Anti-blooming drain structure in charge coupled device image sensors

摘要

A frame transfer buried channel CCD image sensor incorporating an anti-blooming drain structure (25, 27) wherein accumulation of charge of opposite polarity to that drained by the anti-blooming drain structure is prevented. This can conveniently be achieved by arranging for the buried channel diffusion (19) in each channel to stop short of the anti-blooming drain diffusion (25) on one side of each channel. As a result of the prevention of charge accumulation the anti-blooming drain structure remains effective with optical overloads much greater than the optical overload at which anti-blooming performance begins to deteriorate in conventional buried channel CCD image sensors.