Active pixel sensor integrated with a pinned photodiode
AssigneeEastman Kodak Company
InventorsPaul P. Lee, Robert M. Guidash, Teh-Hsuang Lee, Eric G. Stevens
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Abstract
The optimization of two technologies (CMOS and CCD) wherein a pinned photodiode is integrated into the image sensing element of an active pixel sensor. Pinned photodiodes are fabricated with CCD process steps into the active pixel architecture. Charge integrated within the active pixel pinned photodiode is transferred into the charge sensing node by a transfer gate. The floating diffusion is coupled CMOS circuitry that can provide the addressing capabilities of individual pixels. Alternatively, a buried channel photocapacitor can be used in place of the pinned photodiode.
Claims15
An active pixel sensor having at least one pinned photodiode comprising:
- a semiconductor material of a first conductivity type having a series of masking layers including at least one conductive layer, and at least one charge sensing means;
- at least one transfer gate and a series of local interconnections upon the conductive layer;
- a first set of implants made from a second conductivity type that is opposite the first conductivity type, the first set of implants functioning as sources and drains for a first set of transistors, including at least one source for each of the transfer gates such that the drain is self aligned to the transfer gate;
- at least one image sensing area adjacent to the transfer gate formed from one of the sources implanted within the substrate to create a photodiode, with a pinning layer comprising a material of the first conductivity type on top of the photodiode;
- a second set of implants used as sources and drains for a second set of transistors made from implants of the first conductivity type, the second set of transistors being formed in conjunction with any remaining the first set of transistors that were not used to create image sensors to form a CMOS control circuit coupled to the image sensor by the local connection;
- and
- a predetermined set of contacts on first and second set of source drains.
A pinned photodiode integrated within an image sensing element comprising:
- a substrate of semiconductor material made from a first conductivity type;
- a plurality of regions of a second conductivity type that is opposite the first conductivity type formed within the substrate, such that there is at least one image sensing region and at least one image transferring region and at least one charge sensing well for each of a plurality of image sensing pixels;
- a transfer region formed as a buried channel layer from the second conductivity type between the image sensing region and the image transferring region within each of the pixels;
- a pinned photodiode formed upon the image sensing region from ions of the first conductivity type such that at least one edge of the pinned photodiode is self aligned to a side of the transfer gate adjacent to the photodiode;
- a charge sensing node region formed within each of the pixels from one of the image transferring regions adjacent to the transfer region;
- a transfer gate for controlling charge flow from the pinned photodiode to the charge sensing node region;
- a plurality of regions of the first conductivity type formed within the substrate, functioning as sources and drain for a second set of transistors;
- and
- means for coupling the charge sensing node region to the second set of transistors.
An active pixel image sensor comprising:
- a pinned photodiode operatively coupled to CMOS control circuitry.
Dependencies are inferred from the claim text.