Forming an imager array having improved color response
View Patent ↗CMOS image sensors have charge storage capacitors connected to various light sensitive and/or electrical elements. The capacity of the capacitors used for each pixel is tailored to the color to be detected. Charge storage capacitors may be formed entirely over a filed 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 method of forming an imager pixel array comprising the steps of:
forming at least three photosensors each responsive to a different color of light; and
forming a plurality of charge storage capacitors, each with different storage capacity respectively associated with one of said photosensors, a storage capacity of each said charge storage capacitor corresponding in proportion to a relative electron production capability of said respectively associated photosensor.
2. A method according to claim 1 , wherein a portion of said at least three photosensors is responsive to red color light, and said charge storage capacitor respectively associated with each said photosensor of said portion is formed with a storage capacity of between about 0 and about 20 femtofarads.
3. A method according to claim 1 , wherein a portion of said at least three photosensors is responsive to green color light, and said charge storage capacitor respectively associated with each said photosensor of said portion is formed with a storage capacity of between about 2 and about 20 femtofarads.
4. A method according to claim 1 , wherein a portion of said at least three photosensors is responsive to blue color light, and said charge storage capacitor respectively associated with each said photosensor of said portion is formed with a storage capacity of between about 3 and about 20 femtofarads.
5. A method according to claim 1 , wherein each said charge storage capacitor is formed as a flat plate capacitor.
6. A method according to claim 1 , further comprising forming a plurality of transfer transistors each in electrical communication with a respective one of said plurality of storage capacitors.
7. A method according to claim 1 , wherein the step of forming said plurality of charge storage capacitors comprises establishing electrical communication for receiving collected charges directly from said respectively associated photosensors.
8. A method according to claim 1 , wherein the step of forming said plurality of charge storage capacitors comprises establishing electrical communication for receiving collected charges from said respectively associated photosensors through a respective floating diffusion region which receives charges from said respectively associated respective one of said plurality of photosensors.
9. A method of forming an imager pixel array comprising the steps of:
providing a plurality of photosensors comprising at least a first portion responsive to a first color of light, a second portion responsive to a second color of light, and a third portion responsive to a third color of light; and
forming a plurality of storage capacitors, each with different storage capacity in electrical communication with a respective photosensor of said first, second, and third portions of said plurality of photosensors, a storage capacity of each said storage capacitor corresponding in proportion with a relative electron production capability of each said respective photosensor.
10. A method as in claim 9 , wherein the first color is red, a respective storage capacitor in electrical communication with a photosensor of said first portion having a storage capacity of between about 0 and about 20 femtofarads.
11. A method as in claim 9 , wherein the second color is green, and a respective storage capacitor in electrical communication with a photosensor of said second portion having a storage capacity of between about 2 and about 20 femtofarads.
12. A method as in claim 9 , wherein said third color of light is blue and a storage capacitor in electrical communication with a photosensor of said third portion has a storage capacity of between about 3 and about 20 femtofarads.
13. A method as in claim 9 , wherein the first color is red, a respective storage capacitor in electrical communication with a photosensor of said first portion having a storage capacity of between about 0 and about 20 femtofarads, the second color is green, and a respective storage capacitor in electrical communication with a photosensor of said second portion having a storage capacity of between about 2 and about 20 femtofarads, and said third color of light is blue and a storage capacitor in electrical communication with a photosensor of said third portion has a storage capacity of between about 3 and about 20 femtofarads.
14. A method of forming an imager pixel array comprising the steps of:
forming at least three photosensors each responsive to a different color of light; and
forming a plurality of charge storage capacitors, each with different storage capacity respectively associated with one of said photosensors, a storage capacity of each said charge storage capacitor corresponding in proportion to a relative electron production capability of said respectively associated photosensor, wherein a first portion of said at least three photosensors is responsive to red color light, and said charge storage capacitor respectively associated with each said photosensor of said first portion is formed with a storage capacity of between about 0 and about 20 femtofarads, a second portion of said at least three photosensors is responsive to green color light, and said charge storage capacitor respectively associated with each said photosensor of said second portion is formed with a storage capacity of between about 2 and about 20 femtofarads, and a third portion of said at least three photosensors is responsive to blue color light, and said charge storage capacitor respectively associated with each said photosensor of said third portion is formed with a storage capacity of between about 3 and about 20 femtofarads.