CMOS imager and method of formation
AssigneeMicron Technology, Inc.
InventorHoward E. Rhodes
Life of this patent
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Abstract
One or more deep-array implants under the photosensitive region of a semiconductor substrate are conducted to improve optical cross-talk between pixel cells. According to an embodiment of the present invention, one or more deep-array implants of a first conductivity type are used to dope predefined regions of a well of a second conductivity type. This way, first conductivity type dopants from the one or more deep-array implants counterdope second conductivity type dopants from the predefined regions of the well. The dosage and energy of each deep-array implant may be optimized so that the collection of signal carriers by the photosensitive region and the photoresponse for different wavelengths are maximized.
Claims80
A color pixel cell for an imaging device, said color pixel cell comprising:
- a well of a first conductivity type formed in a substrate;
- a first, second and third doped regions formed in said well, at least one of said first, second and third doped regions having a different doping concentration than another of said doped regions;
- a first, second and third photosensitive regions formed in said respective first, second and third doped regions for receiving first, second and third photocharges corresponding to a particular color wavelength;
- and
- a first, second and third floating diffusion regions of a second conductivity type formed in said respective first, second and third doped regions for receiving said respective photocharges transferred from said respective first, second and third photosensitive regions.
The color pixel cell of claim 4 wherein said first doped region has a different dopant concentration form said third doped region.
The color pixel cell of clam 16, wherein each of said photosensor is a photoconductor sensor.
A color pixel cell for an imaging device, said color pixel cell comprising:
- a red pixel cell, a blue pixel cell and a green pixel cell, each comprising a respective first, second and third regions of a well of a first conductivity type formed in a substrate, said first region having a different doping concentration in said substrate than said second and third regions;
- a photosensor formed in each one of said first, second and third regions for sensing respective red, blue and green color wavelengths;
- a reset transistor having a gate stack formed in each one of said first, second and third regions;
- a floating diffusion region of a second conductivity type formed in each one of said first, second and third regions between said photosensor and said reset transistor for receiving charges from said photosensor, said reset transistor operating to periodically reset a charge level of said floating diffusion region;
- and
- an output transistor having a gate electrically connected to said floating diffusion region.
A CMOS imager comprising:
- a substrate having a first, second and third regions of a first conductivity type, said first, second and third regions each having a different doping concentration in said substrate from the other regions, and wherein each of said first, second and third regions has a respective photosensor formed therein for sensing respective red, blue and green color wavelengths;
- an array of pixel sensor cells formed in said first, second and third regions;
- and
- a circuit electrically connected to receive and process output signals from said array.
An imager comprising:
- an array of color pixel cells formed in a substrate having at least one well of a first conductivity type and having a first doping concentration, and at least one region of said well having a second doping concentration which is lower than said first doping concentration, and wherein each pixel sensor cell has a photosensor for sensing a respective particular color wavelength;
- a circuit formed in said substrate and electrically connected to said array for receiving and processing signals representing an image output by said array and for providing output data representing the image;
- and
- a processor for receiving and processing data representing the image.
A method of forming photosensors for an imaging device, said method comprising the steps of:
- forming a well of a first conductivity type in a substrate, said well having a first doping concentration;
- conducting at least one implant of a second conductivity type in at least a region of said well to form at least one doped region, said at least one doped region having a second doping concentration which is lower than said first doping concentration;
- and
- forming at least one photosensor for sensing charges of a particular color wavelength at an upper surface of said at least one doped region.
A method of forming a color pixel cell for an imaging device, said method comprising the steps of:
- forming a well of a first conductivity type in a substrate;
- forming at least three doped regions of said first conductivity type in said substrate, said at least three doped regions having different doping concentrations in said well;
- forming a photosensitive region in each of said at least three doped regions;
- forming a photosensor on an upper surface of said photosensitive region for receiving charges of a particular color wavelength;
- and
- forming a floating diffusion region of a second conductivity type in each one of said at least three doped regions for receiving charges transferred from said photosensitive region in the same well.
A method of forming a pixel array for an imaging device, said method comprising the steps of:
- forming multiple dopant regions in a well of a substrate, said well and said multiple dopant regions having a first conductivity type, said multiple dopant regions having different dopant concentrations;
- and
- forming a plurality of pixel sensor cells in said multiple dopant regions, wherein each pixel sensor cell has a photosensitive region, a photosensor formed on said photosensitive region for sensing charges of a particular color wavelength, and a floating diffusion region of a second conductivity type.
Dependencies are inferred from the claim text.