Anti-blooming structures for back-illuminated imagers

An anti-blooming structure for a back-illuminated imager is disclosed. In one embodiment, the anti-blooming structure is formed in a substrate of a first conductivity type having a back side and a front side, comprising a channel region of a second conductivity type formed in the substrate; a barrier region of the first conductivity type positioned in the substrate substantially overlying the channel region and proximal to the front side of the substrate; and a drain region of the second conductivity type positioned substantially overlying the barrier region, wherein when light impinges on the back side of the substrate the light generates charge carriers that collect in the channel region, the charge carriers passing through the barrier region into the drain region when a potential corresponding to the collected charge carriers in the channel region is about equal to the potential corresponding to the barrier region. In a second embodiment, a drain region of the second conductivity type is positioned substantially extending into at least a portion of the front side of the substrate; a barrier region of the first conductivity type positioned substantially underlying about the drain region; and a channel region of the second conductivity type positioned substantially underlying and about the barrier region. The channel region, the barrier region, and the drain region are formed by ion implantation.