate glass, spin-on dielectric, optically-transparent flowable oxide or photoresist.
15 . The image sensor of claim 11 , wherein a thickness of said dielectric is between approximately 50 Å and approximately 1000 Å.
16 . A system comprising:
a processor; and
an image sensor coupled to said processor, said image sensor comprising an array of pixel cells, each said pixel cell comprising:
a photo-conversion device formed on a substrate,
a trench formed over said photo-conversion device, wherein horizontal cross-sectional shapes of said trench and said photo-conversion device are approximately the same,
a material formed along a sidewall of said trench,
a dielectric formed over said material, and
an optically transparent material filling a remaining portion of said trench.
17 . The system of claim 16 , wherein said trench is substantially vertically aligned with said photo-conversion device.
18 . The system of claim 16 , wherein said material comprises at least one of aluminum, copper, silver, tungsten, titanium, gold, silicon nitride, titanium oxide or titanium nitride.
19 . The system of claim 16 , wherein said dielectric comprises at least one of TEOS, un-doped silicate glass or silicon nitride.
20 . The system of claim 16 , wherein said optically transparent material comprises at least one of undoped silicate glass, spin-on dielectric, optically-transparent flowable oxide or photoresist.
21 . A method of forming a pixel cell, said method comprising:
forming a photo-conversion device on a substrate;
forming an interlayer dielectric region over said photo-conversion device; and
forming a structure over said photo-conversion device and within said interlayer dielectric region, the act of forming said structure comprising:
forming a trench within at least a portion of said interlayer dielectric region,
forming a material along a sidewall of said trench,
forming a dielectric over said material, and
forming an optically transparent material over said dielectric to fill a remaining portion of said trench.
22 . The method of claim 21 , wherein said trench is substantially vertically aligned with said photo-conversion device.
23 . The method of claim 22 , wherein horizontal cross-sectional shapes of said trench and said photo-conversion device are approximately the same.
24 . The method of claim 22 , wherein said trench has a circular horizontal cross-sectional shape.
25 . The method of claim 21 , wherein a thickness of said material is between approximately 50 Å and approximately 1000 Å.
26 . The method of claim 21 , wherein a thickness of said dielectric is between approximately 50 Å and approximately 1000 Å.
27 . The method of claim 21 , wherein said material comprises at least one of aluminum, copper, silver, tungsten, titanium, gold, silicon nitride, titanium oxide or titanium nitride.
28 . The method of claim 21 , wherein said dielectric comprises at least one of TEOS, un-doped silicate glass or silicon nitride.
29 . The method of claim 21 , wherein said optically transparent material comprises at least one of undoped silicate glass, spin-on dielectric, optically-transparent flowable oxide or photoresist.
30 . The method of claim 21 further comprising forming a color filter array over said interlayer dielectric region.
31 . The method of claim 30 , wherein said trench extends from a level below said color filter array to a level above said photo-conversion device.
32 . A method of forming a photon guiding structure within a pixel cell of an image sensor, comprising:
forming an interlayer dielectric region over a photo-conversion device;
etching a trench into a portion of said interlayer dielectric region, said trench being substantially vertically aligned with said photo-conversion device;
forming a material along a sidewall of said trench;
forming a dielectric over said material; and
forming an optically transparent material over said dielectric to fill a remaining portion of said trench.
33 . The method of claim 32 , wherein horizontal cross-sectional shapes of said trench and said photo-conversion device are approximately the same.
34 . The method of claim 32 , further comprising planarizing a top portion of said structure to expose a top surface of said interlayer dielectric region.
35 . The method of claim 32 , further comprising forming a protective layer over said structure.
36 . The method of claim 32 , further comprising forming a color filter array over said structure.