Pixel cells in a honeycomb arrangement
The present invention, in the various exemplary embodiments, provides a RGB color filter array. The red, green and blue pixel cells are arranged in a honeycomb pattern. The honeycomb layout provides the space to vary the size of pixel cells of an individual color so that, for example, the photosensor of blue pixels can be made larger than that of the red or green pixels. In another aspect of the invention, depicted in the exemplary embodiments, the honeycomb structure can also be implemented with each pixel rowing having a same color of pixel cells which can simplify can conversion in the readout circuits. In another aspect of the invention, the RGB honeycomb pixel array may be implemented using a shared pixel cell architecture.
1. A method of fabricating an imager comprising:
fabricating an array of pixel cells in a honeycomb pattern in rows and columns, wherein each pixel cell has a color filter formed over a photosensor; and
fabricating shared pixel components comprising a combined charge collection region shared by at least four pixel cells from a first column of said array and two pixel cells from a second column of said array.
2. The method according to claim 1 , wherein said shared pixel components further comprise a reset transistor, a source follower transistor and a row select transistor.
3. The method according to claim 1 , further comprising the step of providing a transfer transistor for each of said pixel cells for transferring charge from the photosensor to the combined charge collection region.
4. The method according to claim 1 , wherein the act of fabricating said array of pixel cells further comprises:
fabricating a first plurality of the photosensors of pixel cells of a first color with a first predetermine size,
fabricating a second plurality of the photosensors of pixel cells of a second color with a second predetermined size, and
fabricating a third plurality of the photosensors of pixel cells of a third color with a third predetermined size,
wherein said first, second and third predetermined sizes may or may not be equal.
5. The method according to claim 1 , wherein said array includes blue, red, and green color pixels and the photosensors of a plurality of blue pixel cells are fabricated larger than the photo sensors of other color pixel cells.
6. The method according to claim 1 , wherein said array includes blue, red, and green color pixels and the photosensors of a plurality of green pixel cells are fabricated larger than the photosensors of other color pixel cells.
7. The method according to claim 1 , wherein the act of fabricating an array of pixel cells further comprises:
fabricating at least one red pixel cell;
fabricating at least one green pixel cell; and
fabricating at least one blue pixel cell,
wherein the ratio of the red, green and blue pixel cells in said array is about 1:1:1.
8. The method according to claim 1 , wherein each pixel cell in a row of said array of pixels has said color filter formed of the same color.
9. The method according to claim 1 , wherein the combined charge collection region is formed of two charge collection regions, each charge collection region is shared by at least two pixel cells from the first column of said array and one pixel cell from the second column of said array.
10. The method according to claim 2 , wherein said shared pixel components shared by said at least four pixel cells from said first column and said two pixel cells from said second adjacent column of said array comprise a single reset transistor, a single source follower transistor and a single row select transistor.
11. A method of forming a CMOS imager comprising the steps of:
fabricating an array of CMOS pixel cells in a honeycomb pattern in rows and columns, wherein each pixel cell has a color filter, of one of three colors, formed over a photo sensor;
fabricating shared pixel components comprising a reset transistor, a source follower transistor and a row select transistor, wherein said shared pixel components are shared by at least two pixel cells from a first column of said array and a pixel cell from an adjacent second column of said array; and
arranging said shared pixel components to form a L-shaped readout trunk for promoting an efficient use of space.
12. The method according to claim 11 , wherein said shared pixel components further comprise a charge collection region.
13. The method according to claim 11 , wherein said shared pixel components are shared by at least 3 pixel cells.
14. The method according to claim 11 , wherein said shared pixel components are shared by at least 6 pixel cells.
15. The method according to claim 12 , further comprising the step of providing a transfer transistor for each of said pixel cells for transferring charge from the photosensor to said charge collection region.
16. The method according to claim 11 , wherein the act of fabricating said array of CMOS pixel cells further comprises:
fabricating a first plurality of the photosensors with a first predetermine size,
fabricating a second plurality of the photosensors with a second predetermined size, and
fabricating a third plurality of the photosensors with a third predetermined size,
wherein said first, second and third predetermined sizes may or may not be equal.
17. The method according to claim 11 , wherein each pixel cell in a row of said array of pixels has said color filter formed of the same color.
18. A method of forming a CMOS imager comprising the steps of:
fabricating an array of pixel cells in a honeycomb pattern in rows and columns, wherein each pixel cell has a color filter formed over a photosensor and the photosensors of said pixel cells of one color are formed larger than the photosensors of at least some of the remaining pixel cells; and
fabricating shared pixel components comprising an interconnected floating diffusion region, a reset transistor, a source follower transistor and a row select transistor, wherein said shared pixel components are shared by at least four pixel cells from a first column of said array and two pixel cells from a second adjacent column of said array.
19. The method according to claim 18 , further comprising the step of providing a transfer transistor for each of said pixel cells for transferring charge from the photosensor to the interconnected floating diffusion region.
20. The method according to claim 18 , wherein the step of fabricating said array of pixel cells further comprises:
fabricating a first plurality of the photosensors with a first predetermine size,
fabricating a second plurality of the photosensors with a second predetermined size, and
fabricating a third plurality of the photosensors with a third predetermined size.
21. The method according to claim 20 , wherein one of said first, second, and third plurality of photosensors are associated with blue pixel cells and are fabricated larger than the photo sensors associated with the remaining plurality of pixel cells.
22. The method according to claim 20 , wherein one of said first, second, and third plurality of photosensors are associated with green pixel cells and are fabricated larger than the photosensors associated with the remaining plurality of pixel cells.
23. The method according to claim 18 , wherein the interconnected floating diffusion region is formed of two floating diffusion regions, each floating diffusion region is shared by at least two pixel cells from the first column of said array and one pixel cell from the second column of said array.
24. The method according to claim 18 , wherein said shared pixel components shared by said at least four pixel cells from said first column and said two pixel cells from said second adjacent column of said array comprise a single reset transistor, a single source follower transistor and a single row select transistor.