Charge-coupled imager with dual gate anti-blooming structure

摘要

A CCD imager includes a substrate of a semiconductor material having a plurality of photodetectors therein at a top surface thereof and arranged either in a line or in an array of rows and columns. A CCD shift register is in the substrate along but spaced from one side of the line or each column of photodetectors. Between each photodetector and its adjacent shift register is an accumulation region. A transfer gate is provided between the shift register and its adjacent line or column of accumulation regions. A transfer gate is provided between each line or row of photodetectors and the adjacent accumulation regions. A first anti-blooming drain region is provided along each line or column of photodetectors on the side of the photodetectors opposite the accumulation regions. A separate second anti-blooming drain is provided along a side of each accumulation region in the area of the substrate between the shift register and the photodetectors. During the integration stage of the imager while charge carriers generated in the photodetectorsa are being collected and stored in the accumulation regions, any excess charge carriers flow into the second anti-blooming drains to prevent blooming into the shift register. During the transfer stage when the charge carriers are being transferred to the shift register, excess charge carriers generated in the photodetectors flow into the first anti-blooming drain to prevent blooming in the shift register during the transfer stage.