CMOS IMAGE SENSOR WITH PUMP GATE AND EXTREMELY HIGH CONVERSION GAIN

摘要

Some embodiments relate to an image sensor pixel comprising a transfer gate formed on a first surface of a semiconductor substrate, a floating diffusion formed in the first surface of the semiconductor substrate, and a buried-well vertically pinned photodiode having a charge accumulation/storage region disposed substantially beneath the transfer gate. The transfer gate is spaced away from the floating diffusion such that an intervening semiconductor region provides a potential barrier to charge flow from beneath the transfer gate to the floating diffusion. The transfer gate is operable to control a vertical pump gate to selectively transfer charge from the charge accumulation/storage region to the floating diffusion by pumping charge from the buried charge accumulation/storage region underlying the transfer gate, over the potential barrier, and out to the floating diffusion, such that full charge transfer can be achieved without overlapping the edge of the transfer gate with the floating diffusion.

主权项

1. An image sensor comprising a plurality of pixels, each pixel comprising:
a transfer gate formed on a first surface of a semiconductor substrate; a floating diffusion region formed in the first surface of the semiconductor substrate; and a buried-well vertically pinned photodiode having a charge accumulation/storage region disposed substantially beneath the transfer gate, wherein the transfer gate is spaced away from the floating diffusion region such that an intervening semiconductor region provides a potential barrier to charge flow from beneath the transfer gate to the floating diffusion, and wherein the transfer gate is operable to control a vertical pump gate to selectively transfer charge from the charge accumulation/storage region to the floating diffusion by pumping charge from the buried charge accumulation/storage region underlying the transfer gate, over the potential barrier that is between the transfer gate and the floating diffusion region, and out to the floating diffusion region, such that full charge transfer can be achieved without overlapping the edge of the transfer gate with the floating diffusion region.