Elevated pocket pixels, imaging devices and systems including the same and method of forming the same
View Patent ↗An elevated photosensor for image sensors and methods of forming the photosensor. The photosensor may have light sensors having indentation features including, but not limited to, v-shaped, u-shaped, or other shaped features. Light sensors having such an indentation feature can redirect incident light that is not absorbed by one portion of the photosensor to another portion of the photosensor for additional absorption. In addition, the elevated photosensors reduce the size of the pixel cells while reducing leakage, image lag, and barrier problems.
1. A photosensor comprising:
an epitaxial doped region having a first conductivity type formed over a doped region of a substrate, wherein the substrate doped region is a second conductivity type;
a raised photosensitive region comprising a hydrogenated amorphous silicon material formed over the epitaxial doped region and having at least one indentation feature over the epitaxial doped region, wherein the photosensitive region is configured to redirect reflected light; and
an upper electrode overlying the at least one indentation feature of the hydrogenated amorphous silicon material, the upper electrode having a portion through which one portion of the photosensitive region redirects the reflected light to another portion of the photosensitive region.
2. The device of claim 1 , wherein the at least one indentation feature has at least one of a v-shaped configuration and a u-shaped configuration.
3. A photosensor comprising:
an epitaxial doped region having a first conductivity type formed over a doped region of a substrate, wherein the substrate doped region is a second conductivity type;
a raised photosensitive region comprising a hydrogenated amorphous silicon material formed over the epitaxial doped region and having at least one indentation feature over the epitaxial doped region, the hydrogenated amorphous silicon material being adapted to redirect reflected light from one portion of the photosensitive region to another portion of the photosensitive region; and
a color filter formed in the at least one indentation feature of the hydrogenated amorphous silicon material.
4. The device of claim 3 further comprising a microlens formed over the color filter.
5. The device of claim 1 further comprising a metal material formed between the hydrogenated amorphous silicon material and the epitaxial doped region, wherein the metal material is contoured to the at least one indentation feature of the hydrogenated amorphous silicon material.
6. The device of claim 1 , wherein the first conductivity type is p-type and the second conductivity type is n-type.
7. A method of forming a photosensor comprising the steps of:
providing a semiconductor substrate having a first doped region of a first conductivity type;
forming an epitaxial doped region of second conductivity over the first doped region;
forming a raised photosensitive region over the epitaxial doped region by:
forming a dielectric over the epitaxial doped region;
forming at least one trench in the dielectric; and
forming a hydrogenated amorphous silicon material over the dielectric, wherein the hydrogenated amorphous silicon material is contoured to the at least one trench.
8. The method of claim 7 , wherein the first conductivity type is n-type and the second conductivity type is p-type.
9. The method of claim 7 , wherein the at least one trench has at least one of a v-shaped configuration and u-shaped configuration.
10. The method of claim 7 further comprising forming an upper electrode over the hydrogenated amorphous silicon material, wherein the upper electrode is contoured to the at least one trench.
11. The method of claim 10 further comprising forming a metal material between the dielectric and the hydrogenated amorphous silicon material, wherein the metal material is contoured to the at least one trench.
12. The method of claim 7 further comprising forming a color filter in the at least one trench.
13. The method of claim 12 further comprising forming a microlens over the color filter.
14. A method of forming an imaging device comprising:
forming each of a plurality of photosensors by:
forming a first doped region of a first conductivity type in a substrate;
forming an epitaxial doped region of a second conductivity type over the first doped region;
forming a dielectric over the epitaxial doped region;
forming at least one trench in the dielectric to the epitaxial doped region; and
forming a hydrogenated amorphous silicon material over the dielectric and the at least one trench, wherein the hydrogenated amorphous silicon material is contoured to the at least one trench.
15. The method of claim 14 , wherein the at least one trench has at least one of a v-shaped configuration and u-shaped configuration.
16. The method of claim 14 further comprising forming an upper electrode over the hydrogenated amorphous silicon material, wherein the upper electrode is contoured to the at least one trench.
17. The method of claim 16 further comprising forming a metal material between the dielectric and the hydrogenated amorphous silicon material, wherein the metal material is contoured to the at least one trench.
18. The method of claim 14 , wherein the first conductivity type is n-type and the second conductivity type is p-type.
19. The method of claim 14 further comprising forming a color filter for each photosensor in the at least one trench of each photosensor.
20. The method of claim 19 further comprising forming a microlens over each color filter.
21. The photosensor of claim 1 comprising, wherein the portion of the upper electrode is a first portion, and wherein the upper electrode has a second portion through which the other portion of the photosensitive region receives the reflected light.
22. The photosensor of claim 1 comprising, wherein the portion of the upper electrode comprises indium tin oxide.