Image sensor with controllable vertically integrated photodetectors

A method for reading charge out of a pixel in an image sensor comprising a plurality of pixels, wherein the pixel includes a front-side photodetector of a first conductivity type disposed in a substrate layer of the first conductivity type adjacent to a front-side of the substrate layer, a backside photodetector of a first conductivity type disposed in the substrate layer adjacent to a backside of the substrate layer, a front-side pinning layer of a second conductivity type spanning the front-side photodetector, a backside pinning layer of the second conductivity type spanning the backside photodetector, a front-side charge to voltage conversion region of the first conductivity type disposed in a front-side well of the second conductivity adjacent to the front-side photodetector, a backside barrier region of the second conductivity type disposed in the substrate layer adjacent to the backside photodetector, and a lateral overflow drain of the first conductivity type disposed in the backside barrier region, the method comprising:

• setting the front-side pinning layer to a first potential;
• producing an electrostatic barrier between the front-side photodetector and the backside photodetector by adjusting an adjustable and programmable second potential on the backside pinning layer to a second potential;
• producing an electrostatic barrier between the backside photodetector and the backside lateral overflow drain by adjusting an adjustable and programmable third potential on the backside lateral overflow drain to a third potential, wherein the electrostatic potential between the backside photodetector and the backside lateral overflow drain is lower than the electrostatic potential between the front-side and backside photodetectors;
• capturing an image by collecting photogenerated charge in the backside photodetector;
• removing the electrostatic barrier between the backside photodetector and the front-side photodetector and adjusting the electrostatic barrier between the backside photodetector and the backside lateral overflow drain and transferring the charge from the backside photodetector to the front-side photodetector by adjusting the adjustable and programmable second and third potentials to different potentials;
• returning the adjustable and programmable second potential to the second potential;
• returning the adjustable and programmable third potential to the third potential;
• and
• transferring the charge from the front-side photodetector to the charge to voltage conversion region.