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US 7,071,505 B2Granted
Method and apparatus for reducing imager floating diffusion leakage
AssigneeMicron Technology, Inc.
InventorHoward E. Rhodes
Life of this patent
Estimating the term…
Abstract
An imager having reduced floating diffusion leakage and a mechanism for improving the storing of collected charge is described. A polysilicon contact is provided between a floating diffusion region and a gate of a source follower output transistor, with the contact also electrically connected to a storage capacitor. The storage capacitor provides additional charge storage capacity to the floating diffusion region. In addition, an associated reset transistor has different dopant characteristics in the source and drain regions. The floating diffusion region may be used in the pixels of a CMOS imager or in the output stage of a CCD imager.
Claims76
A pixel sensor cell comprising:
- a charge collection area for receiving photo-generated charges from a photoconversion device;
- a polysilicon contact doped to a first conductivity type and located over and electrically connected to said charge collection area;
- a storage capacitor connected to said charge collection area through said contact;
- and
- a source follower transistor, wherein said contact further connects said charge collection area to said source follower transistor.
2 more elements
An imager circuit comprising:
- a charge collection area for receiving photo-generated charges from a photoconversion device;
- a transistor coupled to said charge collection area such that said charge collection area acts as a source/drain region of said transistor, said source/drain region being of a first conductivity type;
- and
- a polysilicon contact doped to said first conductivity type and located over and electrically connected to said charge collection area, said contact connecting said charge collection area to a source follower transistor and to a storage capacitor.
1 more element
A pixel sensor cell comprising:
- a photoconversion device;
- a charge collection area of a first conductivity type for receiving photo-generated charges from said photoconversion device;
- a reset transistor coupled to said charge collection area such that said charge collection area acts as a first source/drain region of said transistor, said transistor having a second source/drain region including a first region of said first conductivity type and a second region of a second conductivity type, one of the doping concentration and conductivity type, of said second source/drain region being different than that of said first source/drain region;
- and
- a storage capacitor connected to said charge collection area through a contact.
2 more elements
A pixel sensor cell comprising:
- a photoconversion device;
- a charge collection area of a first conductivity type for receiving photo-generated charges from said photoconversion device;
- a transistor coupled to said charge collection area such that said charge collection area acts as a first source/drain region of said transistor, said transistor having a second source/drain region including a first region of said first conductivity type and a second region of a second conductivity type, one of the doping concentration and conductivity type of said second source/drain region being different than that of said first source/drain region;
- and
- a polysilicon contact located over and electrically connected to said charge collection area.
2 more elements
A processing system comprising:
- a processor;
- and
- an imager coupled to said processor, said imager comprising:
- a charge collection area of a first conductivity type for receiving photo-generated charges from a photoconversion device;
- a transistor coupled to said charge collection area such that said charge collection area acts as a first source/drain region of said transistor, said transistor having a second source/drain region including a first region of said first conductivity type and a second region of a second conductivity type, one of the doping concentration and conductivity type of said second source/drain region being different than that of said first source/drain region;
- a polysilicon contact doped to said first conductivity type and located over and electrically connected to said charge collection area;
- and
- a storage capacitor connected to said charge collection area through said contact;
- and
- a readout circuit comprising at least an output transistor.
7 more elements
An imager comprising:
- an array of pixel sensor cells formed in a doped layer, wherein each pixel sensor cell comprises a photoconversion device;
- a charge collection area of a first conductivity type for receiving photo-generated charges from said photoconversion device;
- a transistor coupled to said charge collection area such that said charge collection area acts as a first source/drain region of said transistor, said transistor having a second source/drain region including a first region of said first conductivity type and a second region of a second conductivity type, one of the doping concentration and conductivity type of said second source/drain region being different than that of said first source/drain region;
- a polysilicon contact doped to said first conductivity type and located over and electrically connected to said charge collection area;
- a storage capacitor connected to said charge collection area through said contact;
- and
- signal processing circuitry electrically connected to said array for receiving and processing signals representing an image output by said array and for providing output data representing said image.
4 more elements
A method of forming an imager comprising:
- forming a first transistor coupled to a charge collection area of a first conductivity type such that said charge collection area acts as a first source/drain region of said transistor, said first transistor having a second source/drain region including a first region of the first conductivity type and a second region of a second conductivity type, one of the doping concentration and conductivity type of said second source/drain region being different than that of said first source/drain region;
- forming a storage capacitor connected to said charge collection area;
- and
- forming a polysilicon contact connecting said charge collection area to said storage capacitor and an output to a gate of a source follower transistor.
1 more element
A method of forming an imager comprising:
- forming a first transistor coupled to a charge collection area of a first conductivity type such that said charge collection area acts as a first source/drain region of said transistor, said first transistor having a second source/drain region including a first region of the first conductivity type and a second region of a second conductivity type, one of the doping concentration and conductivity type of said second source/drain region being different than that of said first source/drain region;
- and
- forming a polysilicon contact connecting said charge collection area to a source follower transistor.
A method of forming an imager comprising:
- forming a first transistor coupled to a charge collection area of a first conductivity type such that said charge collection area acts as a first source/drain region of said transistor, said first transistor having a second source/drain region including a first region of the first conductivity type and a second region of a second conductivity type, one of the doping concentration and conductivity type of said second source/drain region being different than that of said first source/drain region;
- and
- forming a storage capacitor connected to said charge collection area.
Dependencies are inferred from the claim text.