Small pixel for CMOS image sensors with vertically integrated set and reset diodes

摘要

A pixel of an image sensor, the pixel includes a floating diffusion node to sense photo-generated charge, a reset diode to reset the floating diffusion node in response to a reset signal, and a set diode to set the floating diffusion node.

主权项

1. A method for making a pixel of an image sensor, the method comprising:
forming a floating diffusion node in a substrate; forming a dielectric layer over the floating diffusion node, where the dielectric layer includes an opening extending vertically through the dielectric layer to the floating diffusion node; and forming a vertically-oriented reset diode in the opening such that the reset diode is in contact with the floating diffusion node, wherein said forming a vertically-oriented reset diode includes
forming a first vertical portion of the vertically-oriented reset diode by depositing a doped semiconductor of a first doping level of a given doping type in electrical contact with the floating diffusion node; andforming a second vertical portion of the vertically-oriented reset diode by depositing a doped semiconductor of a second doping level of the given doping type, wherein the second vertical portion is in electrical contact with the first vertical portion, and wherein the second doping level is greater than the first doping level.