Method for forming a low leakage contact in a CMOS imager
First Claim
1. An imaging device comprising:
- a substrate;
a photosensitive area within said substrate for accumulating photo-generated charge in said area;
a floating diffusion region in said substrate for receiving charge from said photosensitive area, said floating diffusion region being doped to a first conductivity type at a first concentration;
a readout circuit comprising at least an output transistor formed in said substrate;
an insulating layer formed over said substrate;
a doped polysilicon conductor formed in said insulating layer for connecting said floating diffusion region with a gate of said output transistor, said doped polysilicon conductor being doped to said first conductivity type; and
a contact region between said doped polysilicon conductor and said floating diffusion region, said contact region being in diffusible communication with said polysilicon conductor, and said contact region comprising dopants of said first conductivity type at said first concentration, and diffused dopants of said first conductivity type from said doped polysilicon conductor.
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Accused Products
Abstract
An imaging device formed as a CMOS semiconductor integrated circuit includes a doped polysilicon contact line between the floating diffusion region and the gate of a source follower output transistor. The doped polysilicon contact line in the CMOS imager decreases leakage from the diffusion region into the substrate which may occur with other techniques for interconnecting the diffusion region with the source follower transistor gate. Additionally, the CMOS imager having a doped polysilicon contact between the floating diffusion region and the source follower transistor gate allows the source follower transistor to be placed closer to the floating diffusion region, thereby allowing a greater photo detection region in the same sized imager circuit.
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Citations
24 Claims
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1. An imaging device comprising:
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a substrate;
a photosensitive area within said substrate for accumulating photo-generated charge in said area;
a floating diffusion region in said substrate for receiving charge from said photosensitive area, said floating diffusion region being doped to a first conductivity type at a first concentration;
a readout circuit comprising at least an output transistor formed in said substrate;
an insulating layer formed over said substrate;
a doped polysilicon conductor formed in said insulating layer for connecting said floating diffusion region with a gate of said output transistor, said doped polysilicon conductor being doped to said first conductivity type; and
a contact region between said doped polysilicon conductor and said floating diffusion region, said contact region being in diffusible communication with said polysilicon conductor, and said contact region comprising dopants of said first conductivity type at said first concentration, and diffused dopants of said first conductivity type from said doped polysilicon conductor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An imaging device comprising
a semiconductor integrated circuit substrate; -
a photosensitive device formed on said substrate for accumulating photo-generated charge in an underlying region of said substrate;
a floating diffusion region in said substrate for receiving said photo-generated charge, said floating diffusion region being doped to a first conductivity type at a first dopant concentration, wherein said floating diffusion region comprises a second region of said first conductivity type at a second dopant concentration, said second dopant concentration being greater than said first dopant concentration;
a readout circuit comprising at least an output transistor formed in said substrate;
an insulating layer formed over said substrate; and
said floating diffusion region being connected to the output transistor by a doped polysilicon conductor formed at least partially within the insulating layer, the doped polysilicon conductor being doped to said first conductivity type, said doped polysilicon conductor being a composite layered doped polysilicon/barrier metal suicide/metal structure. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. An imaging device comprising:
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a substrate;
a photosensitive area within said substrate for accumulating photo-generated charge in said area;
a floating diffusion region in said substrate for receiving charge from said photosensitive area, said floating diffusion region having a first conductivity type at a first concentration, wherein said floating diffusion region comprises a second region of said first conductivity type at a second concentration, said second concentration being greater than said first concentration;
a readout circuit comprising at least an output transistor formed in said substrate;
an insulating layer formed over said substrate;
a doped polysilicon conductor formed in said insulating layer for connecting said floating diffusion region with a gate of said output transistor, said doped polysilicon conductor having a first conductivity type at a third concentration, wherein said third concentration is greater than said first and second concentrations.
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Specification