TOF image sensor demodulation pixel structure with rapid charge transfer

Abstract

The present invention discloses a TOF image sensor demodulation pixel structure with rapid charge transfer. The structure comprises a PPD-based dual-floating-diffusion-node 4T pixel unit which comprises two transfer tubes responsible for transferring photocharges from a PPD to double FD nodes and is characterized in that multiple adjacent polysilicon gates with a minimum width are employed by a gate of each of the transfer tubes, the multiple polysilicon gates are connected to a resistor array and are powered by the resistor array such that the polysilicon gates have increasing gate voltages,and the gate voltages are coupled to a semiconductor through a capacitor to form a lateral drift electric field. According to the invention, the gates of the polysilicon gates are substituted with multiple adjacent polysilicon gates with the minimum width, the increasing gate voltages are applied to the gates to form the lateral drift field of the photocharges under the gates of the transfer tubes, and the transfer of the photocharges is accelerated.

Description

technical field [0001] The invention relates to the technical field of image sensors, in particular to a demodulation pixel structure of a TOF image sensor with fast charge transfer. Background technique [0002] In the TOF image sensor demodulation pixel structure based on clamped photodiode (pinned photodiode, PPD), the photocharge transmission from PPD to FD node is controlled by the diffusion effect in the semiconductor, and the photocharge generated by PPD can only pass through the semiconductor. Diffusion is transferred, which seriously affects the transfer speed of photoelectric charges, which limits the use of pixels at high modulation frequencies. Due to the slow diffusion process, it will affect the performance of PPD. Some solutions obtain a larger photosensitive area by changing the shape of the device to increase the generation of photocharges; there are also solutions that increase the injection of impurities in the photosensitive area to optimize PDD performan...

AI Technical Summary

Problems solved by technology

[0002] In the TOF image sensor demodulation pixel structure based on clamped photodiode (pinned photodiode, PPD), the photocharge transmission from PPD to FD node is controlled by the diffusion effect in the semiconductor, and the photocharge generated by PPD can only pass through the semiconductor. Diffusion is transferred, which seriously affects the transfer speed of photocharges, which limits the use of pixels at high modulation frequencies. Due to the slow diffusion process, it will affect the performance of PPD

Images