CMOS imager pixel designs with storage capacitor
View Patent ↗A charge storage capacitor which is connected to various light sensitive and/or electrical elements of a CMOS imager, as well as methods of formation, are disclosed. The charge storage capacitor may be formed entirely over a field oxide region of the CMOS imager, entirely over an active area of a pixel sensor cell, or partially over a field oxide region and partially over an active pixel area of a pixel sensor cell.
1. A pixel sensor cell for use in a CMOS imaging device, said pixel sensor cell comprising:
a field oxide region formed in a substrate;
a doped layer of a first conductivity type formed in said substrate and adjacent said field oxide region;
a photosensor including a charge collection region formed in said doped layer; and
a charge storage capacitor having one electrode connected by an electrical contact to said charge collection region to store charge accumulated by said charge collection region, said charge storage capacitor overlying said field oxide region and wherein another electrode of said storage capacitor is connected to a gate of a transistor of said pixel sensor cell by another contact.
2. The pixel sensor cell according to claim 1 , wherein said storage capacitor is a trench capacitor.
3. The pixel sensor cell according to claim 1 , wherein said storage capacitor is a stacked capacitor.
4. The pixel sensor cell according to claim 1 , wherein said storage capacitor is a metal capacitor.
5. The pixel sensor cell according to claim 1 , wherein said storage capacitor is an HSG capacitor.
6. The pixel sensor cell according to claim 1 , wherein said storage capacitor is a container capacitor.
7. The pixel sensor cell according to claim 1 , wherein said storage capacitor is partially overlying said field oxide region.
8. The pixel sensor cell according to claim 1 , wherein said storage capacitor is partially overlying over an active area of said photosensor.
9. The pixel sensor cell according to claim 1 , wherein said storage capacitor is a flat plate capacitor.
10. The pixel sensor cell according to claim 9 , wherein said storage capacitor is a flat plate capacitor including a first electrode, a second electrode and a dielectric layer between said first and second electrodes.
11. The pixel sensor cell according to claim 10 , wherein said first and second electrodes are independently selected from the group consisting of doped polysilicon, hemispherical grained polysilicon, TiN, poly/WSix, polyTiSi 2 , and poly/WNx/W.
12. The pixel sensor cell according to claim 1 , wherein said transistor is a transfer transistor for transferring charge accumulated in a second doped region of said second conductivity type adjacent to said charge collection region, wherein the gate of said transfer transistor is formed adjacent said second doped region and said charge collection region.
13. The pixel sensor cell according to claim 1 , wherein said storage capacitor is connected to said charge collection region by a metal contact.
14. The pixel sensor cell according to claim 1 wherein said transistor is a reset transistor.
15. The pixel sensor cell according to claim 1 wherein said transistor is a row select transistor.
16. The pixel sensor cell according to claim 1 further comprising a diffusion region of said second conductivity type adjacent said transfer transistor.
17. The pixel sensor cell according to claim 1 wherein said transistor is a source follower transistor.
18. The pixel sensor cell according to claim 1 , wherein said transistor is a global shutter transistor.
19. The pixel sensor cell according to claim 1 , wherein said photosensor comprises a photogate.
20. The pixel sensor cell according to claim 1 , wherein said photosensor comprises a photodiode.
21. The pixel sensor cell according to claim 1 , wherein said photosensor comprises a photoconductor.
22. The pixel sensor cell according to claim 1 , wherein said another contact is a metal contact.