超快电荷转移的大尺寸PPD像素器件设计

Design of Large-size PPD Pixel Device with Ultra-fast Charge Transfer

摘要:

面向微光环境的高时间分辨成像需求,基于CMOS图像传感器工艺,设计并仿真验证了一种具有三角形状梯度掺杂且浮置扩散区域中置的超快电荷转移大尺寸光电二极管(PPD)像素器件。它通过N埋层掺杂形状和梯度掺杂设计增强光生电荷传输路径的电势梯度,加速光生电荷从N埋层感光区域向电荷存储区域的转移。同时通过对传输管沟道的梯度掺杂,减小了沟道反弹电荷的水平,有效提升了光生电荷转移效率。仿真结果表明,三角形枝状的圆形像素器件在30000个电荷的情况下,在电荷转移效率达到99.9%时,电荷转移时间为1ns,同时其反弹电荷水平在1e-以下。该PPD像素器件可用于微光环境下的高时间分辨率成像。

Abstract:

Aiming at the needs of high time resolution imaging in low light environment, based on CIS process, a large-size PPD pixel device with ultra-fast charge transfer is designed and simulated, which owns a gradient-doped triangular shape and central floating diffusion region. The doping shape and gradient doping of the N-buried layer can enhance the gradient potential formed on the transmission path, thereby the transfer of the photo-generated charge from the Nburied layer to the charge storage area will be accelerated. At the same time, by making the gradient doping of the transfer transistor channel, the rebound charge is reduced and the transfer efficiency is effectively improved. Simulation results show that the charge transfer time is 1ns and the rebound charge level is below 1e- when the triangular branch-shaped circular pixel device contains 30,000 charges and the charge transfer efficiency reaches 99.9%. Thus, the PPD pixel device can be used for high time resolution imaging in low light environment.