Method and image sensor with extended pixel dynamic range incorporating transfer gate with potential well

Abstract

A charge transfer transistor includes: a first diffusion region and a second diffusion region; a gate for controlling a charge transfer from the first diffusion region to the second diffusion region by a control signal; and a potential well incorporated under the gate, wherein the first diffusion region is a pinned photodiode. A pixel of an image sensor includes: a photodiode for generating and collecting a photo generated charge; a floating diffusion region for serving as a photo generated charge sensing node; a transfer gate for controlling a charge transfer from the photodiode to the floating diffusion region by a control signal; and a potential well incorporated under the transfer gate.

1 - 12 . (canceled) 
     
     
         13 . A method, comprising:
 forming a photodiode in a substrate having a first conductivity type;   forming, in the substrate, a floating diffusion region having a second conductivity type;   implanting an impurity of the second conductivity type to form an implantation region in the substrate between the photodiode and the floating diffusion region; and   forming a charge transfer gate on the substrate between the photodiode and the floating diffusion region;   wherein said implanting comprises implanting the implantation region such that the implantation region is positioned under the charge transfer gate and toward a side of the charge transfer gate associated with the floating diffusion region.   
     
     
         14 . The method of  claim 13 , wherein said implanting comprises implanting an N-type impurity to form an N-type impurity region for the implantation region. 
     
     
         15 . The method of  claim 13 , wherein said implanting comprises implanting the implantation region such that the implantation region is not under the floating diffusion region. 
     
     
         16 . The method of  claim 13 , wherein said implanting comprises forming the implantation region such that the implantation region is configured to store a charge from the photodiode, prevent the charge from flowing back to the photodiode, and transfer the charge onto the floating diffusion region in response to turning-off the charge transfer gate. 
     
     
         17 . The method of  claim 13 , further comprising:
 forming a reset transistor configured to reset the floating diffusion region;   forming a source follower transistor configured to amplify a charge signal of the floating diffusion region; and   forming an addressing transistor configured to select an output of the source follower transistor and to provide the selected output as a pixel output.   
     
     
         18 . The method of  claim 13 , further comprising:
 forming another photodiode in the substrate;   implanting the impurity to form another implantation region in the substrate between the other photodiode and the floating diffusion region; and   forming another charge transfer gate on the substrate between the other photodiode and the floating diffusion region;   wherein said implanting the impurity to form another implantation region comprises implanting the other implantation region such that the other implantation region is positioned under the other charge transfer gate and toward a side of the other charge transfer gate associated with the floating diffusion region.   
     
     
         19 . The method of  claim 18 , wherein said implanting the impurity to form another implantation region comprises forming the other implantation region such that the other implantation region is configured to store a charge from the other photodiode, prevent the charge from flowing back to the other photodiode, and transfer the charge onto the floating diffusion region in response to turning-off the other charge transfer gate. 
     
     
         20 . A method, comprising:
 collecting charge with a photodiode;   in response to turning on a charge transfer transistor, transferring charge from the photodiode to both a floating diffusion region and an implantation region that is separate from the floating diffusion region and located under a charge transfer gate of the charge transfer transistor toward a side of the charge transfer gate associated with the floating diffusion region; and   in response to turning off the charge transfer transistor, transferring charge from the implantation region to the floating diffusion region.   
     
     
         21 . The method of  claim 20 , further comprising resetting the floating diffusion region prior to said transferring charge from the photodiode to both the floating diffusion region and the implantation region. 
     
     
         22 . The method of  claim 20 , further comprising generating an output signal indicative of charge received by the floating diffusion region from the photodiode and the implantation region. 
     
     
         23 . The method of  claim 20 , further comprising:
 collecting charge with another photodiode;   in response to turning on another charge transfer transistor, transferring charge from the other photodiode to both the floating diffusion region and another implantation region that is separate from the floating diffusion region and located under another charge transfer gate of the other charge transfer transistor toward a side of the other charge transfer gate associated with the floating diffusion region; and   in response to turning off the other charge transfer transistor, transferring charge from the other implantation region to the floating diffusion region.   
     
     
         24 . The method of  claim 23 , further comprising resetting the floating diffusion region prior to said transferring charge from the other photodiode to both the floating diffusion region and the other implantation region. 
     
     
         25 . The method of  claim 23 , further comprising generating an output signal indicative of charge received by the floating diffusion region from the other photodiode and the other implantation region. 
     
     
         26 . A method, comprising:
 transferring charge from a photodiode to both a floating diffusion region and a charge collection region that is separate from the floating diffusion region in response to a first control signal; and   transferring charge from the charge collection region to the floating diffusion region in response to a second control signal.   
     
     
         27 . The method of  claim 26 , further comprising, in response to the first control signal, turning on a charge transfer transistor to transfer charge from the photodiode to both the floating diffusion region and the charge collection region. 
     
     
         28 . The method of  claim 27 , further comprising, in response to the second control signal, turning off the charge transfer transistor to transfer charge from the charge collection region to the floating diffusion region. 
     
     
         29 . The method of  claim 26 , further comprising, in response to the first control signal, turning on a charge transfer transistor to transfer charge from the photodiode to both the floating diffusion region and the charge collection region located under a charge transfer gate of the charge transfer transistor and toward the floating diffusion region. 
     
     
         30 . The method of  claim 26 , further comprising:
 transferring charge from another photodiode to both the floating diffusion region and another charge collection region that is separate from the floating diffusion region and the charge collection region in response to a third control signal; and   transferring charge from the other charge collection region to the floating diffusion region in response to a fourth control signal.   
     
     
         31 . The method of  claim 30 , further comprising, in response to the third control signal, turning on another charge transfer transistor to transfer charge from the photodiode to both the floating diffusion region and the other charge collection region located under a charge transfer gate of the another charge transfer transistor and toward the floating diffusion region. 
     
     
         32 . The method of  claim 31 , further comprising, in response to the fourth control signal, turning off the other charge transfer transistor to transfer charge from the other charge collection region to the floating diffusion region.