Patent ID: 9728565
Date: 2017-08-08
CPC Classifications: H01L,Y02E

Claim:
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 (i) a charge accumulation/storage region disposed substantially or entirely beneath the transfer gate and spaced away from the first surface of the semiconductor substrate, and (ii) a pinning region spaced away from the first surface of the semiconductor substrate and disposed laterally to the charge accumulation/storage region and configured to pin the potential of the charge accumulation/storage region, wherein the charge accumulation/storage region has a full-well capacity less than 3000 charge carriers, and substantially all photocharge generated by the photodiode in response to impinging photons is accumulated in the charge accumulation/storage region beneath the transfer gate; and wherein a potential barrier prevents charge transfer between the charge accumulation/storage region and the floating diffusion when a first voltage is applied to the transfer gate, and the potential barrier is reduced or eliminated so as to allow charge transfer between the charge accumulation/storage region and the floating diffusion when a second voltage is applied to the transfer gate, such that the transfer gate is operable to selectively transfer charge from the charge accumulation/storage region to the floating diffusion.